Shoud I relieve my block

[Ol' Ron]

The answer is: absolutely not!!!! The internet as posted several articles on relieving the flathead block. I did allot of this in the early days, untill I went racing, and discovered the fact that very few builders did this. In a conversation with a builder of a few good winning engines , stated there was no real information of the benefits of relieving the block and it was time consuming and a pain in the ass to install the pistons, PLUS no prof that it increased power or economy,
Gramps

[Seth Swoboda]

I would never do it based on the lower CR. Some folks get a big kick out of a relieved block. I had a relieved block and sold it. I was glad to see it go. I agree with you Ron.

[19Fordy]

It's a relief not to relieve.

[V8COOPMAN]

.

I must admit that I would never go to the expense in time or money of relieving a block. But with that being said, I've still gotta ask WHY did those Frenchmen go to the trouble on those beautiful French flatheads (one of which I just sold the last couple of days), as well as the relatively few that Henry Ford produced for buses and other industrial equipment?

Coop

[Jack E/NJ]

Some claim if the exhaust is left alone and the intake relieved a bit, good things might happen.

[Pete]

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I would not bother on a mild street engine but I can get well over 1 hp per cubic inch naturally aspirated on gas in a race engine.
The relief is as deep and wide as the block material will permit. The pistons are flat.

[cadillac512]

Originally Posted by Pete

I would not bother on a mild street engine but I can get well over 1 hp per cubic inch naturally aspirated on gas in a race engine.
The relief is as deep and wide as the block material will permit. The pistons are flat.

Is the head flat as well,Pete? Good compression.

[Ronnieroadster]

Like Pete wrote for a mild street engine there's no need. However if your interested in getting some more power and economy taking the time to do it correctly is worth the effort. We know Ford did do it on engine's going into Ford trucks makes you wonder why. And as Coop points out the French flathead blocks all had the relief's. Plus as an added point of interest the one flathead design that produced a LOT of power and I would expect economy if needed was the Harley Davidson KR headed flatheads with a relief and that was in the 1960's era.
Like Pete wrote 1 HP per cubic inch out of a Ford flathead is easily possible its being done everyday.

The slight amount of compression reduction caused due to the block being relived in a flathead is actually a good thing considering the poor quality of the gas we have today. High compression and to much timing is a killer for a Flathead unless your burning a good quality high octane gas if your are than your good to go.
Ronnieroadster

[Graeme / New Zealand]

I have a 99A block sitting under a tarp that is factory relieved.

GB

[Pete]

Originally Posted by cadillac512

Is the head flat as well,Pete? Good compression.

The head is flat also. The transfer area in the head is adjusted for compression ratio.

I can get 14 to 1 compression ratio for running alcohol.

[Ol' Ron]

I've run some flow test on cumbustion chamber design, and as airflow speeds increas so does the turbulence caused by chamber irregularities. overt 4500 RPN The turblance increase dreamily and the valve bowl is the worst. One reason the torque drops after 4500 rpm. John and I talked about it when he as buildinng his Bvill engine and he came uo with the new guides which helped this area. Photos in his book. I'll post some computer flow graphs, but can't be sure of their accuracy
Gramps

[mcharley40]

I’m no expert however I do have bunch of old literature from early days of Harley Davidson on their development of the side valves. All their successful racing engines had a relief area.
Hopping up Ford Flatties seem to follow suit. Ron you have real knowledge of real testing.
Good enough for me.

[Bored&Stroked]

I have original Harley KR jugs and heads - they were relieved and also had a very different head design. They ran mostly flat-top pistons until later in the 60's when they tried a dome top. The dome top engines didn't make any more HP than the flat-topped piston designs. Of course, these were purpose built racing engines and ran way past 6000 RPM all the time. Flow was everything to their design, with huge ports, big valves, etc.. We only wish our Ford flatheads had anywhere near the type of ports and head-bolt layouts of the Harleys.

When I designed our FlatCAD chambers, heads and pistons (flathead Cadillac Bonneville engine) - we used as much of the 'KR' design as possible - including the custom mods that Jerry Branch made for his modified KR's.

Branch (and my neighbor 'Snuffy Smith') made some of the highest HP KR's of the day. I learned a LOT from Snuffy! Snuffy built a KR for use at Daytona for a rich guy back in the early 90's - was making about 60 HP on a 45 cube KR on gas. The guys running the dyno were really surprised about the HP he was able to achieve on the good ole' KR sidevalve motor.

[Bored&Stroked]

Here is a picture of a KR head - for flat top pistons - the piston popped up about 3/16" of an inch into the chamber. This was very important for flow:

KR.jpg

Here is a picture of the Navarro Hi-Flo head - which used some of the KR type design (stepped relief):

DSC00521.jpg

Here is a Tony Baron "Pop-UP" head - using a very tall pop-up piston design:

BaronPopUp.jpg


Here is a picture of the 3D CAD Model for the FlatCAD chambers:

HEAD-Final9b_CNC_mockup.1.jpg

Here is the actual FlatCAD Head Chamber:

Chamber.1.jpg

[Ol' Ron]

Well I guess I'm wrong. I'd like to see a flathead that makes one HP per cubic inch flathead on gas. I nolonger have the eqipment I used for my testing, so I can't comment on these reselts with any acury. I agree with the HD engine design as we looked at it back then. The Grancore heads were similar with a pop up piston. someone out there has them, Ford factory relieved blocks didn't last long and were designed to limit detention. I was told. But they never included it in the late engines or the 337. The French were just copying it.
Everybody has an excuse for their actions and beliefs , I stand corrected.
Gramps

[Jack E/NJ]

RR>>1 HP per cubic inch out of a Ford flathead is>>done everyday.>>


O'R>>Well I guess I'm wrong. I'd like to see a flathead that makes one HP per cubic inch flathead on gas. >>>



Maybe not Ol'Ron.. Prolly only done every other day.

[Pete]

For those that keep saying they would like to see a flathead Ford race engine that makes over 1 hp per cubic inch naturally aspirated on gas, I would like to tell you how simple that is.
First off, you will see the engine and car but you will not see inside the engine. These engines are seldom torn down at the track unless it is for record certification and unless you are a VERY good friend of the owner, you are not going to see much.
To see one of these engines, you must first find out what cars they run in by looking up records set at the various tracks they run at. This is easily done by looking up land speed racing tracks in the USA. There are several beside Bonneville.
When you find where they are running you contact the car owner and find when he is going to run, Then you go watch.
These engines have been around since the 50's so they are really nothing new.

[Bored&Stroked]

Originally Posted by Ol' Ron

Well I guess I'm wrong. I'd like to see a flathead that makes one HP per cubic inch flathead on gas. I nolonger have the eqipment I used for my testing, so I can't comment on these reselts with any acury. I agree with the HD engine design as we looked at it back then. The Grancore heads were similar with a pop up piston. someone out there has them, Ford factory relieved blocks didn't last long and were designed to limit detention. I was told. But they never included it in the late engines or the 337. The French were just copying it.
Everybody has an excuse for their actions and beliefs , I stand corrected.
Gramps

Actually, you were not wrong - it is all about the application and usage of the engine. Relieving a Ford Flathead does nothing of value before about 4000 - 4500 RPM . . . actually it hurts low end power as it reduced compression (with everything else the same). Also, relieving is just one small piece of the overall puzzle - you have the ports to worry about (they take serious amounts of work), you have the cam to worry about, you have the valves, the chambers in the heads, etc.. As Pete noted - when all the things are specifically designed to work together (for racing) - then relieving is part of the "combo" that was typically used.

Also, typically these naturally aspirated engines were fuel injected - which surely adds horsepower over the typical Stromberg setup. And truth be told, the classical Hilborn flathead injector is too small for max HP. Guys like Don Ferguson Sr. cast their own injectors way back in the 80's - with big port/butterfly sizes more like a SBC injector (to get the flow they needed).

Then, one can start talking about oil-control, dry-sumps, crank scrapers, vacuum pumps, low-tension rings, straight-cut cam gears, etc.. A lot can go into one of these engines - and it is not for those "on the cheap".

[tubman]

Oh, so it's the old : "I could tell ya', but then I'd have to kill ya'".

[38 coupe]

I have the same understanding as Ron, the factory relief was an effort to limit detonation by lowering compression in truck engines, not an effort to improve power. Note that this method of lowering compression preserves the quench between the piston and head and doesn't suffer from the misery that was the 1970s attempts at the same thing by using dished pistons.

Ford flathead V8 chamber design is an interesting subject, and most of the top racing engine builders will not share what their development looks like. Kudos to Bored&Stroked for doing that.
I stumbled on another flathead Ford racing chamber design earlier this year while wandering around the Model T regions of the world wide web. Apparently one of the Kloth combustion chambers from the race motor in the celebrated 1950 Mercury sedan got used as the design for a new Model T high compression head. Link to the web page here: http://hcgarage.net/T-Head.htm
Picture of the combustion chamber, note the larger portion of the chamber is on the intake side:

[Ronnieroadster]

Here's one of them Ford flathead speed secrets learned some time ago a built not relived Ford flathead will rev to 5 grand. To get another thousand RPM a relief will get you there. And to get even more pay attention to what Dale wrote above.
Ronnieroadster

[Pete]

Originally Posted by tubman

Oh, so it's the old : "I could tell ya', but then I'd have to kill ya'".

Well, actually, I have seen on both this and the HAMB forums, a few years ago, pictures of several of the top fuel drag engines with the heads off.
In the old days I saw the Bean Bandits engine with the heads off several times.
Also several other record setters of the day.
The info is out there if people really want to get it.

The thing is, most people can not tell what they are looking at even if they have a caliper and can measure things. Modifying a certain area by even .010 can lose you 5 hp. Few people can discern .010 with the naked eye.

[Ol' Ron]

With the Gas allowed at Bvill I can't see that running ON14: 1 CR I know John looked at allot of chambers, His displacement was alittle over 300 not sure what and the Cr around 12 :1 I know what the power was, ans it was nowhere near 1 per cubic inch. Just what kind of gas do you run on 14:1Cr???? Or is that a secret also/???
Gramps

[Pete]

I don't think that any of my modern engines have run at Bonneville.
They are circle track engines for vintage racing.

Most run alcohol but I do know that a couple run 118 race gas because of rules.
It works fine.
I ran the old discontinued 115/145 av gas in the 50's and it worked fine also.
Gas is usually down in hp about 10% from alcohol.

[richard crow]

if you want a fast car buy a corvet. the more you do to a flathead the worst it runs if you want a smooth cool running eng leave it stock

[Jack E/NJ]

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RR>>Here's one of them Ford flathead speed secrets learned some time ago a built not relived Ford flathead will rev to 5 grand. To get another thousand RPM a relief will get you there.>>>


Interesting. I'd hafta guess that the Hudson racing cognoscenti had a few secrets like this as well.

[Ronnieroadster]

Ron at Bonneville VP racing fuels brand is the gas available.
Anyone running for a gas record must use the VP gas. Example of the octane grades available C-16 has an octane rating of 116 for compression ratios up to 17.1.
The actual altitude at Bonneville is just over 4000 feet for a flathead that has a hard time breathing at sea level this of course is a big issue. I've read for every 1000 feet of altitude an engine can see a reduction in power of 15 percent.
When other factors are added in the density altitude gets even worse early morning at Bonneville the density altitude is just under 6000 feet. That's why the backup runs for a record at Bonneville are held early morning so our engine's have the the best air possible.

Here's one example and some details from the fastest run to date we made with our stock block Ford flathead
{Note stock block means we use the three exhaust ports on each side of the block as designed we do not add any other exhaust port}

Our flathead is 292 cubes we burn C-16 VP gas the car weight is well over 3000 pounds.
The density altitude just after 2 PM in the afternoon was over 7000 feet the Ford flathead engine turning 6100 RPM ran 219.8 MPH . To get a speed this fast burning gasoline takes horsepower lots of it we always run a block relief to help the combination to survive. Hopefully this information will help others in the future who may one day decide to try and do this crazy stuff some of us are doing.
Ronnieroadster

[Ronnieroadster]

Originally Posted by richard crow

if you want a fast car buy a corvet. the more you do to a flathead the worst it runs if you want a smooth cool running eng leave it stock

Well I'm sure there's a few flathead blocks around that would easily put some agent orange corvet to shame in a side by side run
Ronnieroadster

[mhsprecher]

I don't know, but the Beach Boys seemed to think it made a difference. ;-)

Little Deuce Coupe, you don't know what I've got
(You don't know what I've got)
Little Deuce Coupe, you don't know what I've got
Well, I'm not bragging, babe, so don't put me down (Deuce Coupe)
But I've got the fastest set of wheels in town (Deuce Coupe)
When something comes up to me, he don't even try (Deuce Coupe)
'Cause if it had a set of wings, man, I know she can fly
She's my little Deuce Coupe
You don't know what I've got
Little Deuce Coupe
You don't know what I've got
Just a little Deuce Coupe with a flathead mill (Deuce Coupe)
But she'll walk a Thunderbird like it's standing still (Deuce Coupe)
She's ported and relieved, and she's stroked and bored (Deuce Coupe)
She'll do a hundred and forty in the top end floored
She's my little Deuce Coupe
You don't know what I've got
(She's my little Deuce Coupe)
(You don't know what I've got)
She's got a competition clutch with four on the floor
And she purrs like a kitten 'til the lake pipes roar
And if that ain't enough to make you flip your lid
There's one more thing, I've got the pink slip, Daddy
And coming off the line when the light turns green (Deuce Coupe)
Well, she blows 'em outta the water like you've never seen (Deuce Coupe)
I get pushed out of shape, and it's hard to steer (Deuce Coupe)
When I get rubber in all four gears
She's my little Deuce Coupe
You don't know what I've got
(She's my little Deuce Coupe)
(You don't know what I've got)
She's my little Deuce Coupe
You don't know what I've got
(She's my little Deuce Coupe)
(You don't know what I've got)
She's my little Deuce Coupe
You don't know what I've got, what I've got

[flatford8]

This whole thread was great reading on a cold rainy day......Thanks guys!!.......Mark

[John R]

Originally Posted by Bored&Stroked

Actually, you were not wrong - it is all about the application and usage of the engine. Relieving a Ford Flathead does nothing of value before about 4000 - 4500 RPM . . . actually it hurts low end power as it reduced compression (with everything else the same). Also, relieving is just one small piece of the overall puzzle - you have the ports to worry about (they take serious amounts of work), you have the cam to worry about, you have the valves, the chambers in the heads, etc.. As Pete noted - when all the things are specifically designed to work together (for racing) - then relieving is part of the "combo" that was typically used.

Also, typically these naturally aspirated engines were fuel injected - which surely adds horsepower over the typical Stromberg setup. And truth be told, the classical Hilborn flathead injector is too small for max HP. Guys like Don Ferguson Sr. cast their own injectors way back in the 80's - with big port/butterfly sizes more like a SBC injector (to get the flow they needed).

Then, one can start talking about oil-control, dry-sumps, crank scrapers, vacuum pumps, low-tension rings, straight-cut cam gears, etc.. A lot can go into one of these engines - and it is not for those "on the cheap".

Dale, Thanks for a very balanced and informative discussion of the topic!.
John

[Pete]

Originally Posted by Jack E/NJ

RR>>Here's one of them Ford flathead speed secrets learned some time ago a built not relived Ford flathead will rev to 5 grand. To get another thousand RPM a relief will get you there.>>>


Interesting. I'd hafta guess that the Hudson racing cognoscenti had a few secrets like this as well.

You are right there. I learned a lot from Smokey.

[Bored&Stroked]

Originally Posted by John R

Dale, Thanks for a very balanced and informative discussion of the topic!.
John

This has been a good thread - based on a lot of the folks contributing who have many years of experience with these goofy engines (not only Ford, but many other variants).

Like anything else, there is no one "right" answer . . . the answer is the usual "well, it depends".

[Zeke3]

I am not sure exactly how the rating system works on this forum, but if you have enjoyed this discussion I encourage you to rate this thread. The “Rate this thread” button is in the ribbon at the top of the thread. Normally I would rarely rate a thread, but there are special discussions that warrant a rating.

I have thoroughly enjoyed this discussion. Thanks to Ol Ron for kicking off this thread.

[Ol' Ron]

Well over 1400 people have looked at it so I guess you can take your pick RR , I appreciate your input, what you've done to improve the flathead in competition is impressive. What I learned from limited stock car racing has allot to do with my building knowledge. Right now I working on a street engine with Good performance, good economy, long life and under 3K$. That might be harder than running at Bivll.
Gramps

[Tim Ayers]

Originally Posted by Graeme / New Zealand

I have a 99A block sitting under a tarp that is factory relieved.

GB

To add to this, I have three 99A's. Two are relieved and one is not. I'd assume the two that are were in trucks. One of the relieved and the non-relieved are both crack in the #3 intake valve seat.

[38 coupe]

Is this a decent summary of the information in this thread?


1 - Below 4500 rpm there is no benefit to a relief.

2 - For motors built for competition use a relief can help, but must be carefully designed. The rpm range of competition will heavily favor whether a relief is helpful or not.

3 - For all out high rpm use such as land speed racing a relief is necessary.

[Tim Ayers]

Originally Posted by 38 coupe

Is this a decent summary of the information in this thread?


1 - Below 4500 rpm there is no benefit to a relief.

2 - For motors built for competition use a relief can help, but must be carefully designed. The rpm range of competition will heavily favor whether a relief is helpful or not.

3 - For all out high rpm use such as land speed racing a relief is necessary.

Thanks all for contributing to this thread.

[itslow]

Originally Posted by V8COOPMAN

...I've still gotta ask WHY did those Frenchmen go to the trouble on those beautiful French flatheads (one of which I just sold the last couple of days), as well as the relatively few that Henry Ford produced for buses and other industrial equipment?

Truck and industrial engines which see high load over extended periods of time will often have lower compression ratios. One way of doing this is to relieve the block. GM did this on the 348-409 Chevrolet truck and industrial engines. I'd suspect Ford did the same.

[Pete]

Originally Posted by 38 coupe

Is this a decent summary of the information in this thread?
1 - Below 4500 rpm there is no benefit to a relief.

2 - For motors built for competition use a relief can help, but must be carefully designed. The rpm range of competition will heavily favor whether a relief is helpful or not.

3 - For all out high rpm use such as land speed racing a relief is necessary.

1 - "Below 4500 rpm there is no benefit to a relief."
Wrong.

2 - "For motors built for competition use a relief can help, but must be carefully
designed.
You will be in the "C" main without it and there is no design to it. You just
go bigger.

"The rpm range of competition will heavily favor whether a relief is helpful
or not".
It helps over the whole rpm range.

3 - "For all out high rpm use such as land speed racing a relief is necessary."
Right.

[Ronnieroadster]

Originally Posted by 38 coupe

Is this a decent summary of the information in this thread?


1 - Below 4500 rpm there is no benefit to a relief.

2 - For motors built for competition use a relief can help, but must be carefully designed. The rpm range of competition will heavily favor whether a relief is helpful or not.

3 - For all out high rpm use such as land speed racing a relief is necessary.

My thoughts are what Pete said.
Ronnieroadster

[Jack E/NJ]

Pete >>> 1 - "Below 4500 rpm there is no benefit to a relief." Wrong.>>>


Maybe this is a companion question that should be kept in this thread.

Since most of us seem to have unrelieved blocks --- and since block relieving seems so drastic especially if something goes wrong --- should I somehow relieve my head instead?

Well, sorta. Fill in most of the dead zone over the hole? Examples below from a hamb thread. I can almost see the swirlies happen as the mixture gets sucked into the hole.


https://www.jalopyjournal.com/forum/...-head.1242895/

















.

[Bored&Stroked]

The question comes back to the application and usage of the engine. In a performance built engine, a relief will help - especially if you have good port/valve work done, cam, heads, etc.. In a stocker type engine, it will reduce compression and there is not a huge amount of benefit. Also, what RPM do stock engines usually run at?

Pete, Ron and I probably relieve every engine we build - as we do not build stock type engines. I've not built a stock engine in 40 years.

If I was building a stocker or mild performance type engine, I'd probably do more of a blend of the transfer areas around the valves - more of a 1/2 relief to improve flow out of the valve pocket. Also, consider that stock type engines are already suffering from low compression - do you want it any lower?

Here are a few pictures of what I'll call a 1/2 relief - it was done for a 276 cubic inch street engine running dual carbs and a Potvin 3/8 cam. Stock valves sizes, street porting and guide work (on the tops). This is kind of a "tweener" - improved ports, a 1/2 relief - not a competition style engine, but surely an improvement over stock. It ran extremely well in a street driven Model A roadster:

PortsFinished1 copy.jpg

ReliefWithRadiusBoreEdge copy.jpg

GuideInPort1.jpg

[Tim Ayers]

Originally Posted by Bored&Stroked

The question comes back to the application and usage of the engine. In a performance built engine, a relief will help - especially if you have good port/valve work done, cam, heads, etc.. In a stocker type engine, it will reduce compression and there is not a huge amount of benefit. Also, what RPM do stock engines usually run at?

Pete, Ron and I probably relieve every engine we build - as we do not build stock type engines. I've not built a stock engine in 40 years.

If I was building a stocker or mild performance type engine, I'd probably do more of a blend of the transfer areas around the valves - more of a 1/2 relief to improve flow out of the valve pocket. Also, consider that stock type engines are already suffering from low compression - do you want it any lower?

Here are a few pictures of what I'll call a 1/2 relief - it was done for a 276 cubic inch street engine running dual carbs and a Potvin 3/8 cam. Stock valves sizes, street porting and guide work (on the tops). This is kind of a "tweener" - improved ports, a 1/2 relief - not a competition style engine, but surely an improvement over stock. It ran extremely well in a street driven Model A roadster:

Attachment 531548

Attachment 531549

Attachment 531550

Dale,

Looks great, as usual. This is close to the type of relief that Barney Navarro used on his engines.

I've curious about the "eyebrow" above and 1/2 way between the valves. Any thoughts on if this metal impedes, improves or is indifferent to flow?

Jack E/NJ,

Thanks for posting the heads picts. Curious about head combustion chamber shape and how to improve that area as well.

[Pete]

If you are going to modify your engine to ANY degree, you must understand the basics of what works as "stand alone mods" and grouped mods.

Stand alone mods are things that improve performance by themselves, such as a computer type ignition.
More compression.
More cubic inches.
More flow exhaust.

Any one of these by itself will improve performance.

Grouped mods are any combination of the above including a performance camshaft, big valves, dry sump, port work, relief, modified heads and many other things.

You DO NOT relieve a block and not do something to raise the compression back to at least where you started.
That is like having a bad set of spark plugs and only replacing half of them.

[Pete]

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Originally Posted by Jack E/NJ

I can almost see the swirlies happen as the mixture gets sucked into the hole.

The mixture is not sucked in. It is forced in by atmospheric pressure. The intake vacuum does enhance the flow though.

Pressure and vacuum flow systems behave differently.

[Bored&Stroked]

Originally Posted by Pete

If you are going to modify your engine to ANY degree, you must understand the basics of what works as "stand alone mods" and grouped mods.

Stand alone mods are things that improve performance by themselves, such as a computer type ignition.
More compression.
More cubic inches.
More flow exhaust.

Any one of these by itself will improve performance.

Grouped mods are any combination of the above including a performance camshaft, big valves, dry sump, port work, relief, modified heads and many other things.

You DO NOT relieve a block and not do something to raise the compression back to at least where you started.
That is like having a bad set of spark plugs and only replacing half of them.

Very well said Pete! I like the way you elaborated on "grouped mods" - which was what I was trying to convey in my earlier posts.

[Jack E/NJ]

TA>>>Curious about head combustion chamber shape and how to improve that area as well.>>>

Yeah, me too. While a better-designed slug crown seems like it might help fill the compression void, reducing the dead zone as in Hudson's vortex head might be the next best thing?

[Pete]

I always welcome data on twiddle diddling with any engine component that will make the dyno reading go higher.
Even if it is only 1 or 2 hp.
I had a friend in the 50's that was a Boeing engineer and owned a Kurtis 3000 series Indy car.
As a side project once in awhile he would help us with race car math problems that were more easily solved on the Boeing analog computer rather than with a slide rule.
He and I both met Smokey Yunick at a race we went to watch once. Smokey was running Hudsons at the time. From a short talk after the race we were able to get enough info to reverse engineer what he was doing with the Hudson combustion chamber which was similar to what we had been doing to the Ford's except on a bigger scale. We went bigger on the relief and went faster.
Little humps and pathways in either the block or heads never worked for us.

[Ronnieroadster]

Pete its been my experience the more I opened up the combustion chamber in the head and the relief as well we continued to make more power. No humps or pathways needed as far as I have determined.
Ronnieroadster

[jplutz]

Jack, why are there holes directly over the piston in the Rocket head?

[cadillac512]

Those are just casting divots. Some Ford heads have them too, in varying size and depth.

[Bored&Stroked]

Originally Posted by Ronnieroadster

Pete its been my experience the more I opened up the combustion chamber in the head and the relief as well we continued to make more power. No humps or pathways needed as far as I have determined.
Ronnieroadster

Generally, I'd agree - though when you're running a supercharger/blower or any forced induction, it is a different beast than a NA situation. The quest is how to increase flow and also maintain or increase compression.

If you look at the Harley KR's, they were ALL about flow and compression was not the bigger issue. BUT they had huge duration/overlap in their cams, tight lobe centers, fantastic ports, huge valves and very specifically designed chambers. They were also very high RPM flatheads - they spun them at 8,000 rpm all the time, so low-end power was really not the issue . . . higher RPM horsepower (which means flow) was the issue.

One thing I believe in as it relates to the Harley KR design is the flow-ramp across the cylinder. If you look at the pictures I've posted, the flow comes across from the intake to the bore. I suspect this is a very important aspect of the design - and resulting performance.

The intake charge had a very easy path down the cylinder (and it swirled the charge) and the bore was not covered up by the head chamber. Also, as the design used a pop-up, the chamber was "out of the way" of the flow once the piston was 3/16" down the bore.

The pop-up opened up the opportunity for flow, without sacrificing compression. To me, this is the beauty of the design. This is exactly what I did in the FlatCAD design - following the specific design notes of Jerry Branch with his Harley KR mods.

Another thing I've done is to put a heavy radius on the leading edge of the pistons for two reasons. 1) to reduce the tendency for the edge to overheat. 2) It helps flow get over the top of the piston as the piston starts to move down the bore. Here is what the pistons/deck look like presently - as I'm currently getting the engine ready for Bonneville (flathead Cadillac):

IMG_0076.jpg

69307476044__EA44891C-31EC-4D17-B161-C71AAB3869D1.jpg


For those who are interested, do some searches for the articles that Jerry Branch published on modifications to the Harley KR (back in the 60's).

[petehoovie]

Originally Posted by Bored&Stroked

Generally, I'd agree - though when you're running a supercharger/blower or any forced induction, it is a different beast than a NA situation. The quest is how to increase flow and also maintain or increase compression.

If you look at the Harley KR's, they were ALL about flow and compression was not the bigger issue. BUT they had huge duration/overlap in their cams, tight lobe centers, fantastic ports, huge valves and very specifically designed chambers. They were also very high RPM flatheads - they spun them at 8,000 rpm all the time, so low-end power was really not the issue . . . higher RPM horsepower (which means flow) was the issue.

One thing I believe in as it relates to the Harley KR design is the flow-ramp across the cylinder. If you look at the pictures I've posted, the flow comes across from the intake to the bore. I suspect this is a very important aspect of the design - and resulting performance.

The intake charge had a very easy path down the cylinder (and it swirled the charge) and the bore was not covered up by the head chamber. Also, as the design used a pop-up, the chamber was "out of the way" of the flow once the piston was 3/16" down the bore.

The pop-up opened up the opportunity for flow, without sacrificing compression. To me, this is the beauty of the design. This is exactly what I did in the FlatCAD design - following the specific design notes of Jerry Branch with his Harley KR mods.

Another thing I've done is to put a heavy radius on the leading edge of the pistons for two reasons. 1) to reduce the tendency for the edge to overheat. 2) It helps flow get over the top of the piston as the piston starts to move down the bore. Here is what the pistons/deck look like presently - as I'm currently getting the engine ready for Bonneville (flathead Cadillac):

Attachment 531719

Attachment 531720


For those who are interested, do some searches for the articles that Jerry Branch published on modifications to the Harley KR (back in the 60's).

[tippa77]

This is very interesting !

[Jack E/NJ]

B&S>>>The intake charge had a very easy path down the cylinder (and it swirled the charge) and the bore was not covered up by the head chamber. Also, as the design used a pop-up, the chamber was "out of the way" of the flow once the piston was 3/16" down the bore.>>>


Yes. Very interesting indeed! Could we perhaps get a better side view of the crown profile please?

[Bored&Stroked]

The pistons are in the engine - so this is the best I can do. They are flat-top, with a .040 squish to the head, the radius is done by hand and then I balance the pistons to the same gram weight. The radius on the leading edge follows the shape of the relief - a bit of an angle (notice that it is clocked off of straight up - four pistons go one way, four go the other way.

Also, keep in mind the level of porting in this block (extreme) and the port sizes are a whole lot bigger than a Ford. Both intakes and exhausts exit out the top - the exhausts don't "snake" through the block like on a Ford. All in all, a much better flowing design (and bigger cubes) than a Ford. BUT - not easy to design, build and work on.

I moved the ring pack down for this iteration of the piston design (as it is blown and under quite a bit of boost) - we're running metric rings (which is all I run if I have a chance).

IMG_0004.jpg

IMG_0005.jpg

IMG_0039.jpg

IMG_0040.jpg

[Jack E/NJ]

Thanks! What are those speckles that seem to be on the seats? Pits?

[jplutz]

B&S, The polished ports are beautiful, like jewlry. I had a 40 LaSalle coupe' in high school. It sounded great with straight pipes! My dad would chew me out when the old bat across the street called to complain at supper time! I had a cable cut-out����! JPL

[cadillac512]

Originally Posted by Jack E/NJ

Thanks! What are those speckles that seem to be on the seats? Pits?

Pretty sure these pics were taken before the final finishing of the seats was done,hence the pits. Beautiful work!

[Ronnieroadster]

Dale
While its true I do spend most of my energy running a supercharger which would for the most part not be effected greatly by lower compression created by the relief.

BUT here's some testing results from two test runs that took place in July with our car taken without running the supercharger. Here's the details with the supercharger removed I replaced it with a hand made intake I'm experimenting with that has two Holley two barrel carbs set on top. The engine is the same 292 cubes we run burning VP 116 octane racing gas the car as I wrote earlier is over 3000 pounds. The first test run I held the RPM to 5000.
From a standing start at the measured timed 1 mile the speed was over 130 MPH at the 1.5 timed mile mark the speed was over 140 MPH.

Upon checking date I decided to add two more degrees of timing now 23 all in and actually go bigger on the jetting. For this second run the RPM was increased to 6000. The speed attained at the 1 mile mark was now 143 MPH and at the 1.5 mile mark 153 MPH. The second run speed is more than 10 MPH faster than the current record at Bonneville set by an engine that measured well over 300 cubes. There's a lot more left in our new normally aspirated gas combination I'm certainly looking forward to more testing on our stock block Ford flathead.
Ronnieroadster

[Bored&Stroked]

Originally Posted by Jack E/NJ

Thanks! What are those speckles that seem to be on the seats? Pits?

The ports were touched up before the valve job was applied - this was pre-valve seat work.

[Bored&Stroked]

Originally Posted by Ronnieroadster

Dale
While its true I do spend most of my energy running a supercharger which would for the most part not be effected greatly by lower compression created by the relief.

Ronnieroadster

I agree with you Ronnie - I would ALWAYS be running a 3/16" deep or so relief on a racing style engine or really any decently performance modified engine (like everything you and I build). What is important for folks to understand is that in our applications the HP we pick up by increased flow more than offsets any compression ratio losses. Flow is everything for all racing engines - flatheads included.

It is the same reason one can buy a set of out-of-the-box AFR 195 heads for a SBC, stroke it a bit and make over 500 HP with a hydraulic street cam and a single 4 barrel. It is the top-end technology (and cams) that have made the biggest differences in horsepower gains for our classic OHV engines.

On the other hand, having high compression but lack of flow might work at low RPMs on the street, but it will never make HP at higher RPMs and one might not even get to higher RPMs.

We're on the same page . . . as usual!

[Pete]

...

[petehoovie]

Originally Posted by Pete

...

[38 coupe]

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At the other end of the spectrum I'm confident not relieving the block on a "stock" rebuild. For my use I'm looking to maximize low end torque not horsepower. With overdrive I don't need or want higher rpm capability, I want maximum torque below 3000 rpm. I use stock intakes, distributors, and camshafts. I was very impressed with the drive-ability of the motor I helped my friend build for his family's 1950 Mercury: .060 over 8BA block (we would have bored smaller but it took that to clean up), 4 inch crank, EAB cam, stock heads shaved to get .040 above the pistons (EAB heads probably would have been more torque, but we stuck with the Mercury marked heads), stock carburetor and distributor, no port work. The car owns overdrive at 80 mph with the engine spinning less than 2900 rpm.

[Bored&Stroked]

Originally Posted by petehoovie

Now Pete . . . show us the "AFTER" view of the chambers!

[cadillac512]

Originally Posted by 38 coupe

At the other end of the spectrum I'm confident not relieving the block on a "stock" rebuild. For my use I'm looking to maximize low end torque not horsepower. With overdrive I don't need or want higher rpm capability, I want maximum torque below 3000 rpm. I use stock intakes, distributors, and camshafts. I was very impressed with the drive-ability of the motor I helped my friend build for his family's 1950 Mercury: .060 over 8BA block (we would have bored smaller but it took that to clean up), 4 inch crank, EAB cam, stock heads shaved to get .040 above the pistons (EAB heads probably would have been more torque, but we stuck with the Mercury marked heads), stock carburetor and distributor, no port work. The car owns overdrive at 80 mph with the engine spinning less than 2900 rpm.

Very close to what I'm running in the '41 Merc. 8CM cam and EAB heads, but 2G Rochester and Chev distributor. Great power low and mid range, perfect for the application.

Agree with the serious performance guys here though...it's all about air flow when things get serious. Cool stuff!

[38 coupe]

Originally Posted by Bored&Stroked

Now Pete . . . show us the "AFTER" view of the chambers!

You know serious performance work is happening when someone welds up the chambers on brand new heads.

[Ol' Ron]

Somewhere in my past I missed this improved relief In the 60's and earler I relieved all my engines, but I wasn't in organized track racing, just street drags and a trip to Oarange to dragrace among the sky divers. Early track engines were relieved, but after a few years I discovered most builders stopped that. MY first trip to Bville was also interesting, Most of the blocks I saw there didn't have reliefs either NOT havinf FACTFUL information. I stopped relieving bocks and suggested to others that it didn't improve power and economy. I feel better now, however I've also made some port improvements that I don't think many people have done and have tried to post them on the barn these past few day with no luck. Very high STUPID factor here. I have some help coming over tomorrow and that might solve the problem
I have literly hundreds of pics of my experimenting back when I had my dyno, Most of the engines I built for coustomers were run on it for grakin and to prove the output. Non of them mad much HP but allot of torqur,
Gramps

[38 coupe]

Ron,
I would be very interested in what modifications you found to improve low end torque. Your book and JWL's book go into low end torque, but none of the other flathead books really cover the subject. Flathead engine books almost always are about making top end horsepower numbers and/or looking modified with lots of polished aluminum parts.
At this point my limited understanding is maximizing low end torque is all about more displacement (longer stroke since I want to keep the cylinder walls thick), higher compression, and a stock camshaft. With a stock intake and carburetor do you think there is any benefit to any port modifications?

[Jack E/NJ]

B&S>>>Now Pete . . . show us the "AFTER" view of the chambers!>>>


38C>>>You know serious performance work is happening when someone welds up the chambers on brand new heads.>>>


Aye!!! Even I couldn't bring myself to do this. I however might be tempted to attach a plate and use a form-working hammer to do something similar ---- but reversible.

[Bored&Stroked]

This is what you do when you want custom chambers - most likely with flat top pistons!

[Jack E/NJ]

I guess when they're milled flat,.they won't look so much like cowpies.

[old Tom]

JWL covered this in his book however he said that on A full rave block relieving did help tom Beaty, The Beean bandits, John Bradly, art Christian etc. all ran fast FH.s they all relieved their blocks. They couldn't all have been wrong...

[Pete]

Originally Posted by Bored&Stroked

Now Pete . . . show us the "AFTER" view of the chambers!

I don't have any pics of that but just imagine a completely flat surface for flat top pistons.
The slight kickout in the chamber on one side is straightened to get maximum area available. Edelbrock heads do not have this kickout so they are a bit easier to do.
Sometimes the transfer area is welded back to the edge of the valve. This is the area that is machined to adjust the compression.

[Bored&Stroked]

Hey Pete, have you ever tried any type of flat-top popup piston? Would seem that you'll still get the compression, but open up the roof of the chamber? Obviously, this is what Harley did with the KR - about a 3/16" pop-up. This is what I did with the FlatCad - to mimic the Harley. BUT, I've never had the luxury of time, money and a dyno to try different combinations.

I'd love to have a 1-cylinder engine with a flathead port, head, chamber setup - to test all sorts of things on a motorcycle dyno! LOL

Or maybe cutup a block and make a V-Twin flathead for testing.

[Tim Ayers]

Originally Posted by Bored&Stroked

Hey Pete, have you ever tried any type of flat-top popup piston? Would seem that you'll still get the compression, but open up the roof of the chamber? Obviously, this is what Harley did with the KR - about a 3/16" pop-up. This is what I did with the FlatCad - to mimic the Harley. BUT, I've never had the luxury of time, money and a dyno to try different combinations.

I'd love to have a 1-cylinder engine with a flathead port, head, chamber setup - to test all sorts of things on a motorcycle dyno! LOL

Or maybe cutup a block and make a V-Twin flathead for testing.

Dale,

I often think about doing this with a single cylinder Briggs & Stratton motors that can be had pretty cheaply. I've also thought about bench grinding the cam as well just to fool around with some ideas.

Any know how closely related a B&S flathead is to a Ford?

Tim

[flatjack9]

When I was an engineer at IH in the 60's and 70's, we had a single cylinder engine built for combustion chamber studies. As I remember, it had about a 250 lb flywheel. Once a rocker stud broke during a test and it took about 5 minutes before the engine stopped.

[Pete]

Originally Posted by Bored&Stroked

Hey Pete, have you ever tried any type of flat-top popup piston?

No. When you are trying to get maximum compression, why do something that
decreases compression.Two flat mating surfaces are the minimum area attainable.
Also, the flame front travels faster over a flat surface rather than one with
humps, valleys and corners..

[Jack E/NJ]

Maybe B&S meant with a corresponding flat recess up into the head too?

[Tim Ayers]

Originally Posted by Pete

No. When you are trying to get maximum compression, why do something that
decreases compression.Two flat mating surfaces are the minimum area attainable.
Also, the flame front travels faster over a flat surface rather than one with
humps, valleys and corners..

So to confirm what you are saying, Pete. Your thoughts on an ideal chamber is a flattop piston that does not extend past the deck surface and a corresponding flat chamber in the head?

[Pete]

Originally Posted by Tim Ayers

So to confirm what you are saying, Pete. Your thoughts on an ideal chamber is a flattop piston that does not extend past the deck surface and a corresponding flat chamber in the head?

Yes.

[Ol' Ron]

I can understand why relieving the block works do well. most of the cylinder heads have very little transfer area so relieving is there to make up the difference. I was just looking at my Hydro engines, They rak well over 5K and when they came out of the water Pegged the needle, Somebody here suggested Monkey see, monkey do, Yes, I can see how it might work My Grancore heads used apopu piston In my Bvill engine I used 3 3/4 stroke pistons on a 4" crank

[Jack E/NJ]

Pete >>>When you are trying to get maximum compression, why do something that
decreases compression.>>>


I'm confused. How does a flat popup that kisses a correponding flat recess reduce compression?

[Bored&Stroked]

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Originally Posted by Jack E/NJ

Pete >>>When you are trying to get maximum compression, why do something that
decreases compression.>>>


I'm confused. How does a flat popup that kisses a correponding flat recess reduce compression?

It shouldn't as long as the squish is the same. There would be a tiny bit of loss around the perimeter of the pop-up - as it obviously can't scrape the chamber. You can see on my piston design for the FlatCAD, I have a tiny "relief" in the area of the pop-up.

[Pete]

Originally Posted by Jack E/NJ

Pete >>>When you are trying to get maximum compression, why do something that
decreases compression.>>>


I'm confused. How does a flat popup that kisses a correponding flat recess reduce compression?

I guess things got jumbled in the interpretation somewhere.
Two flat surfaces mating will have the smallest area between when brought together.
Add a dome or pop up and you INCREASE area and reduce compression.

[Tim Ayers]

Pete,

How much "squish" do you aim for when you run the flattop set-up?

Tim

[Bored&Stroked]

Originally Posted by Tim Ayers

Pete,

How much "squish" do you aim for when you run the flattop set-up?

Tim

On the FlatCAD, I always tune the squish for .040. If your bores are good and you don't have excessive clearance, then piston rock is at a minimum and you might get away with as low as .030. Also, depending on whether you're running NA or boosted, this can certainly come into play.

[Pete]

Originally Posted by tim ayers

pete,

how much "squish" do you aim for when you run the flattop set-up?

Tim

.035

[Jack E/NJ]

B&S>>>shouldn't as long as the squish is the same. There would be a tiny bit of loss around the perimeter of the pop-up - as it obviously can't scrape the chamber.>>>


Pete>>>Two flat surfaces mating will have the smallest area>>>


OK. Thanks. Makes sense.


Another thing. Smooth arching reliefs into the heads seem like they would be better for flow drag reduction than 90 degree reliefs in the deck. Even though a bit of turbulent mixing might be lost, charge might be greater?

[Ol' Ron]

I don't think the charge over the piston is immportant. It should be in the combustion chamber with the spark plug.
Gramps

[Jack E/NJ]

Well yeah at ignition time. But first gotta fill the hole with as much charge as possible before ignition happens.

[Bored&Stroked]

One also had to think about flame travel and in the end, the charge has to force the piston down - so how the flame travels and if it travels toward the back of the piston top does come into play. Some of the more modern CFD software packages can do simulations that are pretty dang good as they relate to cylinders and combustion chambers and the various cycles of an IC engine.

[Jack E/NJ]

No CFD simulation needed for watching a flame-front travel in an early Ford glasshead v8. Gotta blink fast though. Or may be use a high speed camera. Interesting how the flame looks hotter down the hole than in the combustion chamber.


https://www.youtube.com/watch?v=-PYaJW_jQW4

[Bored&Stroked]

As this is the "Mother of all Threads" on the subject of reliefs. Here is a "stepped" relief that I did on my own "experimental" 284 cubic inch engine that is in my 32 Cabriolet.

I did this to mimic some of the Harkey KR race jugs that I happen to have. I've used this engine to try some different ideas, concepts and parts out on.

It has a big-ass roller cam (huge duration and .420 lift), coatings on pistons, valves, cometic MLS head gaskets, etc..

A guy needs to have a flathead "playground" to have some fun in. LOL

SteppedRelief1.jpg

DeckComplete.jpg

[petehoovie]

Originally Posted by Bored&Stroked

As this is the "Mother of all Threads" on the subject of reliefs. Here is a "stepped" relief that I did on my own "experimental" 284 cubic inch engine that is in my 32 Cabriolet.

I did this to mimic some of the Harkey KR race jugs that I happen to have. I've used this engine to try some different ideas, concepts and parts out on.

It has a big-ass roller cam (huge duration and .420 lift), coatings on pistons, valves, cometic MLS head gaskets, etc..

A guy needs to have a flathead "playground" to have some fun in. LOL

Attachment 531943

Attachment 531944

[Pete]

You give up a LOT of intake port area with those old raised surface blocks.

I have never heard of anyone machining the raised surface off before porting. Have you??

[Bored&Stroked]

Originally Posted by Pete

You give up a LOT of intake port area with those old raised surface blocks.

I have never heard of anyone machining the raised surface off before porting. Have you??

Hey Pete - I have not either, but I can't see there being an issue doing so. What I have not tested (with a sonic tester) is there any difference in the amount of material below the raised intake surface? Interesting thing to ponder!

[Pete]

Originally Posted by Bored&Stroked

Hey Pete - I have not either, but I can't see there being an issue doing so. What I have not tested (with a sonic tester) is there any difference in the amount of material below the raised intake surface? Interesting thing to ponder!

I have never owned one of those blocks so no test data available.

[Jack E/NJ]

Pete>>>You give up a LOT of intake port area with those old raised surface blocks.>>>


A LOT? How much? Not much of a ridge. What was it's purpose anyway? Easier to re-surface if needed?

[Tim Ayers]

Now I'm curious. From what I gather, it's not so much higher, but the surface below it is lower. I have a few in the garage and now I feel the need to do some measuring.

[Bored&Stroked]

I think Pete's point is that when doing extremely large full-competition porting (like bigger 'D' ports toward the cylinders), you'll run out of material toward the outside edge of the raised intake area. On later 59x or 8BA blocks the whole surface is flat, so you can be more aggressive and not have a sealing issue.

[Jack E/NJ]

TA>>>it's not so much higher, but the surface below it is lower>>>
B&S>>> On later 59x or 8BA blocks the whole surface is flat, so you can be more aggressive and not have a sealing issue.>>


OK, Makes sense. But why do you suppose the surface was ever milled down that way to make a ridge in the first place? My '38 21-studder doesn't have a ridge either.

[Bored&Stroked]

Originally Posted by Jack E/NJ

TA>>>it's not so much higher, but the surface below it is lower>>>
B&S>>> On later 59x or 8BA blocks the whole surface is flat, so you can be more aggressive and not have a sealing issue.>>


OK, Makes sense. But why do you suppose the surface was ever milled down that way to make a ridge in the first place? My '38 21-studder doesn't have a ridge either.

I've heard various claims - and they are probably all bogus. The most popular one was that "Henry wanted to save a few pennies on the overall cost of cast iron." If that was the case, then why did they go back to the older method in most of the 59x blocks and every 49-53 block that I've had?

My guess is that they made their patterns a few different ways and later decided to go back to a "flat top". Who knows the truth . . .

[Ronnieroadster]

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Hi guys I have had my hands involved in a lot of those so called raised deck blocks. From what I can tell while area for the intake surface appears to be raised the ports are not any higher than a conventual block. This visual appearance on the block between outer edges of the ports to the top edge of the decks are actually just lower than the typical flathead block casting. These blocks are called the 39 Mercury block if the bore is 3 -3/16 however I have seen the same casting with a bore of 3-1/16. Maybe at the time the thought was a little less iron would be used for the casting process thus a cost savings.
The only disadvantage I can see is the difficulty in making the top intake port the D shape other than that they are a cool looking block.
Ronnieroadster

[Bored&Stroked]

Ronnie is correct, they made the raised intake surface blocks in both 221 cubic inch Ford sizes as well as the 239 cubic inch Merc, Truck and WWII production versions.

Another term for them was the 'Keystone" block -- with many tall tales about how they were thicker, had more nickel content, made hair grow on bald heads, that all the "chicks dig them" . . . you get the point . . . lots of urban myths!

I've done quite a bit of analysis; I've managed to corroborate none of the myths - especially the last one mentioned above.

[Jack E/NJ]

I guess if the blocks were actually cast --- instead of milled --- that way, you might save a few milling pennies too?.

[Bored&Stroked]

Originally Posted by Jack E/NJ

I guess if the blocks were actually cast --- instead of milled --- that way, you might save a few milling pennies too?.

They were not milled - this was all due to the casting patterns they used. Why? Who knows . . .

[Pete]

Originally Posted by Jack E/NJ

Pete>>>You give up a LOT of intake port area with those old raised surface blocks.>>>

A LOT? How much? Not much of a ridge. What was it's purpose anyway? Easier to re-surface if needed?

Here is a size comparison of a rough finish port to a stock one.. There is about .030 more to finish size.

[petehoovie]

Originally Posted by Pete

Here is a size comparison of a rough finish port to a stock one.. There is about .030 more to finish size.

[Tim Ayers]

Originally Posted by Ol' Ron

I can understand why relieving the block works do well. most of the cylinder heads have very little transfer area so relieving is there to make up the difference. I was just looking at my Hydro engines, They rak well over 5K and when they came out of the water Pegged the needle, Somebody here suggested Monkey see, monkey do, Yes, I can see how it might work My Grancore heads used apopu piston In my Bvill engine I used 3 3/4 stroke pistons on a 4" crank

Originally Posted by Pete

Here is a size comparison of a rough finish port to a stock one.. There is about .030 more to finish size.

Pete,

I understand what you mean now. Issues with the a large D port not sealing on raised intake block due to the lack of material would be the "lowered" section in the direction towards the deck surface. Never thought of it that way, but I guess you are right.

Regarding D shaped ports, do you guys do this on a mill or freehand? If freehand, any useful tips or tricks?

[Pete]

Originally Posted by Tim Ayers

Pete, Regarding D shaped ports, do you guys do this on a mill or freehand? If freehand, any useful tips or tricks?

We do it by hand with a air die grinder and carbide burrs.
We researched doing it with CNC but what with only doing one every few years, it was not worth the effort.

[Jack E/NJ]

B&S>>They were not milled - this was all due to the casting patterns they used. Why? Who knows>>>


What I meant was only the raised area would need to be milled for a good seal, not the whole top. So less milling costs.

[Jack E/NJ]

Pete >>>We do it by hand with a air die grinder and carbide burrs.>>>


If the cylindrical area defined by an open valve and its seat is probably always gonna considerably smaller than the port area, then how much do you really gain by further enlarging the port area?

[Pete]

Originally Posted by Jack E/NJ

Pete >>>We do it by hand with a air die grinder and carbide burrs.>>>


If the cylindrical area defined by an open valve and its seat is probably always gonna considerably smaller than the port area, then how much do you really gain by further enlarging the port area?

A simple analogy might be a river. You gain more usable pressure by damming it rather than having it free flow.
The valve seat is the dam, the port behind it is the lake.
The more surface area in the lake the higher the pressure at the outflow due to atmospheric effect and dead weight of the water. (fuel charge dead weight plus inertia)
How much gain?? If we get to the finish line 1 inch ahead of the next car, we win.

[Jack E/NJ]

I guess I looked at it more like two funnels or cones having the same minor exit orifice surface areas, same column lengths or heads, but different major entrance orifice surface areas. Flow rates should be about the same due to the same heads at the same minor diameter orifices despite the volume differences

[Bored&Stroked]

I think the way to look at it is the amount of stacked up intake charge (fuel, air and pressure) that the bigger port has on the flow equation.

It is like having your finger over the end of a hose, the more pressure in the hose when you first let your finger off, the bigger the initial "burst" out of the hose end. That is about the best analogy I can come up with . . . after a good bourbon cocktail! LOL

[Jack E/NJ]

Lotsa variables & combinations thereof!

[Ol' Ron]

The biggest problem with FLOW is turbulence. My new port will be Linier very little curvs. Like the wings of an airplane. skin friction causes turbulence.
Everybody has their ideas. What somebody did last year, just improves what somebody does this year,
Graps

[Ol' Ron]

I've tried to post a few oics today, BUT, my stupid factor is too high and nothing seems to work. Directions are simols ------- select===== upload=== and it there. Much too complicated for me'G