Building for Torque Porting Question

[Scotty's 52 F3]

I'm getting ready to pull my 52 F3 down for body and paint as well as engine build. I'm gathering parts and got hold of a Merc crank, EAB cam and EAB heads. I'd like to run 3 ring pistons with a more modern ring pack. The only cast versions I see is EGGE in .125 over which I may do if the block will handle it. I don't mind spending the money on Ross pistons if they are less trouble with domes vs heads. I have a 49 block and my still running 52. I'll use whichever is best. I'm already running a modified Accel dual point with a vacuum advance and advance curve as recommended by JWL a while back for my stock 8RT engine. My engine runs well considering all the blow-by it has.

I have JWL's book as a guide so I was also considering an Offenhauser 4 bbl. intake with the 465 Holley. My exhaust manifolds are cracked so I was going to fabricate some center dump type headers and run through some 1 3/4" duals. I have more time than money so I fab as much as I can. Part of the fun anyway.

My question is about porting.......or not, for this build. Do I need to do more than gasket match, blend bowls and radius the sharp edges? If so, does anybody have some specific info or pics for an engine being built for low RPM torque? Would a center port divider benefit me in this case? Any build advice would be greatly appreciated.

[flatheadmurre]

For a F3 with EAB cam and aiming for torque and not more revs i would say compression is what you want instead of large ports.
If you use it for hauling running it hard the higher compression can be an issue...so depends on what you want it to do.
Cleaning up the intake and exhaust ports never hurts...but any serious porting isn´t what you need in my opinion.

[drolston]

Looks like you will end up with 270 or so cubic inches. The 390 CFM Holly might be better suited than the 465. Relieving the area between the valves and cylinder is worth the time and effort. Porting the intakes is much less return on time and effort, but you can get some of that type benefit from cut down valve guides and power-flo valves.

The EAB cam is good for low-end torque; other than that, it is cubic inches, especially from stroke.

I have no personal experience, but the consensus on this board has been that center port dividers do not benefit performance.

[Kahuna]

IMO
Make the engine as large as you can.
Balance the engine
Ross pistons with the metric ring pack are excellent
Do the mild cleaning up of the ports
Do not waste your time relieving the engine
I believe the Offy manifold has the fan mount offset. May be a a consideration.
Maybe the Edelbrock is a better option
Get a cam, maybe the L100 from Krylon. It'll work well
Raise the compression at least 8:1. More if possible
You'll have a great engine
Jim

[tubman]

When I built my latest 258" engine, I used a set of 1/8" over pistons I got from Speedway's "Garage Sale" for about $100 (including pins, clips, and rings). These were 4 ring pistons that i installed without the bottom ring on the advice of a lot of people who should know. I only have break-in time on the engine, but so far I have been very satisfied. I know the juries not in yet, but from all indications this is going to be a good one. See for yourself : https://www.youtube.com/watch?v=deAgpVmvjhU

[flatjack9]

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I'm with Kahuna.

[Frank Miller]

I think porting only benefits at high rpm. It may not be necessary.

[JWL]

There is no harm in porting the rough areas. Low speed torque will not be impacted. However there is harm to be done with relieving. Do not do it. As for a cam, the EAB is a great choice. Almost anything else will reduce power in the RPM range your truck is likely to see.

In the old days I was not in favor of using the Forgedtrue pistons on the street. However, I have adjusted my thinking with Ross pistons. I think they can be set at the minimum clearance and work fine on the street. Do not pay extra for special ring groove machining as you will never see any benefit in your use.

Set the combustion chamber clearances as reasonably close as possible and have fun.

[19Fordy]

Kahuna is correct. The OFFY 4 barrel intake has a 7/8 inch generator/fan mounting offset towards the driver side. Go with something that's centered.

[51 MERC-CT]

Originally Posted by 19Fordy

Kahuna is correct. The OFFY 4 barrel intake has a 7/8 inch generator/fan mounting offset towards the driver side. Go with something that's centered.

I agree that a center mounted bracket mount may be a slightly better choice BUT unless there is fan interference with a fan shroud or any other
component, I nor anyone else will know the difference.

[Scotty's 52 F3]

Good to know about the offset on the Offy. I have the stock 6 blade fan and shroud. I think there is room but, I'll look.

The truck is mainly used as just a cool old cruiser but, I do load it up and use it as a truck as well.

I have 32" tall tires, 3.73 gears and the T98 4 speed if it matters.

I was considering the 465 Holley because it fared better in JWL's dyno tests than the 390 did.

It seems the exhaust didn't matter much in this case. However, since I'm building my own exhaust would a 2 into one system run any different than duals other than how it sounds?

Thanks for all the replies and the video.

[Scotty's 52 F3]

Ross (ALBQF1) has had good results with a Rochester two bbl and the 4 bolt Merc manifold. Would this be a better choice than the small 4 bbl?

[40 Deluxe]

Originally Posted by drolston

Looks like you will end up with 270 or so cubic inches. The 390 CFM Holly might be better suited than the 465. Relieving the area between the valves and cylinder is worth the time and effort.

No, do not relieve the block! That is an out-dated "speed trick" that only serves to lower the compression and gives negative results, except maybe in an all-out high RPM race engine. Compression is your friend!
Consider: Air has weight, thus inertia, and so does not like to turn corners. Every bend in the intake tract slows air flow. When the air/fuel mixture flows past the intake valve it is traveling upward, toward the head and is forced down into the cylinder at the transfer area. Since air wants to go straight, following the path of least resistance, very little air will flow through the block relief. It just won't make that sharp turn very effectively. Now, if you're cramming the air/fuel mixture in with a supercharger, relieving may help, but I don't think the relief area is the biggest restriction to intake flow. More likely, it's coming through the intake port, making that sharp bend.
Remember, air is never pulled into the cylinder, it is always pushed in. You can't pull a fluid, you have to push it. Atmospheric pressure does the pushing. We may mistakenly picture the piston pulling air in through that nice relief we just ground into the block, but not so!

[GOSFAST]

If you choose the right parts, all depending on your budget, you can do about 150 HP and 250# Torque. These numbers will move your ride nicely!

Thanks, Gary in N.Y.

P.S. All this with NO porting whatsoever!

[Scotty's 52 F3]

Looks like relieving not going to be in the recipe. Gary I'm all ears to the "right parts".

[drolston]

To relieve or not relieve? A never ending debate.

The engine I just built was factory relieved. The fact that FoMoCo eventually decided it was a good way to improve performance is all the convincing you should need. The loss of about 3cc of combustion chamber volume only costs about .2 to .3 of compression ratio. You can still easily get to 8.5:1 which is the point of diminishing returns for compression on a flathead. Reference article regarding relieving and for dyno test of increasing compression:

http://www.hotrod.com/articles/0905s...lathead-myths/

Look at the cross section showing relief between the valves and cylinder and you can see where it opens the transfer area by a significant amount. If the object is to get the most fuel mixture into the cylinder in the shortest time, that flow restriction has to be important. I will see if I can find dyno tests on before and after block relief.

No offense to those that believe otherwise. Probably none of us could tell the difference of 10 horsepower in every day driving.

[Ol' Ron]

I don't believe in relieving the block, but to each his own. I do believe in a tight piston to head clearance. Mill the head for .045/.050" clearance. it one of the cheapest mods you can make with noticeable results.

[Scotty's 52 F3]

Ol' Ron, after reading all your posts about squish it's definitely in my plan.

I don't mean to spark debate over relieving a block. This is my first Flathead build and most info on the web involves mods for higher revs. I'm all ears for this torque build.

Thanks to all that offer advice. I do appreciate it.

Some pics of basic port work would be nice if anybody has some.

[flatheadmurre]

If the engine will be run as a truck the relieve has a pro widening the flat area between the valves/cylinders preventing cracks from heat.

[JWL]

FoMoCo never decided to broach the transfer area because it was a performance enhancing technique. It was done to help prevent crack formation at the upper level of the eyebrow. The only debate is about whether or not it was helpful in that regard.

[40 Deluxe]

Originally Posted by JWL

FoMoCo never decided to broach the transfer area because it was a performance enhancing technique. It was done to help prevent crack formation at the upper level of the eyebrow. The only debate is about whether or not it was helpful in that regard.

I haven't had experience with factory relieved blocks. Do they crack any less often than non-relieved blocks?

[flatheadmurre]

Originally Posted by 40 Deluxe

I haven't had experience with factory relieved blocks. Do they crack any less often than non-relieved blocks?

Instead of the narrow top area between valves and cylinder the wider area you get from the relieve is distributing the heat better and cracks don´t have a good sharp edge to start from.

[supereal]

Porting and relieving is usually not worth the effort, and only then if you have experience in doing it. Last year a customer brought in his T-Bird that he bought on line. It didn't run right, particularly at low speeds. We pulled the heads and found that someone had relieved the block so far that the top piston ring was exposed! The only "fix" was finding a different block, not an easy or cheap proposition.

[flatjack9]

What engine was in the T-bird?

[scooder]

A flathead Tbird??

[Ross F-1]

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I think he means it was decked? Surely an OHV Y-block?

[flatjack9]

That had to be one hell of a decking job if the top ring was exposed. Something does not add up. How would you ever get an intake manifold to fit if it was a Y block.

[JSeery]

This is the second time supereal has posted something about a T-bird having what sounds like a flathead engine problem. Wish he would elaborate.

[Lawrie]

Is there not some debate over why the truck blocks were relieved, this is in regards to the 99a engines.
Lawrie

[flatjack9]

Originally Posted by JSeery

This is the second time supereal has posted something about a T-bird having what sounds like a flathead engine problem. Wish he would elaborate.

I was going to say the same thing, but couldn't remember for sure.

[flatheadmurre]

Originally Posted by Lawrie

Is there not some debate over why the truck blocks were relieved, this is in regards to the 99a engines.
Lawrie

Two reasons come to mind right away...less risk for cracks and to lower compression driving them hard with the less good fuel back then.

[Lawrie]

Why would the relief lessen the chance of cracking,would you not be better off with more metal in that area,also if they wanted to loose some compression why not use a cyl head with a larger chamber,like 81T or the like.and the relief only takes a small amount out off the chamber
Lawrie

[HotRodmicky]

I wouldnt relieve it for an even simpler reason ....
Its tough to get the pistion rings in the bore.
Double tough if have metric rings ( which i would use)

[flatheadmurre]

Originally Posted by Lawrie

Why would the relief lessen the chance of cracking,would you not be better off with more metal in that area,also if they wanted to loose some compression why not use a cyl head with a larger chamber,like 81T or the like.and the relief only takes a small amount out off the chamber
Lawrie

The sharp small area between valve and cylinder heats/cools faster then a larger flat area.
Any small area heating up faster then the rest of the block under load is a potential problem.
And the difference in heat gives tension in that narrow strip which becomes an excellent place for a crack to start.
Machining nice radiuses on every sharp edge would probably help some to.

[Ol' Ron]

I don't think there is a very good reason for relieving, Yes blending in all the surfaces mighr do the same think and not reduce the CR. BUT!!! These are street engines. Think??

[cdan34]

I have had, through the years, four flatheads. I have relieved them all and the compression was brought up in other ways. I know there is a debate on this one. Here are my thoughts; on the exhaust stroke the pressure is towards the top of the combustion chamber. Likewise the top and side of valves. When relieving you open an area that would let some of the exhaust out 90 degrees
to the valve. I think this would help relieve pressure. Wouldn't that be a good thing ? I don't know about the horsepower gain and some of you guys are much more involved in this then I am.

So what is lost by relieving the block ? I would think the engine could breath better.

cdan34

[Kahuna]

Scotty
Another thing might be to rethink the transmission. Maybe the std truck 3 speed would be a better option, unless you really need that real low 1st gear?

[JWL]

I have seen only a few factory relieved blocks. Probably a dozen or less. A few(I think 3) were cracked This might be a slightly lower percentage than non-relieved blocks.

When the exhaust valve opens there is a "blow-down" of pressure because the entire chamber contains combustion pressure. That is why the exhaust has such a loud sound. There can be 80 or more PSI blasting out of the chamber(depending on the engine).

After conducting more than 400 flow tests I find no reason for relieving unless there is a desire to increase residual exhaust gas contamination or lower the CR.

[tubman]

There are two things that I don't even consider anymore when building a flathead : relieving the block and exhaust dividers. BTW, I have a nice, new pair of the latter in their original packaging; anybody want 'em?

[Scotty's 52 F3]

Kahuna, I don't really NEED the granny gear. I have only used it starting out on hills when I loaded the heck out of the truck. The engine is really tired though. I may not have to use it when I have a fresh engine.

I have thought about a T5. The T98 works and is paid for so it'll have to do. I may gradually collect what I need to swap another trans at a later date though.

I trying to keep it a freshened up old truck more than turning it into a street rod. I have to admit, an overdrive would really be nice though.

Budget is a big concern. It's taken me two years to go through all the systems as I drove it. A little at a time as I could afford. It's time to tear it down for body, paint and engine rebuild.

Thanks for all the replies.

[40 Deluxe]

Originally Posted by HotRodmicky

I wouldnt relieve it for an even simpler reason ....
Its tough to get the pistion rings in the bore.
Double tough if have metric rings ( which i would use)

Just make sure all the ring gaps are on the other side of the piston. It's a ring end that likes to pop out.

[Henry Floored]

Well gang EVERY Flathead block I have ever seen is factory relieved. That big eyebrow cast or machined into the deck around the valves is a flow relief.

If you wish smooth the edges and radius the top edge of the cylinder that is in between the head gasket. I doubt anything more would be of help though I've got no flow numbers to prove it either way.

The idea of the transfer area in a Flathead Ford is to turn the mixture down into the cylinder because the flow wants to go straight up.

This is the plight of any side valve engine.

Ford Flatheads are actually quite sophisticated in this area. Pull the head off any side valve lawnmower engine and you'll see what basic looks like.

The early racers had it right, (remember it took a while and a bunch more cubic inches for the OHV's to start beating the Flatheads on the salt) when they started "popping" the piston up into the head and greatly reducing the impediment to flow without giving up compression.

I can't think of one reason why even a street performance engine couldn't benefit from this other than extra cost.

[Henry Floored]

Here is a good read on the matter.

http://www.navarroengineering.com/high_dome.html

[70mach1]

So I have read through all of the posts with interest but my situation is different than the OP. Here is a little background: I have a 28 AV8 Closed Cab Pickup that I am setting out to rebuild the 8BA that I installed into it earlier this year. I bought the engine locally dressed out with some performance items. The engine has Offy .400 heads and a dual carb intake with 2 -97s on it. I have an HEI distributor on it as well. It is supposed to have a Potvin 3/8 cam in it. The truck drives great and feels quick, even with the 3-3/4 stroke and .030 over it currently is. The only real performance issue I have with the truck is torque related. I have an RTS Overdrive behind the engine and 3.78 gears with a 7.00X16 rear tire. That translates to 2000rpm at 70. The truck does not have enough power to pull hills in overdrive at 70-75mph. I have a LOT of blow by and excessive oil consumption, hence the rebuild. I plan to do any porting and relieving myself, I am a toolmaker and have done other engines, this is my first Flathead. I have already purchased a SCAT 4-1/8" stroker kit with the .125 over Ross pistons, bearings and gaskets for a 284" build. Here are my questions:

1. I get that relieving might not be worth the money if you are paying someone to do it, but doing it myself is it a bad idea for any reason? I would think that the main point of this mod is to unshroud the valves to use OHV speak. So, maybe not a full relief, but at least bringing the block down around the low side of the valve and blending with a more gentle slope up to the deck? This would serve most of the benefits of relieving without as much of a compression loss.

2. My performance issue can also be solved by changing my 3.78 gears for an already purchased set of 4.44. But I was hoping to gain enough power with the extra bore and stroke to keep my RPMs in the basement while cruising. I have gotten advice to ditch the Potvin cam for a 1007B Isky. Do y'all concur?

[flatjack9]

With that cam you are probably down on torque at that rpm compared to a stock cam. Obviously you will pick up torque with the increase in stroke. I would maybe clean up a few of the sharp corners in the ports and forget the relief. It will do you no good in the rpm range you are talking about. Just tell everyone it's ported and relieved. The 1007B is a good choice for a street cam.

[JSeery]

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It's mostly an RPM issue.

[Tim Ayers]

Originally Posted by Henry Floored

Well gang EVERY Flathead block I have ever seen is factory relieved. That big eyebrow cast or machined into the deck around the valves is a flow relief.

If you wish smooth the edges and radius the top edge of the cylinder that is in between the head gasket. I doubt anything more would be of help though I've got no flow numbers to prove it either way.

The idea of the transfer area in a Flathead Ford is to turn the mixture down into the cylinder because the flow wants to go straight up.

This is the plight of any side valve engine.

Ford Flatheads are actually quite sophisticated in this area. Pull the head off any side valve lawnmower engine and you'll see what basic looks like.

The early racers had it right, (remember it took a while and a bunch more cubic inches for the OHV's to start beating the Flatheads on the salt) when they started "popping" the piston up into the head and greatly reducing the impediment to flow without giving up compression.

I can't think of one reason why even a street performance engine couldn't benefit from this other than extra cost.

Ross now makes pop-up pistons that are about 1/2 the cost of the Arias ones.

[Ol' Ron]

The cam might have too much overlap. I'm running the EAB cam with the 280 and the torque is fantastic. This business with the relief is not worth the effort. Maybe if you were running Bville.
I went up Weston hill in Vermont (14%) started at the bottom in oD at 50MPH and cleared the top at 43 Engine was turning 1300 RPM. You have to have a reason to make a modification.

[Tim Ayers]

Originally Posted by 70mach1

So I have read through all of the posts with interest but my situation is different than the OP. Here is a little background: I have a 28 AV8 Closed Cab Pickup that I am setting out to rebuild the 8BA that I installed into it earlier this year. I bought the engine locally dressed out with some performance items. The engine has Offy .400 heads and a dual carb intake with 2 -97s on it. I have an HEI distributor on it as well. It is supposed to have a Potvin 3/8 cam in it. The truck drives great and feels quick, even with the 3-3/4 stroke and .030 over it currently is. The only real performance issue I have with the truck is torque related. I have an RTS Overdrive behind the engine and 3.78 gears with a 7.00X16 rear tire. That translates to 2000rpm at 70. The truck does not have enough power to pull hills in overdrive at 70-75mph. I have a LOT of blow by and excessive oil consumption, hence the rebuild. I plan to do any porting and relieving myself, I am a toolmaker and have done other engines, this is my first Flathead. I have already purchased a SCAT 4-1/8" stroker kit with the .125 over Ross pistons, bearings and gaskets for a 284" build. Here are my questions:

1. I get that relieving might not be worth the money if you are paying someone to do it, but doing it myself is it a bad idea for any reason? I would think that the main point of this mod is to unshroud the valves to use OHV speak. So, maybe not a full relief, but at least bringing the block down around the low side of the valve and blending with a more gentle slope up to the deck? This would serve most of the benefits of relieving without as much of a compression loss.

2. My performance issue can also be solved by changing my 3.78 gears for an already purchased set of 4.44. But I was hoping to gain enough power with the extra bore and stroke to keep my RPMs in the basement while cruising. I have gotten advice to ditch the Potvin cam for a 1007B Isky. Do y'all concur?

I'll admit that I didn't read your post that closely, but it sounds like your motor is on the decline, so I'm not sure it's fair to judge performance modes done on a weak engine.

Somewhere on the interwebs is Mike Bishop's porting guide. Google it and when found, print two copies. One for your night time reading and one to keep next to you as you are working on the engine in the shop.

Other may know, but I'd do the math of what the O/D will make those 4.44's. That is a steep rear. I also believe that Potvin 3/8ths will wake up a bit with the large CI and stroke.

[Binx]

Here's one of Ol' Ron's posts that I have in my recipe book...

"Take a 258ci with 39-41 "A" heads, that's 8:1 CR. Add a 2GC or Holley 2110 carb from a 55-6 truck and you have axle breaking torque."


Lonnie

[Ol' Ron]

I made a mistake on the 81A head. I think it was the 81s head which is sometimes called the 'Denver head" I learn allot after building many engines and sometimes I get mixed up on just what I did. But I will stand by the piston to head clearance as being a very good mod. As it improves drivability as well as economy, for very little cash.