Relieving 8BA Block
 

Should a block for a street car be relieved 286 ci

Re: Relieving 8BA Block
 

The first sentence in the Relieving the Block section Ron Halloran's book NOSTALGIA-Rebuilding and Modifying the Flathead V8 (Page 39) says:"Relieving the block is usually reserved for racing engines." He then goes on the explain."The reason an engine needs relieving is to produce power at high RPM's and that's not where a street engine spends much of its time." Also, read all of this:
http://www.flatheadv8.org/rumblest/intro.htm and
http://www.jalopyjournal.com/forum/t...eading.770895/

Here's a couple of good articles:
http://www.hotrod.com/how-to/engine/...lathead-myths/
and
http://www.jalopyjournal.com/forum/t...inions.420484/

Re: Relieving 8BA Block
 

It all depends on your complete setup, how you plan to use the engine and what RPM range you want to run at.

Typically, relieving a block will not help lower-end torque or horsepower, will probably hurt it as you lower compression a bit. If you desire peak horsepower and plan to regularly ran it over 4,000 RPM, then it can help flow. Also, relieving by itself will probably not help a bit - so unless you do a full competition style port job and install bigger valves, probably isn't worth it.

What combination of parts in the engine (cam, intake, carbs, ignition, heads, compression ratio), what trans, what gear ratio and what are you looking at as far as usage and engine behavior.

Also, you might consider more of a 'step relief' or semi-relief, where you blend/smooth the valve pocket cuts into the transfer area to help the flow, but not hurt compression too much.

Best of luck - if you need more info, PM me.

Dale

Attached are some pictures of various reliefs I've done (full, stepped, semi) - mostly Ford, but also Flathead Cadillac:

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Attachment 228194

Re: Relieving 8BA Block
 

Air flows the best in a straight line. Anytime you force air to change direction, flow is reduced. So you want these changes to be as gradual and as smooth as possible. Thus the major air flow is out of the port and up against the head surface and then down into the cylinder, kind oaf a gradual arc. Relatively little air flows directly along the deck surface into the cylinder. Of course, in a high RPM race engine, you're after every last bit of flow, so you trade compression for better cylinder filling.

Re: Relieving 8BA Block
 

Relieving will also lower your compression . Personally I want the compression.

Re: Relieving 8BA Block
 

you could ruin good engine if not racing you will always beat your shadow with the sun at your back.

Re: Relieving 8BA Block
 

So why did ford factory relieve the 59AB in their truck engines?

Re: Relieving 8BA Block
 

Since I wrote that book, I've learned that relieving the block is basicaly a waste of time and money, for any aplication. Air flow is controlled by the combustion chamber shape. Relieving the block is just a cure for a bad chamber design.

Re: Relieving 8BA Block
 

Truck engines were relieved to lower compression and reduce hot spot areas that could cause the dreaded ping or detonation under heavy loads.

Re: Relieving 8BA Block
 

George, with the sun at your back, your shadow will always win and in my 35 I'm thinking my shadow might lap me a couple times!

Re: Relieving 8BA Block
 

We'll never solve the question of 'to relieve or not to relieve' - there are more opinions than bung-holes in the flathead world (which makes it fun - you get to pick your fortune teller and make up your own mind). :D

One thing I do believe is that in higher RPM engines having a relief has to improve flow - or Harley would not have done it for 15 years in their racing KR flatheads. In my opinion there is no flathead engine that had more development and dyno time than Harley and their racing KR's. I've had numerous sets of cylinders and heads and my neighbor built a lot of their race bikes. All were relieved - some 'stepped' - as the heads were stepped and in their larger roller cams, they ran dual profile cams. Nobody has achieved their horsepower per cubic inch - naturally aspirated and on gas. With that said - these were highly developed versions of the old 45 CI Harley flathead - our flatheads have nowhere near the optimized port sizes/designs and flow these guys had.

Here are two pictures for you to ponder - two different styles of reliefs:

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Attachment 228251

Re: Relieving 8BA Block
 

Grancor made some heads with Harley combustion chambers?? Had a set that had a pop up design for a 3 3/4 stroke piston on a 4' crank. Heads are now in a junk yard in Yuba city Ca. With the rest of my engine.

Re: Relieving 8BA Block
 

The Navarro 'Hi-Dome' heads are a half-copy of the Harley KR design (in the valve area) - but not down in the combustion chamber area (or the pistons). I talked to Barney at length about doing the whole KR design back in the 80's - but he only wanted to make a certain amount of changes to his regular core boxes - so he made it about 1/2 way there.

On the Flathead Cadillac blown/injected engine that we built for Bonneville (the 'FlatCad'), I adapted the KR design to our head designs (we made them out of billet aluminum) as well as our pistons. My neighbor and I talked at length about whether to go pop-up with a flat-top or domed chamber. He said that Harley came out with a domed pop-up very late in the development, but that it really didn't run any better than the flat-tops (as a matter of fact a bit slower and everybody panicked) - so I went with flat-tops in my 3D CAD designs. Was a lot easier to machine the heads/pistons with a flattop and get the exact quench I wanted.

We've made 650 HP on alky on the engine dyno - our challenge is keeping the head gaskets in it - as the decks are 'thin', just like our Fords.

Here are some pictures:

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Re: Relieving 8BA Block
 

The reason why Ford relieved blocks was because many ford trucks during WWII developed cracks from the valve seat to the bore. This was supposedly because the vacuum boosters caused the mixture to lean out which in turn caused over heating. Relieving the block was the cure.
That's how I remember reading it. I hope that helps.

Re: Relieving 8BA Block
 

The false impression that relieving is good for competition engines because they operate at higher RPM will probably never die. Why? Because visual observations of Flathead flow paths seem to indicate a relief would be an improvement. Only after following the science with back-to-back flow bench and dyno tests can the facts be revealed.

The concept of using "seat-of-the-pants" as a point of reference or to collet data does not bode well for uncovering the facts. The fastest and quickest racing runs I have ever made actually felt the SLOWEST. I think this is because things happen very smoothly during the better runs. Those "hairy" runs with jolting wheel stands and power-drift crabbing at the top end are very impressive, but slow. Often there are those who make reference to speed records as proof of the value of relieving. But, since there are equally, or even more, magnificent records established with non-relieved Flatheads and since there is no way to determine how fast the sited record setter could have gone with no block relief, this is hardly a method which will determine validity.

I have no data on systems operating with air pressure beyond atmospheric.

Re: Relieving 8BA Block
 

Grancor combustion chamber

Re: Relieving 8BA Block
 

The Harley KR flathead using a releived block using atmospheirc air proved with data it is the best way to go on a flathead. :D

Re: Relieving 8BA Block
 

A relief on the Harley KR might have provided a flow or combustion improvement on the Harley KR. My testing has been confined to the Ford Flathead V8 where relieving is a waste of time, compression, and adds to the undesirable residuals in the unswept areas.

Re: Relieving 8BA Block
 

The KR models were a modification of the basic WL cylinder design just like the old Army WLA "45" bike engines had. Since they are air cooled with separate piece design, it made them easy to work with or replicate. The aluminum heads crack easily due to the heat so a person has to stock a lot of parts if they run those old engines on the track. My 1948 WL 45 solo has surface cracks in the top area of the combustion chambers but it still runs OK if you don't let it idle too long. Then again, it's definitely not a KR model. The intake ports and exhaust ports are a lot different than a Ford flathead V8 so it is harder to get a good comparison between the two designs other than they are both flatheads or valve in block types.

Re: Relieving 8BA Block
 

Looks like its best to throw away that die grinder all those wasted hours! I DONT THINK SO

Re: Relieving 8BA Block
 

Anyone seen the Evans heads? They have a raised roof between the piston and valve pockets. Looks like a better choice to relieving.

Re: Relieving 8BA Block
 

This relieving the block has always been fascinating to me. I have done it on a few blocks in the past and I've heard the negative comments. Just with common sense thinking, you know there is pressure in the combustion chamber. Granted it is forced against the top of the head as the exhaust valve is open, and works it's way around the valve into the port. If you have a relief that pressure will also have an open path to under protruded valve directly into port which seems to me would reduce the pressure on the top of head. For the minimum compression loss you can always take some material of the head surface.
The French blocks are nice castings with more nickel for strength and a better exhaust path then Ford. All the ones I've seen are relieved.
I would like to see a dyno test between two naturally aspirated engines, one with relief and one with out. My money is on the relieved engine!

cdan34

Re: Relieving 8BA Block
 

All of the SUMB French engines were army truck engines. Near all of the engines that were purposed for big trucks were relieved. Trucks always needed some help in keeping them from self destructing under hard use. Since gearing made up for the lack of horse power, they needed a change from the stock automobile design to improve long term work performance. Relieving was the fix that FoMoCo engineers settled on since the flathead is so limited with respect to what can be done to it that won't take more away from it's capability to function in order to effect a change. In later years they did more modifications to the heads. The 8RT heads are a good example of a low compression head but when pulling a full load in the old F6, it really made the difference between the roughness of detonation or running smoothly. It was all about warranty consideration and reliability to keep the customer coming back for a new truck every so often. The big F7 & F8 trucks were the first Fords to get the new 317 Lincoln Y-block in 1952 so that they could get away from the flatheads. Even the Lincoln 337 wasn't up to the task well enough for the big trucks so it was finally dropped for the OHV engines.

Relieving was such a mainstay for the old aftermarket aluminum heads with crow foot chambers(that are still available to this day), that it's been viewed by so many to be the performance way to go that it is doubtful that there will ever be an agreement between folks that are all for relieving and those that don't use large reliefs.

Barney Navaro was one of the guys that played with the bent 8 long after most folks were adjusting there rocker arms. He preferred a small relief that basically just made a smooth ramp from the valve seat edge to the edge of the cylinder wall. After all those years of both seat of the pants experimentation and using science to effect meaningful changes, this was what he settled on.

Re: Relieving 8BA Block
 

Re: Relieving 8BA Block
 

2015 thread ???

Re: Relieving 8BA Block
 

New guy, first post. Happens all the time.

Testing the waters, so to speak.

Re: Relieving 8BA Block
 

Exactly the response I expected.

Re: Relieving 8BA Block
 

panic: Thanks for your post. Maybe some here don't realize how much you know about this stuff. Please continue!


Terry

Re: Relieving 8BA Block
 

Panic please repost. That was great info. Obviously you have some special knowledge on the WR/KR. This forum has all types please don’t take any post personal as there are many readers & for everyone that may not be interested in your post there’s possibly many that are. Thanks so much for the opportunity to at least read it once but would love to read again & retain as much of your knowledge as possible.
Cheers
Tony

Re: Relieving 8BA Block
 

"panic" - I think you're reading this wrong. My post was to explain to "Ronnie" what was happening, not to criticize you.

I will however, suggest you develop a slightly thicker skin if you are going to post on internet message boards. There are some that are a lot worse than this one.

As to your post, I found it quite informative.

Re: Relieving 8BA Block
 

Well . . . seems 'Panic' came and went. He might be the same guy that I've seen on other forums (in the past) - most likely the HAMB. Hopefully he has some good information to share, he'll repost it. If he some information about the Harley KR - would love to hear it as my neighbor built many of them for flat-track, Daytona, side-hacks, etc..

There is always more to ponder, learn about, debate, etc -- if one isn't willing to debate ones 'facts' that one posts . . . then it seems a waste to post them.

I didn't get to read the infamous post . . . maybe he'll rethink . . .

Re: Relieving 8BA Block
 

He deleted his post after several of us tried to explain what happened and invited him to stay and contribute. Probably not a greatr loss.

Re: Relieving 8BA Block
 

Engine:
305 ci. Naturally aspirated. Dry sump.
14.5 to 1 compression.
FLAT TOP 2 ring pistons.
307 hp @ 6300 on 118 race gas.
.200 deep relief.

Re: Relieving 8BA Block
 

Just curious: What might the horsepower be if the block were not relieved but instead the same amount of material were taken off the roof of the combustion chamber in the transfer area?

Re: Relieving 8BA Block
 

Pete, you should know that nobody can make horsepower with a relief . . . you should not have tried. I'd fill that relief back in with JB Weld and get your compression up to 16:1 and run regular pump gas. This should give you 308 hp @ 8000 rpm. LOL :D:D

Re: Relieving 8BA Block
 

At 14 CR on a 307 ci engine, The combustion chamber would be so small, not much air would be in there

Re: Relieving 8BA Block
 

What does JWL say about recieving a Flathead block in his book? Did he run Dyno comparisons? What were the results?

Whoop's, just went back and saw his previous post. Never mind :o

Re: Relieving 8BA Block
 

It did not work as well because of the longer path.

Re: Relieving 8BA Block
 

B&S, how come you didn't place the spark plug in the transfer area on the new heads.Just curious./ That
s really a long flame front??

Re: Relieving 8BA Block
 

Thanks for the interesting reply! I didn't think of the longer path as being detrimental. I was focused on the loss of air flow due to the sharper turn from valve to cylinder, caused by the lower roof of the combustion chamber. Always more to think about!