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Old 06-18-2015, 10:22 AM   #1
1934calkid
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Default Relieving 8BA Block

Should a block for a street car be relieved 286 ci

Last edited by 1934calkid; 06-18-2015 at 10:39 AM.
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Old 06-18-2015, 10:55 AM   #2
19Fordy
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Default 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/

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Old 06-18-2015, 11:05 AM   #3
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Default 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:

Relief1 copy.jpg

DeckAtAngle.jpg

59L-Porting-Guides-Relief-80.jpg

ReliefWithRadiusBoreEdge copy.jpg
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Old 06-18-2015, 11:20 AM   #4
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Default 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.
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Old 06-18-2015, 11:22 AM   #5
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Default Re: Relieving 8BA Block

Relieving will also lower your compression . Personally I want the compression.
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Old 06-18-2015, 11:56 AM   #6
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Default Re: Relieving 8BA Block

you could ruin good engine if not racing you will always beat your shadow with the sun at your back.
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Old 06-18-2015, 03:48 PM   #7
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Default Re: Relieving 8BA Block

So why did ford factory relieve the 59AB in their truck engines?
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Old 06-18-2015, 04:15 PM   #8
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Default 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.
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Old 06-18-2015, 05:41 PM   #9
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Default 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.
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Old 06-18-2015, 05:41 PM   #10
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Default 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!
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Old 06-18-2015, 07:51 PM   #11
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Default 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).

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:

01p-1965-krtt-head-barrel-2.jpg

user3389_pic8514_1309048160.jpg
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Old 06-18-2015, 09:41 PM   #12
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Default 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.
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Old 06-19-2015, 04:31 AM   #13
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Default Re: Relieving 8BA Block

Quote:
Originally Posted by Ol' Ron View Post
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.
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:

Head1_ChambersHandPolished.jpg

Chamber_HandPolishedAndORinged.jpg

PistonPopUp.1.jpg

EngineBlowerDriveMockup101.jpg
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Old 06-19-2015, 06:20 AM   #14
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Default 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.
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Old 06-19-2015, 06:42 AM   #15
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Default 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.
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Old 06-19-2015, 10:26 AM   #16
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Default Re: Relieving 8BA Block

Grancor combustion chamber
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File Type: jpg grancor combustion chamber.jpg (37.6 KB, 155 views)
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Old 06-19-2015, 06:50 PM   #17
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Default Re: Relieving 8BA Block

Quote:
Originally Posted by JWL View Post
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.
The Harley KR flathead using a releived block using atmospheirc air proved with data it is the best way to go on a flathead.
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Old 06-20-2015, 05:23 AM   #18
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Default 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.
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Old 06-20-2015, 07:16 AM   #19
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Default 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.
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Old 06-20-2015, 05:30 PM   #20
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Default Re: Relieving 8BA Block

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