Why do Flathead V8 Blocks Crack?

Johnnydidd said:
Flathead design has caused the cracking, very poor design. If you have flathead you will have the problem sooner or later. Block repair is a good answer, I had one repaired few years ago no problem(cracked from no 2 cylinder to valve seat). My recommendation keep as cool as possible, I am always looking for ways to keep engine cooler. I have a Model A that has been overheated to where it would hardly run no cracking, but look how the exhaust valve is next to the manifold.
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Any cast part is subject to cracking. That is from any manufacturer. Even the much vaunted small block Chevy can acquire cracks.

The Flathead Ford can get cracked in one of three ways usually. One by freezing. Two by over tightening of the too large diameter head bolts. (the Flathead Ford would be better off with 7/16" "torque to yield" stretch bolts, there is simply too much ability to distort and yes crack the deck with the factory fasteners). Third is probably steam pockets as one other gentleman has mentioned, though that is an educated guess on my part. The Flathead block is a complicated casting and as such is quite a technical triumph to be as good as it is. It would be a strong challenge even for today's pattern makers and foundry men to try to duplicate it today.

When you comment that the Flathead is a "very poor design" I have to take issue a little bit sir. I think you might be referring to the internal exhaust porting. While yes that is unique to the Ford Flathead they do not constitute poor design. On the contrary, the exhaust porting was a no compromise solution to the problem of packaging and plumbing.

The Caddys and LaSalles ran exhaust out the top and it's very "busy" on the top of the engine. Intake and exhaust manifolds fighting for the same space.

Pick your poison I guess but the Ford solution is not a poor design in my humble opinion.
 
Henry Floored: How would design the engine if it was up to you? Did Caddy crack as much as Ford? I don't believe so.
 
Johnnydidd said:
Henry Floored: How would design the engine if it was up to you? Did Caddy crack as much as Ford? I don't believe so.
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I would design a Flathead exactly like the Lincoln 337, except for a lighter rotating assembly and possibly 5 main bearings. Other than that the Lincoln 337 is the "zenith" of side valve V8 technology to date.
 
Johnnydidd said:
Henry Floored: How would design the engine if it was up to you? Did Caddy crack as much as Ford? I don't believe so.
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The thing is that a Cadillac's price was multiple Ford's, and so was a Lincoln. Ford's secret to success was providing an eight cylinder engine to the masses for the same price as the competitor's six.
 
I HAVE SEEN a flathead Ford with no cracks. It is an NOS block, but it has no cracks. :)

I can't remember seeing any others without cracks though.
 
scooder said:
Don't know why, but in my experience the later (8BA) type blocks seem to more likely crack from valve to bore than the prewar blocks. Anybody else found this? Or am I lucky on the prewar blocks?
Martin.
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It's the first time I've read about this but for what it's worth, the Canadian 8BA blocks we have here in New Zealand seem much more prone to cracked valve seats than earlier Canadian blocks. C59A and C69A blocks usually have the "Ford part #" cracks but rarely any others.
If I had my druthers I wouldn't use an 8BA in a performance application but I read about others who do, apparently successfully, so I wonder; are some 8BAs more prone to cracking than others?
 
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when I rebuilt my 53 merc engine the machine shop said it was the first flathead they had seen with no cracks. my lucky day. Paul
 
Im not sure how well the formula of the material was kept uniform during the years and between different foundrys.
If one was to cast a new block without counting dimes adding a higher nickel content and some other tricks would do wonders.
The flathead is an amazingly good compromise between weight/size/performance/cost.
Starting to add separate exhaust you get a bigger/heavier engine.
 
If Ford somehow could resurrect a new Flathead block with a few improvements it would be tremendous. Compared to some of the money spent on other things a Flathead block would be a drop in the bucket.
 
Since I was challenged earlier on how "I" would build a Flathead I'll go ahead and explain that.

I would put a carefully shaped intake port in it with a great "short side" radius in it.

In the exhaust ports I would fill in the dam at the end exhaust ports. That would be a smooth ramp to help the exhaust out.

The center exhaust port would be split by a separating wall. All the exhaust valve pockets would be more like an upside down OHV valve pocket.

No more removable guides!

Camshaft would rube in 5 bearings and be larger in diameter.

For a "shoot for the moon" option I'd put 5 mains in her with a light rotating assembly and as big a bore I could fit in there.
 
If youre redesigning for better performance why not go with a new crank to solve the firing order...taking care of the shared exhaust port.
Problem is your flathead wont sound or be the same anymore...:D
 
flatheadmurre said:
If youre redesigning for better performance why not go with a new crank to solve the firing order...taking care of the shared exhaust port.
Problem is your flathead wont sound or be the same anymore...:D
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The shared ports don't suffer from a firing order problem. They suffer from a shared port problem.
 
flatheadmurre said:
If youre redesigning for better performance why not go with a new crank to solve the firing order...taking care of the shared exhaust port.
Problem is your flathead wont sound or be the same anymore...:D
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Hence the wall between the center exhaust ports at least to a reasonable distance into a shared exhaust passage.
 
Its a hard task to solve real good without changing the outside dimensions.
A baffle to guide the flow of the exhaust is a good bit on the way.
I was more thinking crossfire or something real drastic :D
 
flatheadmurre said:
And whats the problem with sharing a port ??
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The only problem with sharing a port is that the shared ports see twice as many hot exhaust charges, yet they are structured and cooled the same as a non-shared port.

In my opinion, the real problem with Ford flatheads is the fact that the exhaust travels a painfully long and crooked path inside the block before it exits. Just look at all the 90 degree turns it has to make before leaving. Cadillac put the exhaust ports on top, resulting in an unorthodox looking engine that performed better.
 
Henry's insistence on doing things his way was always with a purpose, to solve or prevent a known problem. He routed the exhaust through the block in order to heat the cylinders as quickly as possible, knowing that cold starts are the most destructive to an engine. As is usually the case, solving one problem creates another.
 
ford38v8 said:
Henry's insistence on doing things his way was always with a purpose, to solve or prevent a known problem. He routed the exhaust through the block in order to heat the cylinders as quickly as possible, knowing that cold starts are the most destructive to an engine. As is usually the case, solving one problem creates another.
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If you look at an inline flathead (Ford and all others), the intake and exhaust ports are on the same side as the intake and exhaust valves, therefore they don't have Ford's intentional cylinder-heating as you described.

The problem with joining two inline flathead fours in a "V" is that it is desireable to have the intake and exhaust in a "cross flow" configuration, but there's no practical way to have the valves on opposite sides of the same cylinder bank, so instead they just routed the exhaust out the opposite side by creating ports inside the block. Cadillac decided to put both ports on the "inboard" side.
 
Mike51Merc said:
The only problem with sharing a port is that the shared ports see twice as many hot exhaust charges, yet they are structured and cooled the same as a non-shared port.

In my opinion, the real problem with Ford flatheads is the fact that the exhaust travels a painfully long and crooked path inside the block before it exits. Just look at all the 90 degree turns it has to make before leaving. Cadillac put the exhaust ports on top, resulting in an unorthodox looking engine that performed better.
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Theres a little bit more to it then just the heat...

To get a motor perform real good you should have a skavaging effect.
And you want the cylinders sharing port to fire as far apart as possible.
And on top of all performance aspects you want a well balanced engine and not a pogo stick under your hood.
 
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