Why do Flathead V8 Blocks Crack?
 

I have owned many flathead engines over the years. Some were perfect with no cracks and some had cracks. Sometimes the cracks caused problems and other times not and didn't even know about them until rebuild time came around.

The cracking I remember was mostly in the area of the valves. Seat to seat and seat to cylinder bore. Sometimes the cracking was due to coolant freezing but this should be expected if you don't keep proper strength anti-freeze in the engine.

I was under the impression that the non freezing cracks were due to some casting flaws or temperature overheating and cooling but I was never sure. I know I threw more than one block away due to excessive non repairable cracks.


Can anyone provide a better explanation?

Re: Why do Flathead V8 Blocks Crack?
 

Well, the cracks from the center head studs to the water jacket actually were part of the design process. They were put in to relieve stress between the cylinder walls.
The other cracks, I'm sure, were a result of the way these engines were treated, back in the day. Too many overheat cycles, and or freezing in the winter contributed to most.

Re: Why do Flathead V8 Blocks Crack?
 

Other cracks probably came about from overheating issues. The earlier blocks had plenty of sand left in them once they left the factory, resulting in some overheating. The treatment or inadequate treatment of the overheating issues were probably more cause for cracking than anything else. If you ever talk to H&H flathead they will tell you they have never come across a cracked flathead block they could not fix. I certainly would not pay for their rebuilt engine prices knowing that but I am sure there are many who have and had no issues.

In my limited experience I have dug out a gallon pail or more of sand out of several 59ab blocks. These blicjsca a were relatively crack free and have severed me well since their rebuilds.

I guess, in the end, it's a bit if luck, acquired knowledge about overheating, and how you drive and build them that really determined whether you have a really good block or not that will not overheat. Sorry to have rambled a bit ...

Re: Why do Flathead V8 Blocks Crack?
 

Well if you take a perfect block of cast metal and you heat and cool it for 80 yrs, let's say at least 200 times a yr. that's 16,000 heat cycles. Well you have a used flathead. Kind of amazing they hold up as well as they do.

Re: Why do Flathead V8 Blocks Crack?
 

Come on Ralph, you're not serious, are you?! I have heard this comment made many times as a joke, because this type of crack is so common-such as "Ford assigned a part number to these cracks", etc. I seriously doubt, though, that they "were part of the design process"!!!

Re: Why do Flathead V8 Blocks Crack?
 

I have thought about the idea of heat threating a block to releave the stress and then throwing it in the dark hiding to sit and age....
Thats what you do with a new cast iron piece but should it add something to an old block and how much ?
Have any of you guys some of the valvepocket sleeves left ?
I still have the kit but im not shure if i have any sleeves.

Re: Why do Flathead V8 Blocks Crack?
 

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.

Re: Why do Flathead V8 Blocks Crack?
 

All the exhaust created by the engine gets routed to the outside of the block through the water jackets. The center exhaust port handles 2 cylinders and concentrates more heat there. I believe this fact contributes more to the non freeze cracks then anything else.

Re: Why do Flathead V8 Blocks Crack?
 

Overheat is the only thing that I believe causes the cracks, Not heat cycles

Re: Why do Flathead V8 Blocks Crack?
 

I was joking, of course :), but I have rarely seen a block that didn't have those cracks.

Re: Why do Flathead V8 Blocks Crack?
 

Scooder, I'm with you on that...the prewar blocks had better [in my opinion] metallurgy than the stuff cast post war. Definitely different composition of iron. [Less nickel?]

Re: Why do Flathead V8 Blocks Crack?
 

I was told that the 8BA blocks for the 1953 model year did not have hardened valve seats - that the block itself was used as the valve seat and that rotary valves were used to compensate for wear. Could this be the cause of "valve to bore" cracks in 8BA blocks?

Re: Why do Flathead V8 Blocks Crack?
 

The 8BA ones I've seen with cracks from the valves, did have the hardened seats.
Martin.

Re: Why do Flathead V8 Blocks Crack?
 

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.

Re: Why do Flathead V8 Blocks Crack?
 

There is a big difference between overheating and running an engine to cool! All engines need to run at as high a temperature as is practical.

Re: Why do Flathead V8 Blocks Crack?
 

The problem with overheating (to the point of boiling over) is the steam pockets that form from the loss of coolant. The pockets can allow superheating conditions to occur and the hottest spots in a flathead block are the Siamese exhaust passages. This is why a lot of flatheads have cracks in the middle cylinder exhaust ports up to the valve seats.

The moral of the story is to never allow your flathead to boil over. It's one thing to get hot, it's entirely another when it gets so hot that it blows out the coolant like a geyser.

Re: Why do Flathead V8 Blocks Crack?
 

Pardon me, Ralph! I did take you seriously. Sorry about that!

Re: Why do Flathead V8 Blocks Crack?
 

I figured it sounded more technical than the Ford assigned part number. One of these days I may get lucky and get to see a NOS V8 block!

Re: Why do Flathead V8 Blocks Crack?
 

This is something that I have also wondered about. I'm thinking back to the 50's, when I worked in a small independent garage. We saw mostly 'abused' cars, usually not ones that looked well cared for. I'm pretty sure I can't recall an 8BA that didn't have a crack. I saw 59 & earlier with cracks, too, but it seemed a lot less frequent. Coincidence? Imagination?
I'm sure guys like Pete, Ron, John, and other builders that see lots of engines, would have a better 'take' on this.

Re: Why do Flathead V8 Blocks Crack?
 

It's easy to look back and say poor design, but look at the times: V engines up until then were multi-piece castings with much room for tolerance stack-up and leak points. The crankcase was cast and machined, the cylinder blocks were cast and machined top and bottom with lots of bolt holes to drill and tap, and the heads had to be cast and machined, plus other bits adding to the complexity and cost. Ford's engineers decided to put the complexity into a one-piece block/crankcase assembly so once they had the design down and the molds figured out, they began saving money by doing far less machining. Plus, money was scarce-depression years.

Re: Why do Flathead V8 Blocks Crack?
 

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.

Re: Why do Flathead V8 Blocks Crack?
 

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.

Re: Why do Flathead V8 Blocks Crack?
 

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.

Re: Why do Flathead V8 Blocks Crack?
 

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.

Re: Why do Flathead V8 Blocks Crack?
 

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.

Re: Why do Flathead V8 Blocks Crack?
 

Caddy also had a good eight years of watching and learning from Ford.

Re: Why do Flathead V8 Blocks Crack?
 

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?

Re: Why do Flathead V8 Blocks Crack?
 

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

Re: Why do Flathead V8 Blocks Crack?
 

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.

Re: Why do Flathead V8 Blocks Crack?
 

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.

Re: Why do Flathead V8 Blocks Crack?
 

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.

Re: Why do Flathead V8 Blocks Crack?
 

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

Re: Why do Flathead V8 Blocks Crack?
 

The shared ports don't suffer from a firing order problem. They suffer from a shared port problem.

Re: Why do Flathead V8 Blocks Crack?
 

And whats the problem with sharing a port ??

Re: Why do Flathead V8 Blocks Crack?
 

Hence the wall between the center exhaust ports at least to a reasonable distance into a shared exhaust passage.

Re: Why do Flathead V8 Blocks Crack?
 

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

Re: Why do Flathead V8 Blocks Crack?
 

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.

Re: Why do Flathead V8 Blocks Crack?
 

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.

Re: Why do Flathead V8 Blocks Crack?
 

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.

Re: Why do Flathead V8 Blocks Crack?
 

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.