Why do Flathead V8 Blocks Crack?

Admiral said:
This has been my experience as well. The late-run blocks seem to have more cracking issues than earlier examples; casting quality also appears a little rougher, with far more flash and core wire hanging around.
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I know this thread is pretty long in the tooth but it piqued my interest (too much time on my hands?) I agree with Admiral about the late-run castings. I had a '53 block repaired and the guy said as he was drilling it for pinning he was hitting hard and soft spots in the cracked area (exh. valve seat to cylinder). This indicates to me that the alloy wasn't well homogenized before it was poured. The hard and soft spots set up stress areas due to differential expansion. Stress will relieve itself given an opportunity such as overheating. I believe the foundry did a slipshod job of mixing the alloy. Not on all of them, mind you, but on enough of them to give the late blocks a reputation.
 
The problem is exhaust gas is routed up and then does a u turn out the side of the block. The problem is the head functions are in the block instead of the head itself. Think about all the heads on other engines today that crack. Much more than even the flathead. That's a characteristic of combustion and the firing chamber and valves. Problem is the flathead had the valves in the block instead of in the throw away heads of today. Especially aluminum heads of overhead engines are cracking like crazy, even today. Ever take a Honda or Toiletta apart?
 
Fact fiction or a myth. Back when these were the top guys class A divison, oval track racing. No body ran a late engine. All were the 239 AB's with 42 to 48 bodys. So the
race track gossip was, many engines like 49 to 53 may be from a truck who knows.
All agreed, when worked to death and thermostats opened, a rush of cold water made
these cracks, I just don't know, but does make sense, I think. Then a couple of 49 coupe shoe box'es : never did anything, just the ride for 'last'.. We, number #93 did one 1 first and constant 2&3, we were hot. Never blown an engine either. Oh yeh one
V8 General Mess of Crap, I think a 283. Now watch the Fords go by !!
What ever I sell my self to jump back to those times: the smell of hamburgs smothered with onions beer and nitro methane good times yes ole Ron...sam

Oh my eyes are a running from the nitro. Seekonk speedway, Mass & Thompson CT.
 
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