I dissasembled the flathead V-8 that came with my 1940 pickup project.
Somebody left the carb off of the manifold letting rust grow in two cylinders that had the intake valves open. The funny thing is those two pistons weren't frozen. The no.3 cylinder is frozen with both valves closed. There is a fine layer of corrosion on the cylinder wall both above and below the stuck piston.

Do any mechanics out there know if that means the block is cracked? Could that condition happen without the block being cracked?

 

>I dissasembled the flathead V-8 that came with my 1940
>pickup project.
>Somebody left the carb off of the manifold letting rust grow
>in two cylinders that had the intake valves open. The funny
>thing is those two pistons weren't frozen. The no.3 cylinder
>is frozen with both valves closed. There is a fine layer of
>corrosion on the cylinder wall both above and below the
>stuck piston.
>
> Do any mechanics out there know if that means the block is
>cracked? Could that condition happen without the block being
>cracked?


It could be a number of things. Usually when one cylinder is different, that is the place to look for trouble. You'll just have to do some investigating while you take it apart. Look for signs of antifreeze in the crankcase - you'll see a 'high water mark' on the crank lobes if it was leaking. Check to see if your pan rails are ok.

Also look for signs of a blown head gasket over the #3 cylinder. If it was dumping coolant into the cylinder while it was running that cylinder will be cleaner (carbon deposits) than the others.

Clean out the rust and look closely at the top of the cylinder wall where the intake or exhaust valves are. What you're looking for is a fine hair-like line. Cracks close pretty tight when the block cools. With rust above and below the piston, it's possible the crack extends down the side of the cylinder wall. Good luck, and give us a play by play of what you find.