Well ive been having what I thought was a over heating problem with my 31 ford, but the more I read I'm starting to think I might have a blown head gasket or maybe even a cracked block. When I drive and put the car under load foam comes out from the rad cap. Lots of foam... It does seem to use a little water but I just figuared it was getting hot and dissapearing down the overflow tube. I still need to pull the plugs and do a compression check.
I hope it's a blown head gasket and not a cracked block! Some times block cracks only open up when you get the motor good and warmed up. Get a tester from a radiator shop and see if its exhaust gas that's making bubbles. if it is exhaust (you can some times smell it) I would try block sealer before tearing it down.
I would run a compression test, look for lower pressure. This is where to start. If two cylinders next to each other both have lower readings then it is blown between cylinders. Also check the head nuts as this is very common reason for blown head gaskets. Some times just tightening the head nuts will help.
Do as you wish but if I were in your shoes I would be doing a Leak-Down test instead of a compression test. Injecting 100 # psi into each cylinder while the piston is at TDC may tell you one thing. If two adjoining cylinders that have air injected cause a bubbling water in the radiator, then you have a great place to start exploring.
The blocks are bad about cracking exhaust seats. McKees Antique Engines told me that unless the valve seats were replaced when fairly new they will be cracked mostly in the 2 center cylinders. People poured boiling water in then in the cold winters causing it according to him.
A**** 1000's other things in a 2 hour conversation at his place. What a cool guy, talks like WC Fields
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