Re: 1940 356 engine problem

Posted by Owen_Dyneto On 2013/1/31 9:48:26

Other than finding an NOS head, finding a cylinder head with a known history as to any past milling is not likely to happen and the only practical way to determine if it has been milled before is to "cc" the combustion chambers. This is why it's important to do a "dry fit" of the head after milling to insure there is enough valve clearance. In a few cases of desperation I've successully used a Dremel to grind a bit of valve clearance into the head. Done with care it's a better answer than using double headgaskets which rarely works for more than a couple of hundred miles at best.

In this case the poster says it was milled only 0.012" which is fine, except you don't know that it wasn't previously milled, perhaps more than once. What happens with insufficient clearance is that one or more valve heads will hit the head which can (will) bend the valve head which prevents the valve from sealing. That's why, after milling ahead, it's always important to check the clearance. There are a couple of ways to do this and we've discussed them in the past quite a few times. I'm not saying this is Bill's problem, but it's a possibility to evaluate.