Re: 1940 356 engine problem

Posted by Owen_Dyneto On 2013/2/2 23:43:43

I'm not sure of your 0.250" measurement but the cam lift on the 356 engine is 0.340". Since you didn't have the problem before replacing theheadgasket, I'd say the milling of the head the final 0.012" was the proverbial straw that broke the camel's back - speaking just for myself I NEVER mill a head unless absolutely essential. I'd say it's just about impossible for any resonable oil pressure to counteract the pressure exerted by the valve spring unless the spring was broken or unbelieveably weak - not really likely but worth investigating if nothing else but to eliminate it. Since you've got to replace one valve, I'd do a quick valve job, perhaps just hand-lapping if the surfaces look good. And thereafter check the lifter reserve take up clearance (0.030 to 0.070 between the valve stem and the gauge block inserted into the cam follower. And then I'd do the head test fit with putty or clay on the valve heads to absolutely establish if you have adequate clearance.

Just remember when shopping for another head, it may prove to be no better than the one you have. Depending on what clearance or interference you find, you might consider the earlier suggestion of grinding a bit of relief into the combustion chamber after some additional measurements.

PS - I assume a typo when you said the compressed head gasket was 0.004"? should be more like 0.040".