Re: Darrin's 1954 Super Clipper Club Sedan

Posted by Owen_Dyneto On 2011/4/10 16:43:21

Modern engines with high compression, overhead cams, and very thin shim-type head gaskets require a high degree of flatness between the head and block. Older flathead engines with compressible headgaskets are much more tolerant; certainly heads out of true by 0.015 or so don't require machining and I'm sure some will say the tolerance is even greater. Needless surface grinding a head has sent many to the trash bin and you're off shopping for another.

Your valves are mounted at a slight angle to the bore center. The first thing that will happen with insufficient clearance is that one or more of the valves will suffer bent heads with consequent loss of compression. If the situation continues, the lifters, cam followers, and the camshaft itself could be damaged if the bending of the valve head doesn't provide enough relief. I've seen all of those; it's also possible the head could be cracked though I've not seen that.

PS - I don't mean to sound like the prophet of doom. If the head was never surfaced before and they only took off 0.015" or so, it will almost certainly be OK. If it were mine and I was indoubt about it, for the cost of a headgasket I'd take it apart and check.