i don't know about your head problem. but before you work on your engine check parts availability. i'm rebuilding a 270 for a 31 chevy pickup project i'm working on and can not find reasonable priced pistons. they have to be custom made. then lifters are hard to find reasonable. check bearings, also hard to find. parts are real scarce for these gmc's and when you do find some they cost an arm and leg.
Jay D.
