Checked a 250 today. Covered an OEM 307 piston top with bondo to create a true zero deck flat top with no valve relief. It was a STD piston in a .030 bore so I slipped a shim in to keep it square in the bore. .040 head gasket. Comp 260 hydraulic flat tappet cam installed at 3 degrees advanced. Head was 1184 casting with 1.89 intake and 1.6 exhaust valves. Stock pushrods and rockers, solid lifters. The minimum clearance I found was .240 inch on the intake. Exhaust clearance was more like .350.
Sent some photos of the operation to Tom.
