Originally Posted by moretraction
Originally Posted by dparker
I pulled my heads and only have .005 clearance valve to piston. I'm thinking about going from a .039 head gasket to a .080 Cometic. I like everything I've heard so far just making sure none of you have any horror stories with these gaskets.......
I asked in my earliar post, How did you come up with .005 valve to piston (ptv) after pulling your heads? Is .005 valve to piston a typo? If not was this a running engine? I know these questions are off topic for the cometic gasket preference question. It looks as though a thicker gasket would not be a very good band aid quench wise, if your cam is degreed wrong you could have .005 and .150 intake and exhaust clearanece or the opposite or???? Your number is not something to throw a gasket at IMO.
I have a 15:1 535BBC that ran a 7.86 at 173.54 at 7100ft of adjusted altitude with a 4:10 gear and 106 circumferance tires. I had just ran a 5.07 at 137 when i killed the car and heard a little poot. I ran a leak down and found that cylinder 3 and 5 had 25%. When I pulled the head off I could see head gasket starting to go, on cylinder 5 and 8 they had the carbon rubbed off the pistons in a 1/8"x1/4" mark, but not down to the aluminum. I put the old gasket back on and retorked the heads checking with clay I had .020 on 5 and 8 and .025 on the rest. I presumed that the rocking of the piston made the difference or maybe those two valves were adjusted a little tighter. Either way I decided to add alittle more clearance so I went with a .040 thicker head gasket. The .005 clearance was what I projected after seeing how the carbon was scuffed by the valve. The .005 difference between the cylinders is from the fact the pistons were fly cut and the edges were rounded for better flame travel. It looks like 2 pistons weren't quite rounded as much as the rest. Making the clearance alittle different. I decided to go with thicker head gaskets instead of grinding on the pistons while they were in the engine.