I assume that if you advance your cam by 4 degrees that you should back your timing off by 4. Or is there a difference??
My truck has not been zero decked, & during my valve to piston clay check during the ecz-g install last month i measured almost .090 quench between the head & piston outside the combustion chamber with an old head gasket torqued to spec, measured at .045 with digital callipers.
I thought that engines with too much quench would tolerate less advance?
I am running 25 at a fast idle of 950, & total timing of 38 @ 3500 -4000 with about 5 degrees of vacuum pot.