91 Octane in a 340?
Rusty ! I thought that your toilets run backwards!
My 410 has what I thought to be 11to1 compression. It has SRP forged pistons with a 28 thou head gasket and 61 cc trickflow heads. I measured it for comp pressure with a elcheapo Compression guage and it said it was 150 psi . I purchased a Snap On guage and it showed 205 psi , which is more likely. Irun my car on premium grade fuel and it doesn't Ping!!