Leakdown test tells it all, I rebuild;ld my 1000 hp blown 540 every 100-120 hours BUT I am running 13-14 psi of boost, I find leakdown starting to get where it needs to be re-rung plus bearings, lifters and valve springs at my interval but again, a much higher amount of stress and wear, fwiw, Smitty

Ok just did a compression test on one motor and it wasn't good. One bank was 80 , 90 110 and 120. Other bank was all 150. Will leaky valves do that ?