L31MaxExpress
I'm Awesome
It is spring pressure that is the issue. I found valve float show up at 4,500 in the L31 in my Express once. Upgraded to the LS6 springs on Comp 787 retainers and I could rev cleanly to 6,000 rpm after without the dyno chart looking like a 7.0 earthquake at high rpm. The difference was over 28 rwhp at 5,200 and climbed past 40 rwhp at 5,500. Engine was pulled to the stock 5,600 rpm fuel shut-off at the time. The OE springs had such bad harmonics it lost 30 rwhp between 5,150 and 5,350 rpm. The stock springs are only like 70# on the seat new and mine were down to 55# when tested.