My old school 340 upgrades and results.

What is everyone's thoughts on spring pressures? My thoughts for a motor turning over 6000 would be 150 seat pressure with 350 open pressure.

It runs well up till it pops. I would think that a flat cam would show up earlier in the rpm range. Leaking valve more so at idle. Granted it has a lopey idle at 1300 rpm so that may hide any problems there.