Hi BadSS - Just thinking that a roller cam may behave very differently from flat-tappet cam. A roller side-loads the cam lobe (= exerts a disruptive torque) as the roller rides up and down the side ramps. A flat tappet only loads the cam as a function of changing friction. Somewhere I'm sure I've got a book (Blevins?) that I can look up to quickly calculate the torsional resonance... 8,500 rpm = 4,250 cam rpm, and with 16 lobes (17 counting the fuel pump lobe,) with 34 total side ramps, we are exciting the cam at roughly 1.3kHz. I need to see how close that is to torsional resonance.

BUT anyway before I go off the deep end - Brent, given BadSS's good experience, I see no cause for alarm, thankfully.

Last edited by MAP; 10/13/21 06:33 AM.