SB

iTrader: (1)

Well, I believe the 572's use Crane cams,,,so....the lifter will probably be Crane, which will save my azz......LOL.

Thanks ! :wink:

MILD THUNDER

iTrader: (3)

Why is it that everyone always just talks about "seat" pressure. You can have a spring that has 175lbs on the seat, and 450 over the nose, or 350 over the nose. Which one you think will be harder on the lifter? Controlling the lifter while its going over those nose of the lobe, is a very important scenerio, and shouldnt be overlooked. When you get into higher revving, higher spring pressures, the material of the lifter body, as well as the internal valving, becomes important. in other words, I would not recommend running a 450+ over the nose spring with the lifter than comes in a 454 MPI engine.

Rage

Is that the GM17120061 lifter for the Gen VI 454 and 502 engine that: "NOTE: These lifters allow more oil to the rocker arms than the late-model truck roller lifters."

If yes do they then experience bleed down above the 450 # spring pressure that you mention or something else?

Separate question...are light chatter marks on the lobe nose a sign of insufficient spring load at max lift to control the valve train?

Rage

Attached is GM spec sheet for the ZZ572/620 engine with the GM17120060 lifter. With seat load of 197# at 1.950", spring rate of 480#/inch and 0.63" lift cam translates to 499# over the nose and 6000 rpm. That should qualify as a very robust lifter. A remaining parameter is the max lobe rise rate (cam jerk) with this cam and as long as the max lobe rise rate of the application is the same or less than this cam these loads should be good. The durations of the ZZ572 cam are rather large.