Paul57

I have Comp 918 springs (.625 max lift recommended) on PRC Stage 1 LS6 heads (stock valves) and a .598/.600 lift cam. Should I be shimming the valve springs?? Coil bind is at 1.1. Should I be adding .045 shims??

01ssreda4

iTrader: (96)

We need to know your actual installed height....

Paul57

stock...1.8

01ssreda4

iTrader: (96)

They don't all measure out to 1.80000. You need to measure it.

Paul57

OK...the shop said they are 1.79.

01ssreda4

iTrader: (96)

Ok so you need to plug that into your formula and figure out coil bind, and how far you want to be away from coil bind at max lift, then you will come up with your shim thickness.

ZeeOSix

What's the advantage of running the springs so close to coil bind? Installed height of 1.790" is well within specs.

01ssreda4

iTrader: (96)

Running at say .060 away from coilbind gives maximum valve control at higher rpms. It keeps the valves from bouncing around on the seat and/or floating with aggressive cam lobes.

driver56

I've read that a NASCAR trick is to run the springs very close to coil bind as it leaves less room between coils for oscillation to happen. Basically the spring can't float or lose control because there's no room left for bounce.