Thread: Piston hitting valves?

Hi All

yesterday i changed my intake cam timing on brian crower stage 3's from +2 to +3. Now it runs fine up till about 5000rpm where there seems to be some tapping sound. As soon as i hear the sound i change gears and it stops.

Could the Valves now be hitting the pistons @ 5000rpm?

Im running stock 9.5:1 pistons, it was fine at +2 even at 8000rpm.

Im running aftermarket ecu with advanced timing maps, could it now be pinging?

What springs and retainers are you running with those cams?

Im running the brian crower springs & Tomei Rocker arm stoppers.

I would think if the valves were hitting the pistons enough that you could hear it, it would certanly bend them ....sounds more like a valve clearance issue or a pinging or ?

I always though that either they would always hit or never hit. I didn't think RPM factored into it (VVL excluded). Someone correct me if I'm wrong.

Back the timing off right where you hear the noise 5*, pull a couple degrees out above 5k as well and see if it's still there. Add it back as the engine allows. You've increased the effective compression ratio by advancing the intake cam.

Ive just done exactly that, will let you know how it goes hopefully thats the problem.

I thought it could have been the valve hitting the piston due to rod stretch or something.

Fingers Crossed.

It was pinging, all working great now.

Nice, how's it feel?

I have similar question.. my friend is going run BC st3g cams on stock cam timing + SR kit in 10:1 CR SR20DE.. is it safe? No piston hitting? Thanks