Piston/valve clearance

Paul V8 · Post by **Paul V8** » Tue Feb 23, 2010 9:15 pm

Hello, does anyone know what sort of clearance I should have between pistons and valves. I'm using a crower 50232 cam in a 4 litre. I have contact and need the pistons pocketing.

mgbv8 · Post by **mgbv8** » Tue Feb 23, 2010 9:31 pm

I seem to remember that I needed around 70 thou clearance. But I'm probably wrong as usual???

Boosted LS1 · Post by **Boosted LS1** » Tue Feb 23, 2010 10:19 pm

it's the exhaust that's important as it's opening when the piston is on the upstroke. I agree with the above, you need .060" or thereabouts.

kiwicar · Post by **kiwicar** » Wed Feb 24, 2010 11:06 am

Just to add another vote for 60 thou minimum.
Mike

jefferybond · Post by **jefferybond** » Wed Feb 24, 2010 11:30 am

Boosted LS1 wrote:it's the exhaust that's important as it's opening when the piston is on the upstroke. I agree with the above, you need .060" or thereabouts.

Exhaust will begin to open on the downstroke, before BDC and close a short time after TDC.

The intake will be opening just before the piston reaches TDC, and since the intake valve is larger, it might need larger cutouts too.

Jeff