Piston to Valve clearance

Your probably going to end up fly cutting your pistons to get enough clearance.

Did you Degree it in before checking the clearance?

I'm definitely going to end up fly cutting. Maybe even tomorrow since it's my Birthday!

If .040 is enough for piston to head clearance, why is it not enough for valve to piston? I've never understood the thinking here.
Even if you had valve float, it's likely to happen around max valve lift, and the piston is far away from the valve at that point.
Brian

I would retard the cam 2 degrees and check it before I started taking the heads apart and cutting pistons, much cheaper, easier, and less chance for mistakes

Originally Posted by ou812

If .040 is enough for piston to head clearance, why is it not enough for valve to piston? I've never understood the thinking here.
Even if you had valve float, it's likely to happen around max valve lift, and the piston is far away from the valve at that point.
Brian

I'm no phd in mechanical engineering or metalurgy and don't mean to be an expert by any means. But my limited brain has me thinking along these lines.

Piston to head clearance has 1 variable moving part vs 2 variables on ptv clearance and I'm not aware of pistons having float issues.
On the ptv clearance you have the 2 moving parts that have specific timed events that can have variances not tolerated by each other resulting in crashing into each other along with harmonics the the valves can be influenced by.
I also don't think valve float happens at max lift and would think that it actually rears it's uggly head more when the valve is supposed to be on the seat or on the cams base circle.
Just probably an irrational brain fart I had.

Valve float is when the spring looses control of the valve, this normally occours at max lift and extends to the closing of the valve and sometimes bounces on the seat and yes the valve can and will hit the piston if you do not have enough clearance.