Oversized Valves Which Pistons To Use

[Lived4eva]

Hey all,

Looking at running 1mm oversized valves and I realise this can be an issue if you are running greater lift. I have looked at a number of forged pistons and the only off the shelf pistons I can find that specify can be run with 1mm oversized valves is CP pistons. Having said that from the images they don't appear to be scaloped. How much lift and cam timing can you run before 1mm oversized valves makes contact with the piston in a standard engine? Also which pistons are suitable to use with oversized valves.

Thanks

[proengines]

I've run 280/10.8mm lift with 1mm valves without a problem. You need to check at both extremes when you have adjustable gears fitted. The exhaust valve runs closest when the piston is chasing it back onto the seat, worse if you retard the exhaust cam. Whatever the case, always check p/v clearance with high lift/long duration cams, also the clearance between the in/ex valves themselves on the overlap.

[Lived4eva]

Great to know once again thanks for the info .