Allowable valve/piston clearances

So what are most guys running as valve/piston clearances in there Blown Alky KB's with alloy rods with an rpm of 9000.

Eli has suggested on my other thread .125" Ex and .090" In.

Any thoughts....

Cheers Ray

 

Those are comfortable numbers. The closer you get the more attention you need to spring pressure. Personally I like to stay minimum .100 on the exhaust.

 

I am running 300lbs of spring on the exhaust valve and not showing any signs of problems.

 

9000 RPM and only 300LBS on the seat. I'm surprised your not killing valves and seats. The valves are probably bouncing on the seats. I've always been real safe with .090" on the intake and .125" on the exhaust. But I run a minimum of 400LBS on the seat. You'll probably gain some power at the upper RPM if you change springs.

 

Ok, I guess I should of been a bit clearer with my first post, I run an early Stage 3 438KB/water heads with a custom ground cam that is a small grind with excellent valve train stability at 9200rpm I have now set it up for 8000rpm but I am allowing for a small over rev:-
113LC, 278/287deg @.050" with .703In/.650Ex lift.

I only have 1.950 installed height so I am using the CC#946 springs, I was told that I should run the exhaust valves with less pressure say 300-320# as they are lighter and no boost on the back of the valve, this way I could cycle my intake springs 340# onto the exhaust as they lost tension?

The combo worked rather well with out any damage what so ever and no sign of bouncing, when we pulled it down to check it out all appeared fine and we only lost 20# over 16 passes and no valve stretching or fretting on the stem from the valve locks etc.

But in my wisdom I decided to install new valve seats and new valves to boot... then my rocker geometry, vlave/piston troubles started as the valves moved back to their origianl position in the chamber.

Ray