Minimum valve to piston clearance?

[Jeffrey Osstyn]

I'm with Dave on guide clearance my cylinder head guy tells me that is the most common mistake he sees on problem heads,they are setup where the valves move nice and smooth with minimal wiggle in the guide and as soon as you put some heat in them they don't want to move.He says there's a fine line between too much and too little.Also since it is limited to 1 valve you may have been unlucky enough to have a new spring fail right out of the gate,wouldn't be the first time.

O.K. So what is a good exhaust valve guide to valve stem clearance?

 

[Don Jacks]

.0015-.002 Jeffrey

 

[Jeffrey Osstyn]

.0015-.002 Jeffrey

I would agree on that for the intake, but you run the exhaust valve the same?

 

[Don Jacks]

I run the intake .001-.0015,the exhaust about.00075 -.001 looser.Haven't had any issues yet.

 

[La Hot Rods]

I think the 690 heads that came off the 12.30s 409 had about a good 1/4 inch play.

 

[El Rat]

Swap the “offending “ rocker arm with a well behaved rocker.