Valvetrain geometry question

I'm turning my circle track engine into one for the street. When it was built, we tried to get the most compression out of a flat top piston setup. It's got 0 deck height, 50cc heads, and I think .010 steel shims for gaskets. I want to lower the compression by getting the thickest head gaskets I can find for an SBC. My question is: As the head rises, the distance between the pushrod tip and the rocker arm will also increase. I would assume this means the valve is going to take longer to open and shut. How much is this going to affect a street motor versus one that was built to turn 7 grand down a straight a way?

 

call your engine builder and see what he has for longer pushrods. All the racers i know have boxes of diffrent legnth push rods for all the diffrent changes there motors have gone threw.

 

Well if you are changing head gaskets only, you are not going to have any problems. Most readily available head gaskets are in the area of 30 to 40 thousandths thick. So really you are only raising the heads 20 to 30 thousandths. Thats no big deal. If you are going to put on some super thick copper head gaskets you are more than likely have more problems than pushrod length. You will probably have a detonation issue because of your large quench area.

 

NO! That has NO affect on when the valve opens. ASSUMING the pushrod length was correct, i don't think there's a head gasket on the planet thick enough to mandate a longer pushrod. If you're worried about it, remove a rocker (after the gasket change), smear a Sharpie across the tip of the valve, replace the rocker, rotate the motor a couple times and see how close to the center of the valve the rocker has wiped the ink. PS- If the compression was THAT high, consider a little chamber work while the heads are off to lower compression

 

Shouldn't be a problem but check anyway.

 

If this is a race motor, does it have an adjustable valvetrain? It should more than take care of thicker headgaskets. You want around .040" quench. Since you said you have flattops with zero deck, that means you want a .040" compressed headgasket. What compression would that give you and are your heads iron or aluminum?