My buddy has a 69 camaro with a 350. One of the exhaust valves had some unfortunate contact with the piston. I think it was because the cam was a little too big. The guy he bought the car from built the motor himself and he had a .564 lift cam in it with 1.6 rockers. That seems a little big to me. The heads are stock 520 casting with some minor port work, 2.05 1.90 valves, and they've been shaved 15 thousandths. The new cam we ordered is a Comp dual energy 274 with .480 and .490 lift. Will we have any clearence problems with 1.6 rockers?

 

Answer is maybe. 490 lift with 1.5 ratio would increase to 522 w/1.6 ratio. Generally no need to worry about valve to piston clearance with under 500 lift with factory pistons. 500 or more needs to have clearance checked. If pistons have been changed, none of this applies.

To be sure, pop off the valve springs on a cylinder and replace them with light springs. As you rotate the engine, push down on the valves till they tap the pistons. Use a feeler gage to measure between rocker and valve tip at closest point. This is the clearance. Closest point is not necessarily going to be at max lift.

 

The piston chases the exhaust valve as it closes and the intake valve chases the piston down the cylinder. Check 20 degrees on either side of tdc for clearance. The tightest clearance will not be @ tdc. For what its worth I doubt you'll have any trouble.

 

shouldent have no problems im running a 533 555 lift cam in my car.. with 1.5's ... springs help alot tooo