I put a new cam in my car, the lift is 654in & 652ex. When I turn the motor over the intake valve goes down and back up, but the exhaust valve goes down then stops. But there is still plenty of room in the spring. Iam running AFR 210cc heads with 14cc dished pistons. Does this sound like comp cams cut the lobes wrong on the exhaust side? Nick @ Nu-tek said he hasn't had clearence problems in years!

 

What exactly are you saying when you say that the "exhaust valve goes down but then stops although there's still height left in the spring"?
You're turning it over by hand and there's interference?
Valve to piston contact will occur somewhere along the overlap period.... where both valves are open at the same time and the piston is near TDC. So something's wrong here.
Who installed the cam and was it installed properly. If you did it... then take us through the procedure you used.

-Mindgame

 

did you do a 383?
its possible the crank is hitting the cam-

Or even the rods hitting the block

is the cam "degreed"

 

It is a 396, built by nu-tek motorsports. No I can see the piston where the exhaust valve is hitting it. No the cam is not degreed, Nick said to put it in straight up.

 

silly question-

how can u see the exhuast valve hit the piston

 

Yes, Iam turning the motor over by hand. When the exhaust valve is closing, it stops because the exhaust valve is hitting the piston. When the valve hits the piston, there is still clearence in the valve spring, it is not callasped. Therefore my valve springs are ok. Nick told me to install the cam straight up, so I turned the timing mark on the crank gear straight up, and the timing mark on the cam gear straight down.

 

There is a half moon shape on the eye brow releifs that i can see because of the carbon buildup on the piston.

 

just out of curriousity,
take that rocker out and try it on the other pistons...

 

Just tryed another cylinder, there is no contact. "Don't tell me" what have I looked over this time?

 

1. that one exhuast valve is too big?
2. not timed propperly (my guess)
3. a million other things

i'll let the experts come in here though

 

Any chance that valve stem or pushrod is longer than the others?