• Protip: Profile posts are public! Use Conversations to message other members privately. Everyone can see the content of a profile post.

Tighter Valves for NOS?


Experienced Member
25 September 2000
Tyson's Corner, VA
I was curious if anyone has knowledge of vlave settings that may be more ideal for nitrous. On my recent service, my valves were adjusted. My mechanic said he tightened them more than usual because he knew that I was going to be putting NOS in it. He also said that if I was putting a SC on it, he would leave them looser than normal. Is this a good idea and how do tighter valves it effect the engine for everyday driving in the long run?
I don't know many people that try to tune that way on a street car. The theory is correct, but you still absolutely want to stay within OEM spec.

What he's after is the fact that a tighter valve lash produces effects similar to a bigger cam profile, which gives more duration and overlap. This helps you out in the top end of the power band which is the only place you use nitrous.

With a forced induction setup you want the opposite; excessive overlap robs you of the PSI the pump is trying to put into your cylinders.

But that is just theory. As a practical matter on a street car, I would still recommend simply shooting for adjusting them to spec, possibly towards the tigher end of spec. It is nuts (and very possibly damaging) to try and tune a street car by adjusting valves so they are out of spec.