Quick question... Why stainless valves? Are the stock valves just not strong enough or you need the stainless so they don't melt with the gas... In past experience I've killed my top end by puting too heavy of of valves and valve springs..
Thanks..
I have never seen motor failures due to "too heavy" springs and valves, but I have seen many failures due to light / stock combinations. Immagine as the valve starts to float; the follower starts to jump off the peak of the cam and lands on the back side of the cam face. This impact force quickly causes pitting and brinelling on the cam face which quickly breaks down the entire lobe of the cam.
The other thing that happens is the the follower has a tendency to bounce after it floats and sharply lands on the back side of the cam. This bounce can be enough to shake a keeper out of the groove at the top of the valve. First one keeper drops, and very quickly the second keeper drops, allowing the valve to drop into the chamber causing rapid destruction of the entire motor. Its a misconception that heavy springs wear out cams. Valve float wears out cams.
The other reason for heavy springs is the occasional backfire in the intake. Nitrous unfortunatly causes the occasional backfire, causing pressure on the wrong side of the intake valve. This lifts the valve at the most inoportune time, causing the valve to hit the piston head, bounce back onto the cam, and shake a keeper loose. The result is a dropped valve and total destruction of the motor. Heavier springs can reduce the tendency of "popping" the intake.
Why stainless over Ti? The stainless used for valves has twice the thermal conductivity and three times the stiffness, but unfortunatly weighs almost twice as much. For nitrous motors, its critical to get the heat out of the exhaust valve, and stainless does a slightly better job of that. Also, the stiffness and hardness of the valve helps the valve land truer to the valve seat, thus reducing wear on the valve. Under slow motion photography, you can actually see the valve at high rpm actually bouncing around on the seat trying to center itself as it slams down onto the seat at agressive lifts and durations. Ti valves are just as strong, but the vibrations and harmonics are much tougher on Ti due to the reduced modulus (stiffness). A lot of car guys continue to use Ti with big spring pressure, and it works fine, but the wear is much more rapid.
also u will need to pull some timing
