The exhaust valves have a reduced-diameter stem and a tulip-shaped head. This helps flow going out of the chamber. The exhaust valve is nitrided for smoother action and better wear and like the intake valve, we had it WPC treated.
We used Supertech Viton valve seals, Viton is a fluoroelastomer that is very heat and chemical-resistant.
The Achilles heel of the SR20 is its tendency to spit off its rocker arms at high RPM. We started by using new OEM rocker arms that were cryo-treated by CTP cryogenics, to improve strength and wear resistance, then WPC-treated to reduce friction and increase wear resistance.
Next, the SR20 uses one of these guide shims to hold the rocker arm in place combined with a select fit shim on the other valve to adjust the rocker so it sits flat. To hold the rocker more securely, we are using two guide shims on both valves to double the amount of engagement.
We had to modify the rocker, grinding the non-guide shim side to fit in the guide shim.
4 comments
Amazing.
Fantastic article as always! What oil are you going to run with this engine?
15w50
I would pay for content like this.