[classicauto]

Originally Posted by NoDOHC

Update:

Sorry to resurrect this thread, but I have 4400 miles of driving to discuss.

Short story, Brent is 100% correct. The engine does not like high vacuums at lean mixtures at all. I have to run about 12:1 at idle to make it run. My fuel economy is down too (38 mpg instantaneous at 70 to 34 mpg instantaneous at 70, about 29 mpg on a tank). Most of the loss of economy is the fact that at cruising vacuums (~50kPA) I can't go lean of stoic (I was running 16:1 AFR before).

Long story: Too many other factors involved to discuss power (4-port vs. 6-port, bored-out intake runners, heavily modded UIM, etc.) but the detonation resistance is insane.
The engine will not pre-ignite at all. I have never heard it knock (I am still running NA). I advanced my timing until flooring the gas made the engine deccelerate the car and I still heard no knocking noise (70 degrees BTDC).

After those miles (very few actually, in the grand scheme of things) it pulls 70 kPA of Vacuum at idle, makes 100+ psi on all faces and otherwise appears to be in good condition.

Interrestingly enough, the engine makes more torque at 2,000 rpm than the 6-port before it. (It makes a whole lot more torque at 7500.) All in all, I am very pleased with the 4-port NA (my first). Unfortunately, Idle torque is not very good at all, the torque curve doesn't even start until 1500 rpm.

The car is very hard to drive with a stage 2 clutch, 8lb flywheel and no low end torque.

Are you saying the polished rotor faces are helping reduce detonation? And that they are causing you to need to run richer in vaccum?