[jluetjen]

Yes 1fastredsc; I think that you might be right. The difference is the CIS system. I suspect that at higher rev's the CIS system acts as a restriction and as a result is pulling a vacuum. If this is true, then the whole equation changes because the speed of sound increases as the air pressure drops.

I don't have an SC nor any car with CIS, nor have I been able to find someone who will try to rig up a test, so there is no way to check my suspicion. If you have a vacuum guage, you can try it by hooking it up with a T connection to an existing vacuum port to the manifold or plenum. Take it out for a drive and run it up to redline a few times and see if any vacuum is detected.

BTW, didn't the early SC's have 34 mm ports rather then 32's? Or was that another typo in BA's book?