Vacuum

I used to wonder why there wasn't more agreement on which is best. Much conflicting advice.

I think that with higher compression motors you want it on ported, but many times a low compression motor will respond really well connected to manifold vacuum. I've been running a 8.5 compression 340 and have experimented a lot, and definitely think the motor does better on manifold.

I think this is because with lower the compression and at lower rpm's the motor wants more advance so there's more time to burn the fuel, and the manifold vacuum helps with this, whereas hooked to ported the vacuum drops off at idle.