Q-jet full time vacuum port

[Tom L.]

Just confirming what I'm thinking as I get my carb plumbed. Which port is full time vacuum, the one over the fuel inlet fitting or the one under the bracket for the idle solenoid?

One other thing, for all of you that have C3's with big blocks and power steering, is there an easier way to see the timing tab when checking it? When I get myself in there I can barely get an eye on the timing tab and just feel like either the timing light or my head is going to be eaten by the fan.

Thanks!!

[Mark E.]

Re: Q-jet full time vacuum port

The lower port on the driver's side is for the EEC system, and is ported (its vacuum signal is above the throttle plate, so little/no vacuum at idle).
The higher port on the passenger's side is for vacuum advance, but is connected via the TCS system (also called CEC on some years). It's full manifold vacuum. A common mod is to connect this port directly to the VAC to bypass TCS/CEC.

It's easy to check the type of vacuum signal with a vacuum gauge. A ported signal has little vacuum at idle.

[Mark E.]

Re: Q-jet full time vacuum port

The view of the timing tab could be better on these cars, but there's a direct view of it looking between the water pump housing and idler pulley. It's easier to see with a bright timing light and the TDC mark on the balancer marked with paint.

I slipped on a Chevrolet Performance harmonic balancer cover. It features white on black degreed markings that make it easy to see, plus it's marked through 60 degrees so you can check the advance curve. I've also seen it in Chevy Orange with white markings for a more discrete look.