Originally Posted by cobalt327
The key to making the thumpr cam behave is more initial timing. I'd start w/about 22 degrees BTDC and work up or down as needed from there.
Vortec heads only need 32 degrees total timing, not counting vacuum advance. More on setting up the timing correctly is linked to below. Until you get the timing sorted out, you're going to have a hard time w/idle quality, nozzle drip, off idle response, etc.
Use a vacuum advance limited to 10 degrees, use ported vacuum for it.
If you find you're still having a problem getting a balance between idle quality and initial advance (advance isn't helping enough), you may need to add idle bypass air.
Not all Q-jets have a threaded rear port for a power brake booster. Use a manifold port if yours doesn't. The front large vacuum port is for the PCV valve.
Carb vacuum port ID
You most likely do need more stall, but sort the timing out first, then see what you need if anything.
This truck is strictly an off road truck it will probably never come out of 1st and or 2nd gear... Fuel milagr doesn't bother me... So can I completely get rid of or plug off vacuum advance? Will this help the truck from dying going into gear? I'm sorry I'm kinda virgin to the tuning part of things. Thanks again