When I pull the vacuum adavance line
to time it the engine stalls, and must
raise the idle to keep it going. Is this
the correct behavior? It seems to run OK
with the vacuum advance connected and the
idle jumps right back up to 700 rpm.
It started doing this as soon as I installed
a new GM HEI distributor. The vacuum advance
diaphram was broken on the old HEI for years.
Thanks.

'67 Camaro
Muncie 4sp
350
GM HEI
Rochester

Sounds like you have the vac advance connected to maifold vacuum instead of ported vacuum.

Not sure what vac port is which on a Q-jet, but with a Holley the ported vacuum is the one that comes off the passenger side of the front metering block.

If you like your advance hooked up to a manifold source (adds timing at idle and part throttle)than don't worry, just leave it that way -- the RPM drop you are seeing is normal. If you want to hook it up to a ported source (doesn't add any timing at idle only part throttle) you will have to turn the idle screw up until it idles where you want it to.

I personally prefer ported vacuum advance with a mild to moderate camshaft. Manifold vacuum advance works good with radical cams -- helps the engine idle better.

Your mechanical timing should not start before 900 rpm so adjust the idle up so it's just under 900 before you disconnect the vacuum advance an plug it's source and then go ahead and check and set your timing. Hook it all back up and adjust the idle back down...

You may want to base line the dist to see how much mechanical advance is built into it and also how much vacuum advance is being pulled in. Some of the smog vintage hei's really have a lot of vacuum advance. Check your initial with the vacuum hooked as you now have it and subtract the initial without the vacuum hooked up from it to see what is in the vacuum can...

If the engine is warmed up pulling the advance will cause the idle to drop. You'll have to raise the idle before hand up a bit.. pull and block the port. Reset timing to correct * and adjust idle down to correct level.. Reconnect advance and watch idle climb up a bit and level out. You'll notice the idle drop when placing car into gear.

Thanks Gents. After looking at a fine
diagram of the Edelbrock Q-Jet, my vacuum
advance is connected to the "Diverter Port"
(passenger side). Something tells me it
should be connected to the "Distributor Port"
(low-front). Any idea what a "Diverter Port"
may be?

Divertor port is for the smog system.