Poor idle with vacum advance connected

[QUADDAK]

Engine is a 72 400 BB, stock with edelbrock 600 cfm carb.

Any suggestions of what could be causing this problem? I have replaced the distributor with a slighly used one and it does the same thing.

The engine runs fine without the vacum advance connected. Once you connect the vacum advance, the timing goes somewhere (can tell with the light because it is no longer within the normal range). Usually the engine will die. I then adjusted the vacum canister and it now will idle but is loopy. Drive testing it, it runs real good when punched, however when de-accelerating, it will backfire out of the exhast.

Disconnect the vacum advance and it runs fine, just lacks power.

[Dr. Righteous]

Are you sure you have the correct distributor in the engine? A small block distributor will bolt up but it will RETARD instead of advance. It will idle fine but RUN LIKE CRAP when you drive it. ALSO make sure your distrbutor isn't 180* out. (installed backwards) It idle but run like crap. Look close at your timing and eyeball the timing mark. Make sure it steady and not jumping and jerking around. A bad timing chain will jerk your timing all over the place.

[ehostler]

Hook it up to the metered vacuum port of the carb, instead of the straight vacuum port.

I didn't think that an SB distributor could fit in a big block. Doesn't the SB distributor have a gear on the bottom, unlike the B & RB distributors that only have the blade at the end of the saft.

[451boy]

You have something wrong since there shouldn't be any vacuum available at idle for the distributor. Should be zero effect if you have the hoses hooked up correctly. I'll go along with the last guy and suggest that you've hooked up to manifold vacuum and not ported vacuum.

[VetteKilla]

When you hook up your vacuum advance set the idle speed to compenstate for the stalling, then retard the distributor until you get a nice idle. You'll have to play around with the advance to find the sweet spot. I guess you'll have to check to see if your distributor is in fact installed properly.