The folks on this forum have helped me in the past, hoping I can get more help. The previous owners removed the computer, swapped the Quadrajet for an Edelbrock carb and retained the original distrubutor. I rebuilt the carb but still having issues with a rough idle and stumble off idle. The the engine runs strong above idle. No smoke, no significant oil leaks etc. I suspect that timing is an issue as well as the transition from idle to low speed. I'm wondering if a switch from the existing distributor (non-vacuum advance) to one with pre-electronic carb vacuum advance might help with low speed performance. In addition my tach bounces all over the map above 2000 RPM; suspect the distributor interference. I've seen adds for a filter that is supposed to help the tach but not sure how to wire it in.

So, questions: Will a 1980 distributor plug in? The 1981 distributor only has a small plug with a pink wire and white wire that plugs in under the distributor cap. Does the filter connect to the white tach wire and ground or?? Should I continue to battle with the Edelbrock (on an aluminum adapter on the intake manifold) or swap for a pre-electronic Quadrajet?

I plumbed in a fuel pressure regulator set at about 5 psi and the lower fuel pressure to the Edelbrock needle and seats seem to be preventing the fuel overflow I had previously.

 

Is the distributor a chevy vacuum advance HEI without the later ecm wiring and module or other?

Does this happen after the engine warms up?
have you pulled ignition wires off to see if one or two cylinders dont change?

 

If you still have the EGR valve on the engine, the pintle might no be fully seated at idle, and may be opening prematurely on initial acceleration. Remove and plug vacuum line to EGR and drive to see if acceleration stumble is gone. Vacuum may be holding pintle open at idle which may solve idle roughness. If no issue is resolved or if only one is resolved. then remove EGR and inspect to see if pintle is stuck open. If so, replace EGR or purchase an EGR block off plate.

 

Get rid of the Edelbrockcarb and find a good rebuilt pre computer Q-Jet. Call Phil at Custom Rebuilt Carb in NJ and tell him what you want to do. He should be able to supply you with a high quality professionally rebuilt Q-jet set up for your application.

https://customrebuiltcarburetors.com/

 

Thanks for the reply Dave. The distributor is the original HEI without vacuum advance. With the computer gone I only have mechanical advance. I think a distributor with vacuum advance would help with performance and mileage. Just not sure if it would be a simple plug and play.

Did a compression check and all cylinders are within about 15% of each other, around 120 psi +/-
Haven't tried pulling wires but will this weekend. Weather has not been cooperative with temps in the teens, well below normal for northern Alabama.

 

The '81 engine control system was a one-year-only setup with 'special' distributor, carb, O2 sensor, TPS, wiring harness and an early vintage ECM. All of those '81 components from that year needs to be in place for it to work correctly
OR
the carb and distributor BOTH need to be swapped out for earlier vintage units with or without electronic ignition system. If the distributor you now have is original to the car, it won't work correctly with "other" stuff.

 

OK, Yes , a 75 - 80 distributor will plug right in.
a carburetor from a earlier car will also fit the stock intake.
A completely different gen 1 small block can be dropped in.
Lots can be done. Your car, your budget.

 

Distributor is the original OE HEI distributor without vacuum advance. Stumble off idle happens hot or cold.
Thursday night I barely got it home running very rough the whole way, like a plugged fuel filter or failing fuel pump. Turned out there was a tubular shaped screen lying crosswise in the fuel inlet of the carburetor. Where that came from I have no idea but once I removed it with a pair of needle nose pliers and hooked the fuel line up again the engine cranked right up and settled to a smooth idle. Still has the stumble off idle but idles smoothly and once past the stumble it runs fine. I suspect something is wrong in the transition circuit, debris or??

 

The ofiginal 1981 distributor will not work properly when engine has regular carb on it. Good luck with your refurb....

 

I have a 1981,and I also got rid of the computer,I have a edelbrock carburetor and replaced the distributor with one from summit,you can’t use the stock distributor without the computer.I have no issues with mine.good luck.