PDA

View Full Version : Carburetor Problems



RebelMtrspts29
04-16-2006, 10:54 PM
I have a different carburetor than I ran last year in the Grand Enduros. Another driver/car used this same carburetor and had no problems. The car idles smooth as can be, and can be slowly brought to high RPM. When the throttle is mashed, the carburetor stumbles, and breaks up, but regains itself a little while after.
This is the same problem I had with the carburetor from last year, which was a computer controlled carburetor. I had removed the computer, and ran it as a mechanical carburetor.
The only vacuum line I have attached is for the power boost. This is a pre-computer Rochester Quadrajet, and there is no choke on this carburetor. I am guessing that it has something to do with a vacuum advance on the distributor??? I don't have any vacuum line on the distributor where the vacuum port is. I'm out of guesses.
Any ideas out there of what could be happening.

art11758
04-17-2006, 09:14 AM
Sounds like you are looking in the right place regarding timing. You swapped out the carb and got the same results, so the problem more than likely isn't there. When you hear the "breaking up" sound, is it coming from the intake or exhaust side? If you are not sure, get some extra ears and eyes, and with the air cleaner off, recreate your problem. Once you determine where the problem is at, add or subtract from your initial timing 10 degrees or so. If the problem changes, you are looking in the right direction. With the fact that the car had computer, which distributer are you using? Some late model distibutors have no mechanical advance and won't work well with out the "smarts" that the computer had. If you have a distributer with mechanical advance, what sort of shape is the mechanism? All beat up, missing springs,egged out pivot holes?? That vacuum advance unit, is there play in that mechanism?? Let me know what you find.

racing#s
04-17-2006, 04:34 PM
I have some stock distributers that I don't need. They came off running, from 8cyl., small block chevys. If you need them holla a message to me.

art11758
04-18-2006, 08:34 AM
Not to rain on the offer of free stuff (I love free stuff), be aware that each distributor has a mechanical advance curve for its intended application. The distributor that came in an 77 Impala with a 305 uses a very different timing curve than one that came in a 80 dually with a 350. Unfortunately externally they all look the same. That timing curve is what the OEM uses to tailor each engine to its application. The specifics of how it is done is rather boring, yet quite important. I can assist somewhat if you want some technical advice or ideas.