The Stovebolt Site Forums The Shop Area Engine Shop Carb Question

I hear a lot of sucking noise coming from the carburetor on acceleration. The acceleration is poor.

It seems to idle OK. The timing and dwell settings are good. I don’t hear any vacuum leaks in any of the lines.

Before I open it up, could this be the accelerator pump not functioning properly?

Thanks,
Mark

Mark,

You must me running with no air cleaner. Carburetors do make a sucking sound, but using the sound as a diagnostic tool isn't very reliable. A malfunctioning accelerator pump usually won't allow the engine to spin up at all, and is accompanied by bucking and backfiring.

I would check the timing again...this is usually the item that will affect performance the most. Run as much advance as you can without any negative side effects.

Have you set the valves recently? This can affect how snappy the rig is too. If you have a timing light, disconnect your vacuum advance and plug it at the carburetor, rev the engine as you watch the timing marks..your mechanical advance should make the timing marks walk forward as you do this.

Fiddle around, but I wouldn't fixate on the carburetor before I did some timing work, and checked valve lash.

Stuart

I have the air cleaner on. This started when I put on a newer carburetor that I got from a friend. Its actually a Rochester B that doesn't leak and appears to be in good shape.

Is it possible that my timing could have changed much when I switched carbs?

Mark,

Switching carburetors wouldn't change timing, but if the base gasket wasn't installed with the notch to the vacuum sensing port, your power valve could be in a state of constant "dump", which might make your engine feel sluggish.

Stuart

I'll check it. Thanks Stuart.