[Bob Carriere]

Hi Terry

With the Pertronix I had to increase the gap from low 30 to 40 thou...

What kind of plugs are you using??.............. I am using AC C43

Have you tried a vacuum gauge yet..... directly to the manifold....... reading should be steady at 18 + or _ at about 500 rpm.

How slow are you trying to idle the engine...... the 150 rpm variation was it seen on a tachometer?

How does the increase come on and off........ regular intervals or odd interval.... at what RPM those the engine smooth down???

Do you have a see through old style glass gas filter just before the carburator???? do the fuel level vary a lot when idling....... bowl should be about 2/3 to 3/4 full......

The rebuilt Rochester B .... was it the original for that engine and does it have the larger throat opening... any sign of leakage around the carb top cover..... did you check against a flat glass to see if it might be warped.

If you were closer I would suggest swapping carb with mine to see if makes a difference...... currently using a YF carter which is a dream.

The increase in rpm as to be either more gas coming in or an air leak but a leak is a leak...... maybe just lack of fuel..... carb float too low...... anemic fuel pump not sending enough juice at low rpm....

Puzzling......

Cheers