Hi to all, I'm new to this site so if I'm taking to long for replying back sorry. Got to find my way around this site...I have a 1973 Plymouth satellite with a 400 Holley two barrel. When I got it it barely ran. I rebuilt the carb and it runs a lot better...new plugs, distributer and wires...the problem I'm have is....is part throttle hesitation or surging. At off idle it does it and its predicable. Idles great, 1/2 to full throttle sets you back in the seat. Timing is set to factory specs. Even disconnected timing advance with hose plugged to see if there was a difference but it was the same. Not sure if it's carb related or electrical. Any help would be greatly appreciated!!!

 

Welcome. First do you know what your initial timing is, I ask because the older engine need more advance with the new gasoline.

Second it sounds like you need more accelerator pump shot or a larger pump shooter nozzle.

 

Thanks for the info......timing is at 10 btdc +- 2.5 degs...accelerator pump adjusted 1/4 top of air horn to bottom of pump shaft........pump adjusting rod im 2nd position from front of carb.......should have mentioned when cruising in L2 rpms about 2900... Then bring rpms down to about 2000 same throttle position as when I get the stumble when accelerating. Find that same throttle position does the same thing....doesn't the accelerator pump work when you suddenly open the throttle.?? Or am I wrong???.. It's like a dead spot that you can find every time you step on the peddle or releasing the peddle....

 

If your at that rpm your out of the pump circuit and into the off idle transfer slot and main circuit. Idle slot restriction could be dirt in that circuit or for both too low of float level or lack of fuel supplied by fuel pump or restricted fuel filter. Lack of fuel delivery would mostly show up at higher rpm under load while accelerating not cruising, which you say is not the case.

I would first do a pump test into a pail to see timed volume, then check float level and needle seat operation or restriction, and of course filter.

Timing sounds ok for a stock cam. What engine are we working on?

I have seen on these older cars that fuel line/tank dirt can cause erratic operation which may not show up with a pump test and the car not moving.

 

I Agree.... Sounds like a pump shot is lazy.. Put some more shot in it...

 

Coronet 500......engine is a 400 with a Holley 2 barrel

 

Do the fuel checks and check your vacuum canister on the distributor to see if it is functioning properly.