Installed a new Holley 570 Avenger a week ago.
Set the mixture screws using a vacuum gauge & got a very good high steady vacuum.
Car starts & runs much better now, but I have a very small surging now when running at a steady speed.
Throttle response is great. Just a slow, barely noticable surging at speed.
Before I work on it tomorrow wanted to see what ya'll think it may be.
I would think it's fuel related, but can it be something else?

Mixture too rich?
Something other than the carb (like ignition system)?
I have a new Holley 110gph mech fuel pump also (been on a few months). Is it possible the pressure is too high from that big a pump & causing the surge?
I also went with braided fuel line when I installed the carb & now, because of angles, etc, the fuel line is touching the passenger side valve cover. Could the heat be causing a problem & should I redo that to get it off the cover? But is the top of the valve cover really hot enough to cause a proble?

 

Surging is caused by a lean mixture. Either you have a vacuum leak or you need to richen up your cruise mixture a bit. If you pull a plug and inspect it, I bet it looks nice and white.

I don't think you're going to have a vapor lock problem with braided fuel line. The valve cover doesn't get all that hot, and the braided line should insulate it fairly well. I'd still try to get it away from the valve cover, but I don't think that's your problem.

 

Thanks Tad.

Do you think it's possible that fuel pump has too much pressure? I probably should have gotten the 80gph.

I'll recheck the mixture in the morning.

Because the fuel inlets are angled downward, I had to bend the line at a bad angle. I should have gotten the Holley hard line & I probably will d that soon. But that braided line does look nice so it may have to stay!