Motor is a 390..
4bbl edelbrock 600cfm
new points distributor
new plugs, wires, cap and rotor

What it would do before with the holley carb was pretty interesting. you could rev the gas the it would hesitate a second and pop a little, but it would run ok at any steady rpm. If you hit the gas about half throttle really quick and left it, it would just fall on it face and really do nothing.

I put my edelbrock on there. Now the car has little to no off idle transition and revs up really free, but every now and then maybe one out of every 8 revs it will do the half throttle thing where it will just "float" and it just sucks and doesn't really do anything. I also put a new distributor in at the same time as the edelbrock points set at .015.

I can drive it down the road with the edelbrock fine, part throttle feels great, good power, but anything after half throttle it would just not do anything and it felt like i was sitting still. If I hammer it down, it would pick up and start running well after about two seconds, or if i let off it would run well.

What is this flat spot coming from? I know the carb is good as I took it off another running vehicle. Im thinking it was because my old distributor was so sloppy and vacuum advance was just, but that hesitation was still there free revving the car today with new distributor?

The truck did sit for a while, so it may be some potential old gas?

 

Classic accelerator pump problem.

Edelbrock 600 also has more than one hole the accelerator pump rod can go thru at the top. You might also check that adjustment.

 

Currently the rod is set for the most fuel shot as it's on the top hole. I'll try playing with it. Seems odd as it ran great on another vehicle and the truck was doing the same thing with the holley.

 

OK, this suggestion does not exactly fit the symptoms you described as well as the faulty accelerator pump, but, as long as you are playing around with the carb, here's something you can do for fun.

The Edelbrock 600 has two small vacuum line nipples on the front. They are both the same size and are only about three inches apart. One is ported vacuum and one is manifold vacuum. I don't recall which one is which (actually, the manifold vacuum is taken from the engine side of the butterflies), but they can easily be switched. You want to use the manifold vacuum for your distributor vacuum advance. Check this out also.

 

Sounds like carburation troubles to me. Not that OldHarley, can't help you thru this, but there is a section of this forum that deals more specifically with carburators. It is way down towards the bottom of the page in the misc. section.

 

since you had a issue with both carbs I would look at maybe checking for leaks on your manifold maybe and just make sure everything is bolted down good and tight with good gaskets. sounds like its gettin way too much air. also check all vaccum ports on manifold and any trees you might have on the firewall

 

Ok I will check that. Intake gaskets may be needed ill pull a vaccum check and see what im getting at idle.