401 running problem

Well, I am getting ready for the Flint bash, and decided to make my Wildcat 401 automatic run better. So, it has been weak @ 4000 rpm, but fine @ cruising speeds. so I changed the rear end from 3.08:1 to a 3.42. Almost zero noticable difference, still feels way weaker than my 401 Riv. so the engine is suspect. Next. i changed the carb. Carter AFB looks original, wrong ##s, swapped for another. No change.
Yesterday, swpped in a edelbrock 750 (1407), almost new. (ran on a 455 previously). Now there is a big change, feels stronger @ lower rpm's, but @ 4000 there is a huge miss, bad backfiring sounds! Yuk. I decide that I need to look at the ignition.
distributor is @ 0 advance, 42 total no vacuum. Yuk! Changed that. new @ 2.5 advance, 32 total (no vac), factory fine. Still same popping+ problems at WOT. Changed spark plugs, wires, still same problem. Is it the carb or is the carb exposing the weakness that was there before? My next move is to pu another gasket on the carb. I am using a Carter type gasket and metal plate from Carmen. I will put a edelbrock gasket on between the plate and the edelbrock. What else is there that would make this work OK at idle to 2000, then lose power and miss/ backfire at higher RPM's? Coil? Secondaries lean? This engine has been in the car sice I got it. it ran fine, just felt weak. 2" OD dual exhaust, 104 octane gas. Thanks,

 

Flat Cam? Weak valve Springs? Sloppy Timing Chain?

 

My bet is that you either have a stopped up fuel filter or your have a weak fuel pump. Alot of the "reman" fuel pumps you buy at parts stores these days don't flow anywhere near the fuel and pressure they should, although they do supply enough for average driving. I had a friend build a 396 chevy in a truck and spent a whole year taking it back apart several times, changing cams, etc. and in the end all it was was the cheap fuel pump he bought at a local parts store. He got a good AC pump for it and it runs like mad now.

 

Excellent Idea. I will install a new one tonight, let you know.
Thanks you!

I had another car with 2-4bbls on it, it started up but would not run...took the intake off, put the single 4 edelbrck on, still would not run. Then changed the Fuel Pump, and it was fine. Needs the 2-4bbls back on now. So previos experience should have kicked in, but s l o w l y .