have original 426 engine - pretty stock

recently worked on timing - got that straightened out and car ran fine all summer

alternator went so replaced that a couple of weeks ago - things were fine

starter motor died - replaced that - things were fine

replaced freight train of a fuel pump with a really nice quite holley (pn 12-125) - car seemed to run fine - but now it is bogging down

so i'll be driving along and notice that it drops in revs a little now and then - and if i get on the accelerator i get a mixed response - so me accerleration...some bogging -

the pump at idle purrs right along - i would think that would be the obvious thing since that is what just changed

but if it weren't, what else might be causing this?

thanks as always to the moparts sleuths!!

How much fuel pressure do you have at the carb? The new pump may be producing too much pressure causing the carb to flood or too little cuasing fuel starvation. Is there any reason you can't just run a stock mechanical pump?

Agree a fuel pressure check is a god idea. A barb "T" on the carb supply line and simple gauge is easy to rig up.

I don't know the original carb... if Holly type, look for 5-7 PSI. If thermoquad/Edelbrock type it wants under 5 psi to prevent overpowering the float/needle. A regulator may be needed.

thx guys

the pump is rated at 7psi max - holley's literature that came with the pump says:

REGULATOR
Not Needed


go figure - i'll rig one up and see what pressure i am getting...

Why arent you running a stock mechanical fuel pump?

It sure sounds like classic fuel starvation like something substantial plugged alot of the flow especially with it still starving that bad on the side streets (low rpm). I'd check the pump for flow then the pickup for restrictions & the filter(s). I'd also go in the carb(s) & take off the clusters (afb/eddys I'm assuming) & flush em with brake kleen

thanks RR - maybe i loosened something and clogged up the works when i changed pumps...i'll start chasing

Yeah you might pull all 8 clusters & give em a good blast & I always replace em in the same recess they came out of. I lube the threads with oil on the carb top mini bolts as they go into aluminum. That'd have to be a hell of a restriction (in the rest of the fuel system) to make it act like that at low speed (assuming it is fuel starvation) so I'd start with the carb. Holler how it turns out

"cluster" is the right word - couldn't get it to start this weekend - didn't have time to do any cleaning though...

Mechanical fuel pumps suck a lot harder than the electric ones do, it sounds like maybe you have a fuel problem with vapor locking I would check the fuel tank pickup filter and sock and all the rubber lines in the fuel system for possible leaking under suction I have seen the stock pickups(in older cars) be plug up inside them with solid guck

OK Cab - I will - thanks