I have a driveability problem with my 48 with a 351W motor. I thought I had it all sorted out last year but yesterday the problems started again..I have an Edelbrock 600 cfm carb (previous history unknown) on this motor. The engine runs fine at speed and the plugs all look good (no fouling) but the engine stumbles when it accelerates off idle.Almost to the point that it stalls. Playing with the timing and also withthe carb mixture needles have not made much of a difference in the problem. Is it time to replace this carb or am I overlooking another problem? I just replaced the points and reset the timing and dwell but the problem still remains. It also smells like the motor is running rich no matter what rods I put in the metering rods in the carb.

 

What Trans? Auto or Manual?

 

I had not touched a carb in 20 years until I bought my 56. It had a stumble or a dead spot on acceleration. Everything was new and checked out. Dad rebuilt the carb and that solved the problem. Its a 272 Y-block and a holly 2100 carb though.

 

What type of intake are you running? Dual or single plane. What temp thermostat are you running? Does it do it always or only when not fully warmed up? I have an edelbrock 600 on my 292 that sat in the box for a couple years, ended up there was still a little petrol in it and it gummed it up. I would take it apart and clean the hell out of it, especially if you don't know it's history. If your changing things and adjusting and it still smells rich at idle it sounds as though somthing in the idle circuit is plugged not letting it get enough oxygen. Good luck, keep us updated.

 

The accelerator pump may be bad. Holleys have an adjustment where you can adjust the amount of fuel that enters the carburetor when you pump the accelerator. I don't know if Edelbrocks have them or not. If so, you could try enriching it. Since you smell gas it might be too rich too. You could try leaning out the adjustment. The carb mixture screws only affects idle.

Vern

 

Problem may be too much carb depending on other engine mods. Yes it's possible to have too much of a good thing. A vaccuum gauge you can watch when driving can tell you a lot about what's happening.

 

I run a 600 cfm Edelbrock on my 351C. I think it is the perfect size for that motor. You can stop messing with the timing. It is the carb.

I too had some stumbling and also a flat spot thru the rpm range. Not being any kind of expert on carbs, I resisted the idea of messing with it. I took it to a "dyno guy" and all he did was screw up the settings. So, I bought an Edelbrock carb calibration kit. It comes with a variety of needle sizes and springs. The instructions are pretty good. It has charts that help explain the effect of various settings. After some fiddling around and trial putts around the neighborhood, I had it running perfectly in an afternoon. Well worth the time and (few) bucks.

BTW, you can stop messing with the adjustment screws. They only affect the idle, but if you richen them up, it will generally richen the mixture while running. Set them and leave them. Instructions for those are in the kit too. You'll be an Edelbrock expert in no time.

 

accelerator pump!!!

 

I agree, thats where I'd start.
good luck
Mike

 

Thanks for your suggestions on the problem. I just found a good deal locally on a new Edelbrock 1406 carb so I think I am going to replace it rather than fix the old one since the old one had alot of tinkering and who knows what else done to it. I'll try the new one out and let you know the results. Thanks again