My 72 350 4bbl car has developed a spudder when at wide open throttle. It is running a qjet carb. Car idles and runs great under normal driving and when parked revs well. The carb check out fine with a clean filter, good working power piston and accelerator pump. With that being done where do you think the problem lies? Possible sending unit? or fuel pump?

Thank you,
John

 

Vacuum leak, timing, running lean, etc...

 

Checked all even pulled a vacuum line off the carb and ran worse. Timing is spot on.

 

That is not a lot to go on. I have experienced a lot of issues with rough running at WOT and some were fuel issues and others were ignition.

Fuel issues:
fuel pump failure
secondary metering rod fell off hanger
air bleed tube fell out of air horn after a rebuild

Ignition issues:
resistance wire to distributor had corroded terminal
spark plug wire disconnected (idled and ran fine, had a WOT miss/power loss)


These are just some of the things that can cause an issue. If you can provide more info on exactly what is happening and when it happens that may help with diagnosing the problem.

 

Secondaries may be gummed up.

 

I had this issue before I redid my engine bay and replaced the edelbrock carb with the rebuilt qjet. Car really sounds like its starving for fuel. If you let off and hop back on it it goes (most of the time)

 

carb was rebuilt 1 year ago and inspected recently to make sure it wasn't a carb related issue

 

Also did pull some plugs and all are clean and not oily or had gas on them

 

I have experienced something similar to that as well, after doing a long burnout the engine would fall flat at the top of 1st gear, then recover after shifting to 2nd. No problem if I didn't do a long burnout, so it seemed like a fuel starvation issue. Any idea what fuel pump you have on the car?

 

All that carb rebuild really makes me suspect it, actually.

Please describe the specific WOT activity. I had plugged secondaries and mine would go like a bat out of hell, but would not go above 65 mph on the road, even to cruise. It would surge.

When you are flooring it, are you at highway speed, or just launching from a light, or doing 30 or so? Secondaries are not involved in flooring it at lower speeds, even though the throttle is open, the air valves are not.

Does it surge on you, like if you were to punch the gas every second, or does it really fall on its face for many seconds? I think an inadequate fuel pump and an empty bowl makes you fall off for more than just a second, but others will have to confirm that.

 

Fuel pump sock?

 

Cracked rubber lines between the tank and metal fuel line or metal line to pump.

 

Secondary air valve door setting. Stock engine or modified?

 

Bad plug wires failing under load