Looking for advice on engine stumble

[zoomer]

I'm chasing a stumble and hesitation issue with my sbc with edelbrock 1400 .
I have gone though the full set up spring changes adjusted idle screws, moved the pump rod up and down for a bigger\less shot with no change to the issue.

With suggestion from others made changes to timing adjustment and going from ported to full manifold vacuum nothing seems to make a change in the least. One thing I have noticed is a build up of soot or carbon on the metering rod pistons , is this normal or indicative of something going on .

Just looking for some advise on what to check for

Brian

 

[JohnnyBgood]

Years ago I had a similar issue. Turned out the carb was just too big for the motor. If I remember right I was running around a 700 or 750 Holley or so..dropped down to a 600 and was very happy. Might have even changed my intake. Turned out the gas was puddling in the runners. Soot in carb and end of exhaust pipe. Very little difference in performance and way better gas mileage and no hesitation.. my car was a everyday driver so the hesitation was a pain. Food for thought.

 

[zoomer]

Years ago I had a similar issue. Turned out the carb was just too big for the motor. If I remember right I was running around a 700 or 750 Holley or so..dropped down to a 600 and was very happy. Might have even changed my intake. Turned out the gas was puddling in the runners. Soot in carb and end of exhaust pipe. Very little difference in performance and way better gas mileage and no hesitation.. my car was a everyday driver so the hesitation was a pain. Food for thought.

I'm running a little 283 60 over with hump heads ( the 1.94 ones) and the cam has a little lump to it as well . Never entered my mind the carb would be too big. When I first started it a few years ago all seems good then the car went untouched (didn't run) while I worked on everything else , now this .

It pulls good after it stumbles but is very annoying

 

[351CFalcon]

New 350/360HP crate with a 650 Edelbrock also had a stumble.

After constantly adjusting the carb similar to what you've done, did help a bit but did not eliminate the stumble/hesitation, especially at WOT.

Determined Too much gas was the problem.

At first, installed an "inexpensive" simple dial-type fuel pressure regulator which seem to work for a few minutes.

Found out the mechanical fuel pump was putting out too much pressure for for the "inexpensive" regulator as it was pushing the gas through the dial.
The lower the PSI, the more gas came out of the dial.
Subsequent conclusion: too much pressure for the Edelbrock carb.
Edelbrocks don't like high pressure.

Installed a "good" fuel pressure regulator and gauge, set it at 5 PSI, stumble
disappeared.

Might be another area to check.

 

[zoomer]

New 350/360HP crate with a 650 Edelbrock also had a stumble.

After constantly adjusting the carb similar to what you've done, did help a bit but did not eliminate the stumble/hesitation, especially at WOT.

Determined Too much gas was the problem.

At first, installed an "inexpensive" simple dial-type fuel pressure regulator which seem to work for a few minutes.

Found out the mechanical fuel pump was putting out too much pressure for for the "inexpensive" regulator as it was pushing the gas through the dial.
The lower the PSI, the more gas came out of the dial.
Subsequent conclusion: too much pressure for the Edelbrock carb.
Edelbrocks don't like high pressure.

Installed a "good" fuel pressure regulator and gauge, set it at 5 PSI, stumble
disappeared.

Might be another area to check.

Thanks for that tip on pressure .I'm going to go that route next and get a regulator for it