This is pretty much a unmodified engine , a mild cam and a dual plenum intake , the spark plugs look good , not wet or black , I want to mess with the metering rods to try and cure a off idle stumble , this is a Edelbrock 600 CFM , any suggestions? thanks.

what's the initial? ported or manifold? Is AP tip in immediate/adequate volume? does it do it when fully warmed up? idle vacuum? what springs are in there? float level at 7/16 or slightly lower (richer)? they (the 1406) are lean & I would purchase the strip kit

Start by moving the accelerator pump rod to the hole closest to the air horn in the accelrator pump rocker link.
Doug

Manifold vacuum at idle?

I have the strip kit , it is a model 1311 750 CFM , I looked up the number , the accelerator pump rod is on the position that you mentioned , will check the manifold vacuum , thanks.

and the initial

Ignition first, then fuel. What's the initial timing?

IMO, off-idle stumble is the hallmark of the Edelbrock...running the idle mixture a little over-rich helps more than the other solutions.

I am surprised no one has asked where the primary throttle blades are with respect to the off idle transfer slots. If they are open too far it will create a stumble that will drive one nuts trying to correct the issue.

see if you have a "square" or very close to that

Also begin saving your pennies and dimes for a different carb. At least half the 750 Edelbrocks out there have a pretty incurable stumble. They are famous for this.

When the inevitable post comes along after me saying "I run 10s with my Edelbrock 750" you can sell yours to him. It never fails. During the time that I was buying carburetors from Ebay I noticed that the 750 Edelbrocks were selling for less.

R.

Does yours run 10's with a Holley? Just wondering. Nothing is incurable, just hasn't had the correct fix applied. If the car stumbles it's either rich or lean at the hit. Determine which it is and correct the issue.
Doug

When mine had an off idle stumble, the fuel level was too low in the bowls. Adjusting the floats for more fuel in the bowl fixed the problem.

read this https://board.moparts.org/ubbthreads/ubbt...s-800cfm-14ough
Doug

My mild 440 also had a small stumble that was minimized by adding more initial timing (14 initial, 36 all in) and sitting idle mix to max vacuum. I alsobought the tuning jets and rods, installed a A/F bung and tuned to A/F. Then I swapped the 915 heads and iron intake with Eddy Performer heads and a CH4B manifold. Car starts and runs/pulls hard. But when I stomp on the gas it goes completely flat/lean for a sec, then must get a burst ofgas and goes balls out.. It makes me lurch forward it is so bad. I bought and installed the .043 squirter and a new accelerator pump,but have not tested it yet.

I am ready to buy a Quickfuel 750 and be done with it, but am bummed as I have the finelines stock fuel lines..

Good luck solving yours. Check initial and idle mix with vacuum gauge.

I'm sure you've checked this but is the AP tip in immediate upon the slightest throttle movement? & of good duration and are you on ported for the vac can?

Yeah, my issue may be diff. than the ops. I saw a good stream of fuel before in carb before I changed the AP and squirter. I moved to teh closest hole to airhorn with no help. I have a vacuum secondary casrb. Vacuum is high at idle at 21.

Hopefully the op can lessen his issues with timing and A/F. There are just so many threads all over the internet with this issue and that these carbs aren't meant for modified engines..

I would see what the squirt looks like in your driveway at the offending RPM that it does it out on the road. You wouldn't be under a load but it might show something, it has to be lean for a reason & you'd think it'd be a reasonably easy thing to pin down. my 1406 needed richening (rods/jets) & would bog cuz the choke came off to quick (& I'm talking normal driving

Fury4speed: I am sort of a rookie and wouldn't have been able to tune mine without the A/F meter. I only had a bung on one side fo the exhaust and got a reasonable gauge, but it really helped guide me with the rods/jets. I had it pretty well solved until I switched heads and manifold.. Can you weld a bung in the collector?

It's done all the time. I don't think the bungs cost more than a couple $$.

The O2 sensor on gasoline engines has an 18mm x 1.5 thread same as a spark plug. People have used spark plug "de-foulers" with the externally threaded part cut off.

What my car runs or doesn't run is off the subject. The OP is having problems which sound so familiar, there must be 1000 different posts about this issue. The ironic thing is, most street cars that can run 10s have a 3000+ stall speed torque converter. This means that the engine never sees the condition plaguing the half of 750 Edelbrocks that have the stumble, except maybe on the drive back to the pits.

When I wanted a big Edelbrock I took AndyF's advice and bought an 800.

R.