Carb Backfire - Too Rich or Too Lean? Reco. on jet/rod for Edelbrock 1405

[Corellian Corvette]

I have an edelbrock 1405 of unknown origin on my 383 4bbl.

I'm getting a backfire through the carb at higher RPM when I quickly let the throttle snap back.

I don't think it's ignition, since I've replaced all the plugs, and have brand new MSD wires, MSD Blaster II coil, and MSD billitt ready-to-run.

The carb has black deposits on everything, so there is something wrong with the carb is my guess.

I'm tearing it down tonight to figure out what Jets/Rods i'm running, but I'm hoping to get some suggestions on the best jet/rod setup for my 383.

Also - could an exhaust leak cause backfire? I'm pretty sure there are some bad welds in my exhaust system, too. Manifold looks good and all the bolts have been tourqued.

So, to recap.

1. Is Backfire generally a symptom of too rich or too lean?
2. Any recomendations for jet/rods for an Edelbrock 1405 on a 383 car.
3. Could minor exhaust leaks be contributing to the problem?

Thanks!

[TylerCharger69]

backfiring  through the carb??   Sounds like either your loading up due to misadjusted float levels  or an ignition problem.   I have the same set up.....383  w/Eddy 1405  and I have no problems.    Are you putting out black smoke when you rev it?   When I got my carb  out of the box,  I came to realize that I had to adjust the float levels  since they were too high.  But other than that....it works fine,  but mine was new in the box.

[Corellian Corvette]

Thanks. I took the carb apart last night. All the parts in the venturi were covered in black soot. The float level was set to factory specs, but the float DROP was like 2 in!! (actually I'm not sure what the symptoms of too low a float drop are)

Also, the carb out of the box is jetted MUCH richer than the stock carb. Like 150% richer! I looked in the Eddy book and jetted it down quite a bit to get it about 10% richer on the idle side and about 25% richer on the power side than the stock carb.

Unfortunaty, my radiator is shot and I'm getting if fixed over the weekend so I can't test the new setup.