weber settings and backfire

[paul cass]

Hey guys
Thanks for the responses. I don't readily have the specs on the cam as I installed it almost 20 years ago. Compression is 10.8 to 1. I run a mixture of 110 leaded and super gas. I have an AOD with a 2900 stall convertor and 4:10 gears. FIA weighs around 2000 pounds. Accelerating is not a problem. It goes like stink! At first when I was adjusting the mixture screws I was able to get everything to work pretty good. No backfires. Then I had to remove the distributor to fix an intake leak and when reinstalled I developed this backfire or popping problem. Not sure why removing and installing the distributor would cause all this. I originally ran a vacuum advance. It is plugged off. I've experimented with the timing ranging from 12 to 24 degrees initial advance. I've installed soft springs for the mechanical part of my distributor and have found that regardless of my initial timing the total advance changes by no more than 15 degrees. I've read that Webers like a lot of advance. Top End and Red Line gave me NO specs on these Webers. Told me I could take them apart if I wanted to know the jets, etc. And I assume these do not have a choke. At least in the diagram one is not shown. So, back to two of my original questions. How far out do I turn the mixture screws and which carb do I start with and then what is the order for the next three?

[Gaz64]

Hi Paul,

My Webers ran best at 3/4 turn out.

If you need to go to 2 turns, your idle jet is lean.

When adjusting mixture strength, doesn't matter which cylinder you start with, or what order you follow from there.

First up, they need to be balanced accurately with a synchrometer.

Then playing with each mixture screw should make that cylinder go rich or lean, the cylinder "goes away", almost like pulling a plug wire.

IDFs can have a starting circuit, cable operated, or come with a blanking plate.

A little disappointing your supplier didn't give you info for your settings.
But that is easy enough for most of it.
Can you look down the venturi and note the number cast into it?
Factory settings for 44 IDF are 36mm venturi, 4.5 aux, 135 main, F11 emulsion tube, 180 air, 50 idle, 50 pump, 50 exhaust (pump inlet valve).

Gary