Help with Edelbrock carb

Working on my 1988 Blazer TBI to carb swap (125k miles on stock engine) and am having some issues with the Edelbrock carb. I'm sticking with this carb so please no "junk it and get a holley" comments.


Changes to vehicle:
New summit 0032 cam, 204/.427 single pattern, 110 LS
New timing chain
New Hei dist, wires, Rt45 plugs, stock timing, no mods to dist, base timing set to 8 degrees, 17" of vacuum.
New mech fuel pump and regulator set to 5 psi, all new fuel lines.
Used Weiand Stealth intake with 1/2", 4 hole wood spacer as I had some fuel boiling issues.
Edelbrock Thunder AVS carb. I bought this used 2 yrs ago and it was supposedly newly rebuilt. Its been sitting in my garage since purchased and just put on this week. Carb looked pristine so I believe it was rebuilt and had not had any fuel run through it since the rebuild. Carb runs great for the most part but I have the issue listed below.


Issue:
On the passenger side of the carb, the idle mixture screw has no effect on idle speed or vacuum. Driver side does change everything as it should including killing the engine when the screw is completely removed. Spraying ChemTool/carb cleaner into the carb throat causes the engine to slow down but spraying the cleaner into the passenger side mixture screw hole causes the speed to increase.

I also sprayed all around the carb, vac hoses, intake mounting areas with no vacuum leaks found.

Any ideas on why the mixture screw doesn't change the carb like it should? Or should I just cut to the chase and pull it and put a kit in it?

Sounds like a clogged idle circuit. Remove both idle air screws and apply 40 psi regulated air to the screw holes. You may want to remove the top of the carb and make sure the bowls are clean before trying again. Lastly use a quality fuel filter like a WIX paper element fuel filter. Those cleanable screen filters let too much junk through. Once you fire it up you'll likely have to adjust the idle air and base idle screws all over again.

crazy4offroad said:

Sounds like a clogged idle circuit. Remove both idle air screws and apply 40 psi regulated air to the screw holes. You may want to remove the top of the carb and make sure the bowls are clean before trying again. Lastly use a quality fuel filter like a WIX paper element fuel filter. Those cleanable screen filters let too much junk through. Once you fire it up you'll likely have to adjust the idle air and base idle screws all over again.

Click to expand...

Will do, thanks for the tip!