Carb issues - Help!

[bluesixtynine]

Here is my sad story...

I ran a Holley projection for years, finally got rid of it mostly because I could'nt keep it tuned. It was always really bad at idle, ran very rich and blew dark smoke. I replaced it with an 1850 Holley I had, and I cannot get it to clear out at idle either.

This carb seems to run best with the circuit screws completely closed, and gets worse as I back them off.

I have checked for vacuum leaks, the intake appears to be well sealed and I cannot figure out why this motor refuses to lean out at idle.

Any ideas out there?

 

[oleguy74]

i have the same trble.mine ran fine for 9 years.my carb is the same except it is the 4160 version.put on another carb today runs fine.sooooooooo i guess it means a total rebuild.something is making them run real lean.i suspect dirt in a passage.

 

[broncnaz]

Other than dirt in the idle sytem. Usually the other biggest cause of this idle problem lies in the secondary throttle plate adjustment. Theres a small set screw under the boss on the pass side of the carb you need to remove the carb to adjust it. You might want to get out your instructions or download a set to get all the adjustment info.
Just had the same issue with a 525 cfm demon carb.

 

[72Quarterhorse]

Not sure but it sounds like it could be a bad power valve.

 

[CDHUNTER]

Please remove the carb and look at the bottom of the valves on the primary side. Do you see any of the transfer slot? If you do then the idle mixture screws aren't going to adjust much for you. Easiest fix is to open the secondaries slightly using the screw that was mentioned earlier. This will let you close the primaries more and isolate the curb idle hole. You should be able to adjust the idle then.

 

[oleguy74]

well there is more to it than that.i did all that to no avail.even closeing primary and setting sec open quite a ways.no help.this was not a gradual thing one day it was fine then not working.i will post when i find whats wrong.