Idle speed too high.

[Kent mosby]

I have a 512 bb with a Holley 0-80508SA 750CFM ALUMINUM Vacuum Secondary Carb on a run stand. We had it broken in and running well but it had a small oil leak. I fixed the main seal and ran it for 30 minutes today to test for any leaks, none!!!!. However the idle was at 1250 rpms or so. It previously was at 800 or so with 12.5 in hg. I have the idle set screw completely backed out. It has set for about 5 months without being started. Any thoughts, mixture, timing, fuel? Nothing that I know was changed. Did not check the timing or vacuum just yet. I wanted some guidance before changing too much.

Thanks for any help.

 

[MOPAROFFICIAL]

Choke?

 

[Kent mosby]

Choke is electric and wide open

 

[fishmens67]

Check the ignition timing, may be too far advanced. most likely.

 

[67Dart273]

First thing to do FIRST VERY FIRST is get the timing right. PERIOD!!!

Then look for vacuum leaks. Use water "spritz" from a pump squirt bottle, and or get a length of hose up to your ear and listen for air leaks. Don't forget to actually CHECK that all 4 barrels are closing

 

[Lil Demon]

Holley are notorious for coming with secondary throttle plates too far open. I’ve made it a habit to check them on every carburetor I work on cause it avoids a lot of tuning issues. Also verify choke linkage isn’t missing a bushing behind the throttle lever, I’ve seen that before where it shifts slightly and causes lever to stay slightly open despite choke being wide open