Carb Question

[stix818]

I am currently running a set of dual 1050s on a D-tuned CF motor. My old man is an excellent carb man but still would like to know what you guys think. I just fired the boat up last weekend for the first time. The engine is idling around 2100-2200 and cannot get it to come down. We set the timing at 35 degrees and have the idle mixture screws approximately 2 flats out. The butterflies seem to be completely closed. Thing is running F*CKING great except for the idle (Not ruff just high). We talked about adjusting the idle air bleeds but hoping for some suggestions?
[ September 20, 2002, 09:03 AM: Message edited by: Stix818 ]

[Infomaniac]

What about the secondary butterflies?
It is getting air from somewhere

[MikeF]

Vacuum leak, Is fuel being pulled from the boosters, fuel level too high in bowl.

[stressedout]

Did you make sure the linkage wasn't binding up?
This happens a lot on dual carb motors.

[Jetboatguru]

Vinnie, I had the same problem with mine. I looked everywhere. I finally pulled the manifold and resealed it and that cured it. It was damn annoying because I would rap the throttle and hope it would come down to 1500 but it would stay up around 2300. Also, what stressed out said could be the problem. Good luck

[Hotcrusader76]

Check for vacuum leaks....
Does it have pwr valves?

[stix818]

No powervalves and the float level was not directly checked but after the engine was killed the floats through the site holes looked good (will verify correctly). I broke the linkages loose to the point that I could move them by hand (free from bind) and fired it up and made no difference. I may take the hole damn linkage off and fire it to see if it allows it to come down. All eight butterflies are tied together and they all seem to be closed. I'll check the manifold I guess next (Hate back Tracking). Can't think of were a vaccuum leak may come from (referring to carbs only). Thanks gentleman and if you can think of anything else I would appreciate it. Tony, see you in Phoenix hopefully with this beast. :D

[Hotcrusader76]

Stix818:
No powervalves and the float level was not directly checked but after the engine was killed the floats through the site holes looked good (will verify correctly). I broke the linkages loose to the point that I could move them by hand (free from bind) and fired it up and made no difference. I may take the hole damn linkage off and fire it to see if it allows it to come down. All eight butterflies are tied together and they all seem to be closed. I'll check the manifold I guess next (Hate back Tracking). Can't think of were a vaccuum leak may come from (referring to carbs only). Thanks gentleman and if you can think of anything else I would appreciate it. Tony, see you in Phoenix hopefully with this beast. :D Biggest areas that leaks occur are at the throttle linkages and boosters. You can check your boosters by wiggling them side to side to see if there is alot of play. If they do, a cheap quick fix is to expoxy the top of them where they are staked into the main body.
You can also check to see if the throttle shafts are loose and wobbly. They should be seated firm and rotate with a little smoothness. To repair those requires a bushing job or just a simple teflon ribbon type gasket from Holley. Otherwise consider replaceing the baseplate with a replacement.

[stix818]

Thanks, will check everything out. I think it might be coming from the sheet metal manifold because we had to mill the surface for the new heads (Canfields). Can you guys recall what the EGT should be at approx (Idle)? I'm thinking around 400 degrees.

[T-Bag]

When checking for vaccuum leaks you use either propane or carb cleaner and spray around suspected area and you should get a consistant rpm change when sprayed on the leaky area.

[Mike Oxbig]

T-Bag:
When checking for vaccuum leaks you use either propane or carb cleaner and spray around suspected area and you should get a consistant rpm change when sprayed on the leaky area.Did you just read this straight from "How to Hotrod a Big Block Chevy?"
Great advice :rolleyes:

[stix818]

Great advice. I was trying to figure out a way to do this without taking everything apart. I don't know if you are interested but I will let you know the results.

[396_Z]

I shove a length of hose over the tip of a propane torch so I can pinpoint the exact location of the leak. Just open the propane valve and start sticking the hose end in places where the vacuum leak may be. Simple and works suprisingly well.