I have new Holley 870 Street Avenger carb on a 540 that doesn't want to return to idle. The linkage is free and moves easily when the engine is off, but when running, it doesn't want to return all the way to idle due to significant binding on the shaft. I have a high torque cam in it and it pulls a ton of vacuum at idle so I'm wondering if that may be what's causing the shaft to bind. Anyone have any experience with these carbs?

Tom

The only info i can give is i had the same problem with my car,would not keep the same rpm's or return to the set idle and i never did figure out why untill one day my cable let go.The little ball the fit's into the gas pedal was pulling itself thru a little at a time which it finally let go.Don't know if this is any help or not but thought i would throw it out there.

Look at how your gasket under the carb is seated - I've had one interfere like that before - but it was hit/miss, not just when the car was on or off.

A 540 with an Avenger 870...the vacuum thru those small venturies is probably drawing the throttle plates open. :D

Make sure your bolts are all drawn down equally. If some are a lot tighter, the base plate will torque a bit and the shaft will bind. It doesnt take much.

Make sure your bolts are all drawn down equally. If some are a lot tighter, the base plate will torque a bit and the shaft will bind. It doesnt take much.

Good advice...I had one that liked to stick, it just needed some lube on the accel pump cam

Are you sure its not weak springs in the distributor, not allowing the mechanical advance to return to zero?

Sure the choke is not hanging up?

I was going to ask the question about the distributor too.

Also, does it have a good throttle return spring?

It's not a timing issue, something is causing the shaft to bind up just off idle. If I force the throttle closed, then it will idle down like it should. As I said earlier this only happens when the engine is running so it's not a distortion issue either. I was just wondering if anyone else running this carb has had similar issues.

Tom

Tom, there really nothing a running motor can due to bind a shaft. Has to be something with the mounting of it. I've had about 3 870 Avengers and all ran top notch.

I can grab all carbs and force the throttle lever down some more, so that may be normal what your doing. Make sure the secondary plates are against the stop. And, they may be open too far. There's a set screw you can back off a bit.

Will the engine die if you back out the idle screw completely?

Where's the throttle spring?

If it's on the bottom pulling rearwards, then try hooking it up to the top, pulling frontwards; directly opposing the throttle cable, instead of both the throttle cable and the spring trying to pull the throttle shaft rearwards.

I can think of one thing a running motor could do. The torque of the motor could cause it to lean and slightly bind the linkage. This is more likely if it is rod-style than cable. And it wouldn't be in the throttle shaft but in the linkage.

Tom, there really nothing a running motor can due to bind a shaft. Has to be something with the mounting of it. I've had about 3 870 Avengers and all ran top notch.



Normally I would agree but I was just out playing with it and the shaft and linkage are loose and operate perfectly until the motor is started. Then it binds up totally and requires a firm push to get it on the idle stop. Much more force than the dual return springs can provide. This happens regardless of the choke position. It also happens when the linkage is disconnected so it's definitely something going on with the carb.

Tom

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I dont like those cheap metal throttle brackets, when working the throttle it pulls against it and the springs are pulling against it.

I have the same issue with dual 650 mechanical Speed Demons on a 6-71 roots blown smallblock. Carbs slam shut perfectly when the motor's not running, but will not fully return to idle when running.
I changed the spring arrangment from rear pull to forward pull, no help, stiffer springs helped some.
Short of using garage door springs I don't think it's fixable....