Idles high.

[Dwaz45]

Heres my issue.......440 motor pretty much oem. edelbrock 1411. Carb was pretty much OK until I started screwing with idle and mixture screws. I cant leave well enough alone. Now it idles at around 850 which is what is was idling at ....however whenever I hit the gas or drive anywhere it stays on high idle about 1500 or 1800 hundred if I tap the gas it drops down to 850 but repeats whenever I hit the gas. Can someone steer me where to start ? It didn't do this before I started messing with it. Im thinkiing its choke related but nothing appears amiss just looking at the linkages. Thank you it's just annoying and my carb knowledge is limited

 

[BeepBeepRR]

First off do you on a vacuum gauge? You will need one to properly tune the carb. You may have a fast idle adjustment out of whack. Watch this video and it should help.

 

[WileERobby]

Check your choke and fast idle cam and linkage.

 

[turbine68rt]

Does your return spring seem to have enough tension at idle?

 

[jimbosride]

As soon as the fast RPM happens.... shut it off and don't touch the pedals and check this

 

[AR67GTX]

As part of the above, once the car is warmed up verify the choke plate is fully open. If not it won’t let the fast idle fully disengage. If not fully open, loosen the screws holding the choke coil cover and rotate the thermo coil cover leaner (probably CCW) until the linkage pulls the choke plate fully open (warm engine).

 

[oldbee]

All the above, but check for a vacuum leak… When’s last time carb was rebuilt?

 

[Dwaz45]

Thank you for all the replies. I'll look at things in the morning. Carb is only 3 years old. New when I had the motor built. Checked for vacuum leaks last week and there weren't any. So I can rule that out at least. I recently pulled the top off and checked and adjusted the float drop and levels

 

[oldbee]

As part of the above, once the car is warmed up verify the choke plate is fully open. If not it won’t let the fast idle fully disengage. If not fully open, loosen the screws holding the choke coil cover and rotate the thermo coil cover leaner (probably CCW) until the linkage pulls the choke plate fully open (warm engine).

Probably not more than one notch. Do it when cold! Choke will be too hot to touch after running. (My 56yo choke has never been touched since new.) Let us know what u find.

 

[Geoff 2]

As well as the fast idle linkage, check:
- pri throttle shaft is not binding
- t/blades are not hitting overhanging base gasket.

Congrats on using a great arb.

 

[Dwaz45]

Ok here's what I have nothing is touching that cam when it's high idling after I goose the throttle and the idle drops still nothing is touching anything. If I touch this linkage on the choke side idle drops. Not the best video but it's what I'm talking about it won't let me load the video sorry

 

[Don Frelier]

Pictures of the return spring Arrangement?

 

[AR67GTX]

As Geoff 2 started to post, could be a worn and sticking/dragging primary throttle shaft. From the plated parts of the carb linkage though, it doesn’t look like a well worn carb. Could also be as simple as needing a stronger return spring.

 

[turbine68rt]

Another thing to check is to make sure your secondaries aren't hanging up and fully close at idle.

 

[AR67GTX]

Another thing to check is to make sure your secondaries aren't hanging up and fully close at idle.

Good point. I’ve seen that heavy gage bent link rod (and associated stop) on the choke side of the carb that links the primary and secondary throttle shafts, get bent out of adjustment somehow and then it can’t pull the secondaries closed.

 

[oldbee]

I think you need to check all adjustments over again, from the beginning. AND, free movement of all pivot places.

 

[Dwaz45]

First off I appreciate all the responses. I love this forum. Almost everything I need to know I've found by reading other posts. Back to mine. It's been a beautiful weekend had the car out everyday plus a show on Saturday. I pulled the carb off to look at the primaries and they are closed as they should be. They're not sticking open. I adjusted my slow idle screw a bit downward and it didn't fix the problem but the high speed idle is only about 1100 now not 1600. And the low idle didn't change much. It's about the same. I'm gonna adjust the high idle screw down a bit and see if that does anything. None of this was a problem till I started messing with stuff. Lol. So I figured all along it was self caused but I just didn't know where to start with fixing it. I'm pretty sure it's the idle screws being not very knowledgeable about this stuff. Just makes it harder.

 

[Dwaz45]

This is how it looks cold before I start or hit the gas and here's the return spring setup

 

[Orig69]

This is how it looks cold before I start or hit the gas and here's the return spring setup

View attachment 1720825

View attachment 1720826

View attachment 1720827

Looking at these pictures with the engine cold the choke plate should be fully open and it's not. To get the choke plate open try to following the instructions in post number 6.

 

[AR67GTX]

Yeah the choke shouldn’t be that far closed unless you pressed down on the pedal enough to allow the cam to slide by the adjustment screw. Once you press part way down on the pedal on a cold engine then the choke should snap mostly closed. But you said you had not touched the throttle which implies the choke plate is sitting mostly the way it was when you last shut off the engine hot - partly closed.