C2 Holley fast idle adjustment

[brumbach]

I've recently rebuilt my 6140 holley. List number 3367, has a remote choke thermostat. I need to raise the fast idle. How is this done? Thanks -- Bill

 

[WayneC]

As I recall... if you look at the choke linkage, I think there is a rotating fast idle cam (formed plastic piece) positioned in it's arc of swing by the link coming up from the choke coil. With the engine cold, open the throttle linkage on the driver side while looking at the choke linkage on the passenger side. You should see the fast idle cam swing into a position where the top step of the cam is engaged by a fast idle lever when you release the throttle linkage... ie, the lever sits against the cam, and the lever is connected to the throttle linkage, so the lever moves whenever you move the throttle linkage, and the cam swings to a position that prevents the throttle linkage from rotating fully closed (to the idle speed stop screw).

1. make sure the fast idle cam rotates to a position that allows the fast idle lever to contact the cam's top step

2. bend the fast idle lever so that it holds the throttle further open on that top cam step.

As the engine warms up and you operate the throttle while driving, the thermostat link causes the fast idle cam to rotate to where the fast idle lever progressively contacts lower steps on the cam (when you take your foot off the throttle) until finally, when the engine is fully warm, the cam swings out of the way and the fast idle lever doesn't contact the cam at all, so the engine idle speed is then governed by the (normal) throttle idle stop screw setting.

 

[IH2LOSE]

As I recall... if you look at the choke linkage, I think there is a rotating fast idle cam (formed plastic piece) positioned in it's arc of swing by the link coming up from the choke coil. With the engine cold, open the throttle linkage on the driver side while looking at the choke linkage on the passenger side. You should see the fast idle cam swing into a position where the top step of the cam is engaged by a fast idle lever when you release the throttle linkage... ie, the lever sits against the cam, and the lever is connected to the throttle linkage, so the lever moves whenever you move the throttle linkage, and the cam swings to a position that prevents the throttle linkage from rotating fully closed (to the idle speed stop screw).

1. make sure the fast idle cam rotates to a position that allows the fast idle lever to contact the cam's top step

2. bend the fast idle lever so that it holds the throttle further open on that top cam step.

As the engine warms up and you operate the throttle while driving, the thermostat link causes the fast idle cam to rotate to where the fast idle lever progressively contacts lower steps on the cam (when you take your foot off the throttle) until finally, when the engine is fully warm, the cam swings out of the way and the fast idle lever doesn't contact the cam at all, so the engine idle speed is then governed by the (normal) throttle idle stop screw setting.

Brumback

Can you post a picture of yours.Alot of times on a rebuild this assembely (If taken apart)is intslalled incorrect causing it not to opperate at all or get stuck with a really dangerous partual throttlle position After a full throttle engagement

 

[JohnZ]

This is a '67 3810, but it's the same design as the 3367; in the photo you can see the plastic fast idle cam, in the "choke closed" position, with the tang on the linkage against the highest step on the cam (the progressively-smaller steps on the cam can be seen above the tang). The fast idle rpm is set by inserting a flat-bladed screwdriver in the slot in the tang and bending it in a clockwise direction, which opens the primary throttle shaft slightly at the same cam setting. Some of the "universal" Holleys (like the 1850 series) use a screw for this, down lower on the throttle lever.

 

[brumbach]

Unfortunately, I don't have the means to photo the finished product. I'm confident all is as parts are located where they're suppose to be other than achieving the 1500 rpm for fast idle. I'm only achieving 1000. It warms up, just takes longer than if idling at the spec requirement. Once warm though, it purrs like a kitten then roars like a lion when I put the pedal to the floor. Bill

Brumback

Can you post a picture of yours.Alot of times on a rebuild this assembely (If taken apart)is intslalled incorrect causing it not to opperate at all or get stuck with a really dangerous partual throttlle position After a full throttle engagement

 

[brumbach]

This is a '67 3810, but it's the same design as the 3367; in the photo you can see the plastic fast idle cam, in the "choke closed" position, with the tang on the linkage against the highest step on the cam (the progressively-smaller steps on the cam can be seen above the tang). The fast idle rpm is set by inserting a flat-bladed screwdriver in the slot in the tang and bending it in a clockwise direction, which opens the primary throttle shaft slightly at the same cam setting. Some of the "universal" Holleys (like the 1850 series) use a screw for this, down lower on the throttle lever.

Wow, what a simple, straightforward description of "how to" instruction. How do you know how much to bend the tang? I'm achieving 1000 rpm during warmup now. How do I know when I've bent it enough to get it to 1500 rpm? Others have told me the tang should rest on the second step of the cam. I understand that, but when bending the tang, how do I know that it'll rest on the second step when I start the car?

 

[knish71]

I'm very interested in getting a response to this question, as I am in the same perdicament. If I don't get a chance to check back, could you please drop me an email?

Thanks

Robert

 

[WayneC]

Seems like you guys are making this tougher than it needs to be... when you are doing this fast idle adjustment, you can place the tang and the fast idle cam to any position you want it, so start the car, open the throttle, rotate the cam until the tang is on the top step of the cam, and then use a screwdriver to bend the tang to achieve 1500rpm on the tach.

Now, which step the linkage will go to when you next start the car is a function of the engine temperature and the ambient air temperature, because those temperatures determine how much the remote choke spring expands or contracts, pulling on the linkage rod to position the butterfly and rotate the fast idle cam. It's possible to bend that linkage rod, but I don't think that is normally necessary. If the engine is already warmed up, even on a very cold day, you aren't going to see 1500rpm at idle after restarting it; if the engine is "cold" on a warm day, you may not see 1500rpm then either. If you adjusted the tang, and the engine doesn't achieve 1500rpm after starting a very cold engine on a very cold day, then MAYBE you need to bend the linkage rod.

All you're really trying to accomplish here is to keep the engine from stalling (or stumbling) at idle when the engine hasn't yet warmed up, so 1500rpm is the recommended setting, but it's not sacred.

 

[brumbach]

Well, I guess I just got lucky. I tried bending the darned thing before I received your input and by gollythe fast idle hit dead on 1500 rpm. The engine was cold and the outside temp was around 60. I'm not touching another thing. All works as it's suppose to, when it's suppose to. I'll save your advise for future application. Thanks so much. Bill

Seems like you guys are making this tougher than it needs to be... when you are doing this fast idle adjustment, you can place the tang and the fast idle cam to any position you want it, so start the car, open the throttle, rotate the cam until the tang is on the top step of the cam, and then use a screwdriver to bend the tang to achieve 1500rpm on the tach.

Now, which step the linkage will go to when you next start the car is a function of the engine temperature and the ambient air temperature, because those temperatures determine how much the remote choke spring expands or contracts, pulling on the linkage rod to position the butterfly and rotate the fast idle cam. It's possible to bend that linkage rod, but I don't think that is normally necessary. If the engine is already warmed up, even on a very cold day, you aren't going to see 1500rpm at idle after restarting it; if the engine is "cold" on a warm day, you may not see 1500rpm then either. If you adjusted the tang, and the engine doesn't achieve 1500rpm after starting a very cold engine on a very cold day, then MAYBE you need to bend the linkage rod.