To separate the idle cam from the choke

At some point I would like to separate the idle cam on my carb from the choke and have an adjustable idle setting that doesn't involve the choke plate.

The reason being that in weather that is on the warmer side I can start my car and adjust the idle for the engine to warm up without the choke being involved.
Or I can set the idle wherever I want it.

The way it works right now is I start the engine and it may not be cold enough to set the choke enough to set the idle higher.
I don't want to set it to choke more just to have a higher warm up idle.
I also usually let the engine warm up close to running temp before I drive it and it would be nice if it could idle at say 1,200 RPM instead of 500 until it warms up all the way.

If I smooth the idle cam steps off so the cam is smooth but still ramped and polish the screw tip a little convexed and lube it with a little grease I should be able to alter the idle speed without ever touching the throttle.

I could make it real simple and just use a choke cable kit, but I would much rather have a twist dial instead.
I could build that using a cable kit, a threaded rod, a few small washers , a few nylock nuts, and a bracket to contain the twist to push pull conversion mechanism.

Don't think I have ever seen a device that converts push pull to a dial.
I even thought about using a stepper motor and controller, but even though that would probably be cleaner I wouldn't have a random cable under the hood it would cost a lot more.
I could use something like a twist and lock throttle cable but no one seems to make one compact enough, as they are all big bulky industrial looking things.

About a 1 inch round knurled edge twist knob that moves a cable in and out about 1/8 inch per one full knob rotation would be perfect.

Any idea I might be missing?

Wouldn't it be simpler to just run a manual choke? That way you can adjust the choke and idle speed where you need it.

Murray said:

Wouldn't it be simpler to just run a manual choke? That way you can adjust the choke and idle speed where you need it.

Click to expand...

If also installed with a manual throttle.

TrailBeast said:

The way it works right now is I start the engine and it may not be cold enough to set the choke enough to set the idle higher.
I don't want to set it to choke more just to have a higher warm up idle.

Click to expand...

Totally sympathetic with that issue.
Here's what I've learned about how an automatic choke is supposed to work. You'll have to investigate whether either of the carbs you've got has all the features.

Initial Choke position: This is where the plate sits when the engine off. Its the maximum restriction to the carb entry.
Qualified Choke position: Plate position immediately upon starting.
* It's opened by manifold vacuum.
* The amount it opens is usually adjusted by increasing or decreasing the spring force on a vacuum diaphram.
* Usually the linkage is such that the qualified position is based on the initial position, not independent.
* It does not effect the throttle fast idle position.

Fast idle cam has two or three steps. In warmer weather the cam's linkage to the choke should rotate it off the upper step(s) pretty quick.
* There may be a way to have the choke 80% open and still have the cam rotated so the throttle is on the second step.

Some carbs have internal vacuum source connection to the choke. They may or may not have a means of adjustment if its internally connected. Some carbs don't have any vacuum source. I think the only solution for them is set the choke for the running position and use pump shot from working the throttle to get it rich enough to fire off.

My own preference is for the choke bimetal to be getting heat from the intake since the intake's temperature is what matters. But that's too complicated for aftermarket carbs so that's not a realistic choice in most cases.

Murray said:

Wouldn't it be simpler to just run a manual choke? That way you can adjust the choke and idle speed where you need it.

Click to expand...

Not if I want control over the idle speed only.
What if the car is all warmed up and yet I want the idle to be a little higher or even lower temporarily?
Much rather have a dial to increase or decrease just the idle without involving the choke.

Mattax said:

If also installed with a manual throttle.



Totally sympathetic with that issue.
Here's what I've learned about how an automatic choke is supposed to work. You'll have to investigate whether either of the carbs you've got has all the features.

Initial Choke position: This is where the plate sits when the engine off. Its the maximum restriction to the carb entry.
Qualified Choke position: Plate position immediately upon starting.
* It's opened by manifold vacuum.
* The amount it opens is usually adjusted by increasing or decreasing the spring force on a vacuum diaphram.
* Usually the linkage is such that the qualified position is based on the initial position, not independent.
* It does not effect the throttle fast idle position.

Fast idle cam has two or three steps. In warmer weather the cam's linkage to the choke should rotate it off the upper step(s) pretty quick.
* There may be a way to have the choke 80% open and still have the cam rotated so the throttle is on the second step.

Some carbs have internal vacuum source connection to the choke. They may or may not have a means of adjustment if its internally connected. Some carbs don't have any vacuum source. I think the only solution for them is set the choke for the running position and use pump shot from working the throttle to get it rich enough to fire off.

My own preference is for the choke bimetal to be getting heat from the intake since the intake's temperature is what matters. But that's too complicated for aftermarket carbs so that's not a realistic choice in most cases.

Click to expand...

One carb I may use (The Holley Avenger) has the bimetal electric heated style and also a vacuum activated choke pulloff.
If I were to do it with this carb it would be really easy since the idle cam is not physically connected to the choke butterfly.
The cam is lifted by an L in the choke plate linkage rod that goes under the cam and lifts it.
If I did it with this carb and my dial inside the car was backed off to it's lowest setting the entire carb choke and high idle linkage would work exactly as designed by the OEM.

On the 750 Edelbrock electric bi metal the choke and high idle cam are physically connected with a rod, so I would have to separate them by removing that rod or the choke would close some when the idle speed was increased.
And it would always be separate from the choke and not work as designed if I didn't use the manual high idle knob.
This one I would have to use the manual high idle every time I start the car instead of it working normally if I didn't use the manual device.

That's one point in favor of the Holley, but I'm not going to use it just because of this.
I'll decide which carb I like best and then make the mods needed.

Timing.
Plum your vacuum advance to one of those thermo-vacuum switches that switch between ported and manifold vacuums, based off the water temperature. You can get them in a variety of different switch points. In this way the idle speed remains relatively stable as the thermo is reducing signal to the can as the coolant warms up, which reduces the timing assist. It took me a couple of tries to get the right device, but I thought it was pretty slick. And it was automatic
IIRC your Vcan is over 20* which might be a lil much, depending on your initial, but maybe your cold engine will not suck it all in. Besides, both of those are adjustable.

What I eventually did was install a dash-mounted, dial-back, timing control with a range of 15 degrees. Different plan of attack, but same results. The dial is usually set to option; 5* retard and 10* advance. So on a cold engine I can dial in 10 over the 14 in the Initial. That's lots enough for my combo.

How about a small (they make them LOL) gearhead 12V motor connected to a replacement curb idle screw. So long as the motor electrics is isolated from ground (such as PM with two commutator wires) all you need is a momentary, center off, DPDT switch to reverse/ forward the motor, and screw the curb idle in/ out

Such as

DC Motors | MPJA.COM

12VDC, 5 RPM Gearhead Motor ZGA37RG244i | MPJA.COM

How about a curb idle kicker like what came on my manual trans 1970 340.

AJ/FormS said:

How about a curb idle kicker like what came on my manual trans 1970 340.

Click to expand...

Along that line, how about an AC idle compensator kicker rigged up so you control it?

Google vernier control cables. It is almost exactly what you describe. Can rotate knob to adjust throttle. The ones i sold in the past had approx 1” diameter knob.used with a bead chain, it wont affect normal operation.

my 68 chevy had a manual choke, pull it out and start it, and then i could keep idle up with choke off. If i wanted fast idle,i could feel the steps in the pedal. Was the only manual choke vehicle that would work like that,most didnt work as well.

all the aftermarket choke kits are junk, especially the cable control.

put 4.30s in the back and all your problems will disappear,lol.
No more hesitations, no bogs, no flat spots, no waiting for the intake to warm up, no more compensating for Sunday Drivers or lil old ladies. And the gasgauge finally works normal, lol.
Caution; leave the wife at home, or she'll ***** and moan about her sore neck and tired abs. Kids too; only one of my three liked getting torqued around. The other two did not think figure 8s,donuts,or drifting was near as much fun as I did. But then, their idea of fun was stomping in puddles and getting Daddy's pants all wet; sure, that was hilarious.... to them.
Get in the back kids,buckle up, ..........
Davie; yur ridding shotgun again, where's yur booster seat?
Com'on girls hustle,
yeah-yeah, I'll drive nice......
hang on to eachother.........

Somebody has to ask so it will be me. Why? Why do you need fast idle when the engine is warm? I am with Kowalski. A a/c solenoid hooked up to a toggle switch would do the trick. Not adjustable though. Hook a cable up to the fast idle cam.

Trailbeast,
Police cars used to have an idle step up control, had a couple early 80s Diplomats. Decades ago, but think it was a T- handle, pull it back, twist to lock.

Your post suggests EFI and electronic advance in your future.... With idle air, control, and ignition timing with temperature adj, your idle and overall running can be perfect all the time.

toolmanmike said:

Somebody has to ask so it will be me. Why? Why do you need fast idle when the engine is warm? I am with Kowalski. A a/c solenoid hooked up to a toggle switch would do the trick. Not adjustable though. Hook a cable up to the fast idle cam.

Click to expand...

Right. Either its not quite warmed and a bit of choke won't hurt and will keep it on the high idle step (like TJ's Chevy), or it is warmed up.
Earlier manual chokes often had a manual throttle too as a seperate control.

67Dart273 said:

How about a small (they make them LOL) gearhead 12V motor connected to a replacement curb idle screw. So long as the motor electrics is isolated from ground (such as PM with two commutator wires) all you need is a momentary, center off, DPDT switch to reverse/ forward the motor, and screw the curb idle in/ out

Such as

DC Motors | MPJA.COM

12VDC, 5 RPM Gearhead Motor ZGA37RG244i | MPJA.COM

Click to expand...

Believe me, I have considered this route but did want to go to all the expense details to add another electric device and over complicate this.

AJ/FormS said:

How about a curb idle kicker like what came on my manual trans 1970 340.

Click to expand...

That was my first thought, but one position only isn't worth it to me to do.

kowalski440 said:

Along that line, how about an AC idle compensator kicker rigged up so you control it?

Click to expand...

Same answer as I gave AJ.

Tooljunkie said:

Google vernier control cables. It is almost exactly what you describe. Can rotate knob to adjust throttle. The ones i sold in the past had approx 1” diameter knob.used with a bead chain, it wont affect normal operation.

my 68 chevy had a manual choke, pull it out and start it, and then i could keep idle up with choke off. If i wanted fast idle,i could feel the steps in the pedal. Was the only manual choke vehicle that would work like that,most didnt work as well.

all the aftermarket choke kits are junk, especially the cable control.

Click to expand...

The manual choke route is actually closest to what I want to do, but I'm kind of a "One off" type.
Just a simple twist knob to raise or lower the idle without involving the choke or I'm not going to bother.

toolmanmike said:

Somebody has to ask so it will be me. Why? Why do you need fast idle when the engine is warm? I am with Kowalski. A a/c solenoid hooked up to a toggle switch would do the trick. Not adjustable though. Hook a cable up to the fast idle cam.

Click to expand...

I don't "need" it, but it might be something to do while it rains for days like the weather report says.
I'd like my idle a little higher some times but not others.
Pretty sure I have made a decision, but I'm going to check the links Tooljunkie posted just in case.
Probably will end up using a cable like a choke kit uses, but I want the adjustment to be finer increments than just the push/pull like a a choke.
AND in doing this I want to get rid of the steps in the idle cam and make it a smooth transition so I don't have to touch the throttle at all to adjust.

I know, everyone should have such big problems.

The vernier cable was commonly used in heavy truck applications,thread out to increase idle,push on button and it would release.
Hino i drove for delivering water had. It would take about 15 minutes and it would finally warm up. Set it at 600 rpms,and go inside and drink coffee. Could hear it start to rev up,had to run to idle it down,as it would go wide open if you left it too long.