Holley choke adjustment? - Team Camaro Tech
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post #1 of 4 (permalink) Old Dec 13th, 05, 05:11 PM Thread Starter
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Holley choke adjustment?

I am having a problem with my 350 not wanting to idle if I kick off the fast idle before the car is fully warmed up. I'm also having a problem with the fast idle not disengaging when the choke is fully opened. I am running a new Holley 750 vacum secondary. The only adjustments I've made to the out-of-the box settings are: 1) adjusted the front float level slightly to the proper setting, the rear was okay 2) adjusted the idle mixture screws 1/4 turn in to get the most vacum at idle, 20".

When I get ready to start the car I pump the gas pedal once to set the choke, and the choke closes all the way. Turn the key and it fires up and then sounds like it wants to die so I turn it off. I pump the gas pedal again and it fires up again and sounds like it wants to die so I turn it off. I pump the gas pedal again and it fires up and the fast idle takes over and it idles at 1400 RPM. If I kick off the fast idle before the engine is fully warmed up I have to keep patting the throttle to keep it running. Once warmed up it idles fine at 850 RPM and runs great. If I don't kick off the fast idle it won't come off by itself when the choke if fully opened. I've let it run 10 minutes to see if it would kick off by itself and it doesn't.

Any ideas would be greatly appreciated.
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post #2 of 4 (permalink) Old Dec 13th, 05, 08:19 PM
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Re: Holley choke adjustment?

A conventional fast idle will not fall off by itself, only when you "kick it" The choke link holds it up, but the link is slotted so it doesn't get pulled back down.
In an ideal world, the fast idle wouldn't fall all the way the first time you kick it. There are 3 or 4 steps on the cam, and it should fall to a lower step, and idle slower, every little bit the choke blade opens.
You can play with the choke adjustment (the round housing) the length of the fast idle link (bend it) or the fast idle throttle stop (screw on some carbs, link you bend on others) to dail it in. It's not easy to get perfect.

Edit: next time pump it 4 times before you crank it, might want a lil more shot of fuel to get going stone cold.

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post #3 of 4 (permalink) Old Dec 14th, 05, 04:42 AM
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Re: Holley choke adjustment?

Suggestions JimM gave are good. From my experience, it has taken me a few days to set the choke for excellent running.

You have an electric choke which should be hooked up to a full 12 volts, and not pigtailed from the coil wire and a ground.

I had to set the choke for two settings depending upon season, ie, summer - leaner or winter - richer.

You fast idle rpm of 1400 is good. Just be sure, in the morning when coldest, once you've open the throttle to WOT, the choke plate closes completely, it should 'snap' shut and the fast idle cam kicks in. If not, fix it, maybe a squirt of lube.

On the black cap, choke heater, loosen the three screws and rotate the cap towards 'RICHEN' a notch or two from the center. Clamp down the cap and test. Take note, if the engine stumbles less, then you are going in the correct direction. If the engine runs worse, reverse the direction towards 'LEANER'.

Make an adjustment and test the next day when the engine is cold. Adjust the choke cap a notch or two at a time in the direction of better running.

The ideal set-up is coming out, hit the throttle at least twice, start the engine, it fast idles, warms up, and fast idle kicks out. This all can happen with the vehicle setting for three minutes or start the engine, let run for 20 seconds, then drive, no bogging, no backfire, just smooth running.

It takes time, patience, and a mental notebook of cause & effect when an adjustment is made.

If the vehicle ran good during warm weather cold engine, mark the position before doing any adjustment to mark for summer operation.

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post #4 of 4 (permalink) Old Dec 15th, 05, 08:58 AM
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Re: Holley choke adjustment?

As was said above, it takes some trial and error to get it just right. Here's what the Holley site http://www.holley.com/data/Products/...199R9934-3.pdf
says about choke adjustment:

IMPORTANT: Your Holley carburetor has been factory wet-flowed and calibrated. The “out of the box” settings should be very close for all adjustments. The following tuning section is included ONLY to aid you in fine tuning adjustments.

Electric Choke

1. You can control the choke operation by rotating the choke cap. If the choke comes off too soon, rotate the cap counterclockwise one notch at a time, until the choke operation is satisfactory. Reverse the procedure by loosening the screws, if the choke comes off too late. The choke setting from the factory is on “index” or at center position. After making the final adjustments, start the engine and make sure the choke plate opens completely.

A. A choke that comes off too soon could exhibit one or more of the following symptoms: stalling, surging, backfiring, stumbles, or poor vehicle driveability when the vehicle is cold.

B. A choke that comes off too late could exhibit one or more of the following symptoms: black smoke from the tail pipe, poor driveability when cold, poor gas mileage, misses, or rough idle.

Manual and Electric Chokes

2. If the fast idle RPM is too low or too high for your preferences, SHUT DOWN THE ENGINE! Advance the throttle to wideopen, exposing the fast idle set screw below the choke housing (See Figure 8).

3. Using a 1/4” open end wrench, turn the screw clockwise to increase the RPM or counterclockwise to decrease the RPM. The factory setting should give you a 1500-1600 RPM fast idle speed.
NOTE: All vacuum ports must be plugged at this time."

Also, make sure the choke pull-off is working. This is a little vacuum can (in the choke housing) that cracks open the choke slightly, right after the engine starts. If it's not working, then the choke stays shut and the engine runs too rich. With a cold start, the choke should be shut tightly, but should crack open as soon as the engine fires off, without you having to touch the gas pedal.

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Last edited by Chevy-SS; Dec 15th, 05 at 09:15 AM.
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