manual choke issue - Chevelle Tech
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post #1 of 12 (permalink) Old Mar 29th, 15, 10:12 AM Thread Starter
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Tyler
 
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manual choke issue

I finally got around to putting in my manual choke pull cable on my Holley 750 DP. Before installing the cable however I wanted to make sure my choke worked correctly. I closed the choke off by hand and attempted to start it up, leaving a pencil width gap with the choke plate closed (as recommended by holley). Engine started up but stumbled around and I still had to feather the accelerator to keep it running. Tried a few different choke positions with same result. Opened the choke back to full open and started up again and it runs nice and smooth. Still must feather the pedal for a minute or so till it builds some heat but then idles nicely. Any ideas on why its not liking the choke? Only reason Id like to hook it up is so I don't have to feather the throttle on cold starts.
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post #2 of 12 (permalink) Old Mar 29th, 15, 10:23 AM
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Re: manual choke issue

With a cold engine, I always pull the choke all the way out then push it back in a little when the motor starts.

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post #3 of 12 (permalink) Old Mar 29th, 15, 11:10 AM Thread Starter
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Re: manual choke issue

it doesn't seem to want to cold idle even when fully closed though and still stumbles.
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post #4 of 12 (permalink) Old Mar 29th, 15, 11:26 AM
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Re: manual choke issue

If your carb does not have a throttle idle step up position when the choke is engaged then your going to have to manually raise the idle with your foot. The choke plate should open a minimum amount on a cold engine and as it warms you can open it more to fully open.

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post #5 of 12 (permalink) Old Mar 29th, 15, 11:50 AM Thread Starter
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Re: manual choke issue

yea I believe your right about the throttle step up. makes sense
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post #6 of 12 (permalink) Old Mar 29th, 15, 11:59 AM
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Re: manual choke issue

If you adjust the fast idle cam up a little like Eric said, it should run OK.
You just might have to remember to hold the accelerator down a little while pulling out the choke to allow the fast idle cam to rotate.

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post #7 of 12 (permalink) Old Mar 29th, 15, 12:57 PM
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Rob
 
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Re: manual choke issue

I hope you ran that choke cable straight back through the firewall so that the knob is easy to pull.

Yes you need to adjust the fast idle screw on the choke. Hard to get to those screws on the 750, it's not a straight shot to the screw which makes it a pain to adjust.

65 Chevelle 2Dr. Post,Global West stage 3, Small Block, Small Journal 337cid. Howards roller cam .570/.570" lift 227/233 duration @ .050 LS112, Speed Pro forged pistons 10 to 1, Trick Flow 195,23 degree heads, Holly 750 Ultra, Edelbrock Performer RPM air gap.

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post #8 of 12 (permalink) Old Mar 29th, 15, 1:45 PM Thread Starter
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Re: manual choke issue

I haven't actually installed the cable yet. wanted to figure out my choke situation first. Im a bit of a carb adjustment dummy. I can adjust the main idle screw on the throttle side and thats about out. carb always performed great so ive never really had to mess with it.

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post #9 of 12 (permalink) Old Mar 29th, 15, 2:20 PM
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Re: manual choke issue

Quote:
Originally Posted by Tcbullion View Post
I haven't actually installed the cable yet. wanted to figure out my choke situation first. Im a bit of a carb adjustment dummy. I can adjust the main idle screw on the throttle side and thats about out. carb always performed great so ive never really had to mess with it.
Yes the choke is just to make warming up a bit easier and hopefully not have to keep your foot on the gas the entire time. The fast idle screw is just under the choke parts on the passenger side, it's pain to get to but it's doable. You need to turn that up until it can hopefully idle when cold, as you pull the choke it also rotates the cam and sets the fast idle at the same time.

You really need to run the choke cable straight back from where it mounts on the carb through the firewall because if you try bending it down and around everything you will end up with a very stiff and extremely difficult to pull choke that probably won't return to the straight up position like you want. It pretty much sucks that way and you won't like it.

On my 65' the cable goes straight back from the carb through the firewall 5" down from the top, I just drilled a 1/4" hole and used a small rubber grommet to pass the cable housing through. You need to size the hole for the grommet you are using. I found a really small one so only needed a 1/4" hole.

It comes out just to the right of the defrost vent and over the heater nice and straight, then it bends over slightly to the drivers side and mounts under the dash. Super easy to pull this way.

You will also need to cut the housing and the cable to the proper length. The more bends you add to that cable the worse they work.

65 Chevelle 2Dr. Post,Global West stage 3, Small Block, Small Journal 337cid. Howards roller cam .570/.570" lift 227/233 duration @ .050 LS112, Speed Pro forged pistons 10 to 1, Trick Flow 195,23 degree heads, Holly 750 Ultra, Edelbrock Performer RPM air gap.

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post #10 of 12 (permalink) Old Mar 29th, 15, 5:25 PM Thread Starter
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Re: manual choke issue

thanks for all the info here guys. Ill work with it more tonight.

Tyler B
70 chevelle 454,TH400,3.31 12 bolt posi
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post #11 of 12 (permalink) Old Mar 30th, 15, 9:32 AM
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Re: manual choke issue

As the guys explained, it is probably about technique. One of the reasons that manual chokes were discontinued was that people could not learn how to use them.

As Dean stated, you close it all the way, start the engine, and as soon as the engine starts, you open it a tiny bit.
oldcutlass gave you the next step. A manual choke needs a manual throttle, or you need to use your foot on the accelerator instead. A cold engine needs more fuel to run. You supply that with either a throttle cable or your foot.
As the engine warms up, the increased throttle setting is no longer needed and you can open the choke up slowly as the engine no longer needs it.

Manual choke delivered by the manufacturers was an "engineered" design. The earlier models had separate choke and throttle cables. The later versions had the throttle linkage incorporated into the choke cable so it was all done with a single cable. If you want a manual choke try to copy the factory setups, and it will work great.
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post #12 of 12 (permalink) Old Mar 30th, 15, 12:40 PM
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Re: manual choke issue

I just put a felt pen mark on the choke cable where I can easily see it at the correct opening.

You can also install a collar or use the cable housing to set up a stop point where the cable connects to the carb.

65 Chevelle 2Dr. Post,Global West stage 3, Small Block, Small Journal 337cid. Howards roller cam .570/.570" lift 227/233 duration @ .050 LS112, Speed Pro forged pistons 10 to 1, Trick Flow 195,23 degree heads, Holly 750 Ultra, Edelbrock Performer RPM air gap.

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