Idle Adjustments for Winter & Summer

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Old Mar 27, 2020 | 05:37 PM
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chenner's Avatar
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Idle Adjustments for Winter & Summer

Hi guys,

I moved at the end of last fall but before I did I had my '69 442 with a 455 "tuned up" by my local shop. At the time he told me that he was raising the idle for the colder temps and that he'd adjust it back down when I bring it by back in the spring. However, he's now an hour and a half away from me so it's more convenience for me to get somebody in my local town to do this for me.

I dropped it off for an oil change with a local mechanic (who came recommended for his work on old cars) and asked him to adjust the idle as well. When I picked it up he told me that he had lowered it to what the sticker on the engine bay says which is 650 rpms. Well since he did that it's been having occasional problems starting when warm (it dies right away sometimes) and I'm even getting some surging. I'll have to ask him what the idle was before he adjusted it so that I can bump it back to what it was.

My question is that did my original mechanic mean that I should adjust the fast idle or the warm idle? I'm thinking the fast idle as it started at 1,600 rpm this morning on a cold start but I just want to be sure.
Do I just want to adjust the fast idle lower for the warmer temps and leave the warm idle alone?

Any advice is appreciated.

Bill
Old Mar 27, 2020 | 07:41 PM
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There are 2 different adjustment screws, 1 is the choke high idle adjustment and the other is the curb idle adjustment. There should not be a winter/summer difference in your adjustments.
Old Mar 27, 2020 | 07:58 PM
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Due to temp I don't see a reason to adjust either the base idle speed (driver's side of carb) or the high idle speed (pass side) assuming it is a Qjet.
Your first mechanic may have adjusted the choke thermostat for winter/summer if yours is adjustable.

Can you post a picture of the pass side of your carb with the air cleaner out of the way so we can see the choke thermostat?
​​​​​

Last edited by Sugar Bear; Mar 27, 2020 at 08:01 PM.
Old Mar 29, 2020 | 07:36 AM
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Originally Posted by Sugar Bear
Can you post a picture of the pass side of your carb with the air cleaner out of the way so we can see the choke thermostat?
​​​​​
I've got OAI snorkles attached to my air cleaner but I've lifted it here for the third pic. Does this show you what you wanted to see?




Old Mar 29, 2020 | 09:49 AM
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That is the drivers side in your pictures and your carb is an Edelbrock.
Old Mar 29, 2020 | 10:52 AM
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My bad, I'm an idiot lol. Here are pics of my carb from the passenger side:


Old Mar 29, 2020 | 11:07 AM
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Adjust the screw in this picture clockwise a 1/4 turn until you reach 750 rpm on your tach and see if that works for you.
Old Mar 29, 2020 | 02:00 PM
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Carb as stated is an Edelbrock vs an OE Qjet. It does have what appears to be an adjustable choke thermostat, the black round disc with two wires in the last picture. Ask the mechanic that last worked on it if that was adjusted, if not ask what was adjusted.

Good luck!!
Old Mar 29, 2020 | 02:16 PM
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Originally Posted by oldcutlass
Adjust the screw in this picture clockwise a 1/4 turn until you reach 750 rpm on your tach and see if that works for you.
I'll give that a go - thanks!

BTW, there's a screw behind it that you can't really see. The mechanic told me that it's for my fast idle. Should I dial it back from the 1,600 rpms I'm getting now with the choke set?
Old Mar 29, 2020 | 02:16 PM
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Originally Posted by Sugar Bear
Carb as stated is an Edelbrock vs an OE Qjet. It does have what appears to be an adjustable choke thermostat, the black round disc with two wires in the last picture. Ask the mechanic that last worked on it if that was adjusted, if not ask what was adjusted.

Good luck!!
I'll give him a call tomorrow and ask.

Thank you!
Old Mar 29, 2020 | 03:18 PM
  #11  
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Originally Posted by chenner
I'll give that a go - thanks!

BTW, there's a screw behind it that you can't really see. The mechanic told me that it's for my fast idle. Should I dial it back from the 1,600 rpms I'm getting now with the choke set?
I like them set at 1400, but that's not much of a difference.
Old Mar 30, 2020 | 06:20 AM
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Originally Posted by oldcutlass
I like them set at 1400, but that's not much of a difference.
Perfect, thanks for your help.
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