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Old 01-29-2020, 02:45 PM
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Default Hot Idle Compensator When Adjusting Idle

Hi,
I have a question that until recently I never really paid much attention to.

In the Pontiac Service Manual it says to depress the Hot Idle Compensator while adjusting the idle.

Now, Ive never done this and would like to know if it is something that should be done.

I know Tom Vaught's answer already "engineers do things for a reason" ha ha

Thanks,
Don

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1966 GTO

1966 421-9.3-1 comp-Race Tec 23cc Pistons
1966 Tri-Power
1967 670 Heads
Pontiac "Highlift" TriPower Cam by SpeedPro
DUR 214 Int 224 Exh @.050 - 107 ICL
LIFT .445" Int .465" Exh
Tri-Y-Headers by Tribal Tubes w/ Goerlich Mufflers
1966 Muncie Wide Ratio 4-Speed
1968-72 Chevy 12 Bolt Rear End w/ 3.73 rear gears
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Old 01-29-2020, 02:59 PM
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If the HIC valve is open when the Curb Idle is set, THEN when the HIC Valve is closed and the Fast Idle Cam is off, the Curb Idle of the engine may be too low and the engine may stall.

So you close the HIC Valve, (manually) and set the idle with the engine warmed up, You will know for sure the curb idle is correct (if the HIC Valve is operating properly) that it will ONLY ADD extra air to the carb/Intake/Engine under a High Thermal Condition and cause the cooling system to be more efficient due to a higher engine rpm.

Barry Grant claimed to have invented the Idle Air By-pass System "Idle EZE" for carbs but Pontiac had a By-pass idle circuit built into the Rochester 2 BBL Carbs, HIC VALVE, (years before the Barry Grant's claim) on millions of Pontiac engines.

Carter Carbs also had a Idle Air By-Pass Circuit on AFB carbs. It was a manual setting system.
HIC valve is thermally controlled.

Hope that makes sense.

Tom V.

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Old 01-29-2020, 06:09 PM
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Tom - Carter also had the idle air bleed system on a few of the WCFB carbs.

Don - in the FWIW category, if you end up with a carb that has been "rebuilt" by a commercial carburetor rebuilder, you may not see a hot idle compensator; as most of them were removed, and the channel plugged. The HIC was pretty much only used on cars with automatic transmissions.

Jon.

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Old 01-29-2020, 06:12 PM
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Jon, since Im running a manual transmission is depressing the HIC still
something one should do?
Thanks,
Don

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1966 GTO

1966 421-9.3-1 comp-Race Tec 23cc Pistons
1966 Tri-Power
1967 670 Heads
Pontiac "Highlift" TriPower Cam by SpeedPro
DUR 214 Int 224 Exh @.050 - 107 ICL
LIFT .445" Int .465" Exh
Tri-Y-Headers by Tribal Tubes w/ Goerlich Mufflers
1966 Muncie Wide Ratio 4-Speed
1968-72 Chevy 12 Bolt Rear End w/ 3.73 rear gears
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Old 01-29-2020, 11:30 PM
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Don - Pontiac couldn't seem to decide if they wanted HIC on manual tripowers, or not. 1965 did not, 1966 did.

With a modified engine, as you have, I would probably plug it.

If you are going to use it, then adjust as suggested by the factory.

Jon.

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Old 02-10-2020, 10:28 PM
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What is the process for plugging the HIC?

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Old 02-11-2020, 12:13 AM
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On a '65 or earlier setup, remove the rear HIC cover and HIC mechanism. Plug the hole.

On a '66 carb, remove the HIC mechanism and plug the hole going to the carb base.

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Old 02-11-2020, 10:26 PM
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Let me rephrase the question.
What do you recommend to plug the hole with?

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Old 02-12-2020, 09:43 AM
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The commercial rebuilders used the aluminum passage drive plugs used in Carter AFB carburetors.

Jon.

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Old 02-12-2020, 06:19 PM
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Thanks for the reply Carbking.
Where can I buy one of these aluminum passage drive plugs? Will this press in without any modification?

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Old 02-12-2020, 09:25 PM
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If you can get the cup plug from a Holley metering block, it should be the same size as the HIC drilled passage.

Tom V.

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Old 02-18-2020, 08:52 AM
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You guys are spot on. I was able to get some plugs from Amazon. They fit perfectly.
You guys are awesome.
Thanks so much!

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Old 02-18-2020, 11:01 AM
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dlloyd what did you type in on Amazon to get those plugs to come up? I just tried "carburetor plugs", "aluminum plugs", and several others and got nothing or things other than plugs.

I've always used JB Weld to plug the hic circuits.

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Old 02-18-2020, 04:50 PM
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Holley 26-111-10 Metering Block Plug
These are the plugs I bought.
They are just over 1/4 and press in nicely.

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Old 02-18-2020, 09:24 PM
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Glad the Holley Plugs work for you dlloyd and thanks for posting the metering block plug number.

Tom V.

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Old 02-19-2020, 01:52 PM
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Quote:
Originally Posted by dlloyd View Post
Holley 26-111-10 Metering Block Plug
These are the plugs I bought.
They are just over 1/4 and press in nicely.
Thanks

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