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

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.

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.

Jon, since I’m running a manual transmission is depressing the HIC still
something one should do?
Thanks,
Don

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.

What is the process for plugging the HIC?

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.

Let me rephrase the question.
What do you recommend to plug the hole with?

The commercial rebuilders used the aluminum passage drive plugs used in Carter AFB carburetors.

Jon.

Thanks for the reply Carbking.
Where can I buy one of these aluminum passage drive plugs? Will this press in without any modification?

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.

You guys are spot on. I was able to get some plugs from Amazon. They fit perfectly.
You guys are awesome.
Thanks so much!

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.

Holley 26-111-10 Metering Block Plug
These are the plugs I bought.
They are just over 1/4” and press in nicely.

Glad the Holley Plugs work for you dlloyd and thanks for posting the metering block plug number.

Tom V.

Thanks