Re: 1950 327 with Ultramatic - Idle Speed

Posted by JWL On 2023/2/5 14:29:13

Setting the idle speed is a two part process. There is the idle speed adjustment and the idle mixture adjustments.

I set the idle with the engine in neutral and fully warmed up with the choke in full open position.

First, I set the idle speed to the desired rpm with the adjustment screw.

Then I adjust the idle mixture with the two jet screws at the base of the carburetor. Usually start out with the mixture jets screwed out one and one-half turns. Then screw one of them in until the engine starts to slow down and screw it out about one-half turn. Repeat for the other idle jet.

You may need to adjust the speed adjustment again.

Repeat procedure until you achieve the desired rpm.

I have the air cleaner installed when doing this.

It is also a good idea to disconnect the distributor vacuum chamber tube from the distributor and plug it. This usually not necessary, but insures the vacuum chamber is not being activated. More of a belt and suspenders thing.

Some use a vacuum gauge to optimize the idle mixture adjustments. This is a good idea.

Hope this helps.