'66 Roadster idle question

[Edward S.]

Just finished the rebuild of the Holly carb and got it on the car. Set idle RPM's according to manual at 450-500 RMP with standard trans. It seems a little too low to me. Idle sounds better at 600-650 rpm. The car is running excellent at either idle speed. Any thoughts would be appreciated as to the pro and cons of the two settings.

[Edward J.]

Re: '66 Roadster idle question

Ed, if the car idles great at 600/650 thats where I would set it. and when the time comes for having the car judged just set it to spec.s .I have a friend with a 67 sm / block and went through the same thing with his holley carb.

[Edward S.]

Re: '66 Roadster idle question

Thanks, Ed. This is my first go around with the rebuild of this carb so I am a little uncertain. I appreciate the information.

Ed S

[Timothy B.]

Re: '66 Roadster idle question

Edward,

From your post it sounds like you are working on a 300hp engine. This 500rpm has been discussed here before so some details are in the archives FWIW.

In the sixty's when these engines were made I believe the low rpm was achievable because of the old leaded gasoline. Today when tuning, you close off the throttle blades to set 500rpm and idle is so lean there is no fuel for power when the engine is put under load. No transfer slot exposed at idle and no air passing the blades to mix thus causing puddling of the fuel.

Idle timing of approx 21* (15 vacuum and 6 inital) will run good in your engine. There is good vacuum (low pressure) to gas the fuel in the intake manifold and the motor will feel good at the 650rpm setting because the throttle blade position and transfer slot exposure are set more correct for idle.

You can experiment with the secondary throttle blade stop screw to make sure blades are closed as this will allow the idle to drop and enable you to open the primary blades some for a better position at idle. Other than that, the air leak through the pcv can be reduced which will slow the idle and require the primary blades to be opened further which may help the engine feel stronger at that 500rpm but I would not do that.

Sorry for the long winded post..

[Edward S.]

Re: '66 Roadster idle question

Thanks, Tim. Exactly right, it is the 300 hp version. Your post was very helpful. Posts such as yours are the only way less experienced folks like me will learn and get better.