66 Skylark high idle

[Guest als 66]

My 66 skylark has the 300 cu in motor. Following a carb rebuild last year the motor has been running fine. Until last week. I was on the highway and the carb linkage seemed to be sticking a little. I pressed the gas to bypass the "sticking" and when I arrived at home I noticed that the car was idling too high. Now when I run the vehicle it doesn't idle down. As the engine heats up the higher the car idles. I'm clueless. Any ideas? Any help would be greatly appreciated.

[NTX5467]

Check the fast idle cam on the throttle side of the carburetor. With the choke open, IF it is openning all of the way as the engine warms up, the fast idle cam should decrease the idle speed appropriately.

As the engine warms up, the fast idle speed with increase, normally. But as the engine warms up, the choke thermostat should allow the choke to open and the fast idle cam to return to "not touching" the throttle speed adjusting screw.

With the engine off, move the throttle enough that the choke valve closes and the fast idle cam is activated. Then, manually open the choke valve to "full open" and see if the fast idle cam "drops out" as you manually open the throttle linkage a little, letting the throttle adjustment screw touch the carb body throttle stop rather than the fast idle cam.

Of course, make sure that the throttle linkage is letting the throttle return to base idle. Might even be that one of the return springs has failed?

IF the carburetor might have a "hot idle compensator" mechanism, that could be what's happening as it is supposed to allow a little additional air into the engine if the engine temp gets past a certain point. It's a "hidden" thermostatic flat spring with a rubber stopper at the end--if the rubber deteriorates, the compensator is not restricting the additional air from entering the carb AND it's not controlled by the idle speed screw. This is an additional "air circuit" that some carbs used and others didn't.

Just some thougths. Keep us posted with what you find.

NTX5467

[JohnD1956]

I agree with NTX, sounds like one or more of the throttle rods were bent when you tried to push past the sticking throttle. If you have a manual for the car you really need to study how to adjust those rods. There's so many carbs out there, and so many applications, it's impossible to tell you how to fix this problem with any degree of confidence. If you are unable to reference any such material I suggest you contact CARBKING on these forums and see what he can recommend.

[Guest als 66]

Thanks guys. My thought was that something was bent also, but I can't find anything. I have an un-rebuilt carb that I compared the linkage with and nothing looks bent. I'll try to reach the CARBKING and see if he can help.

Thanks, AL

[buick5563]

Also, did you replace the return spring for the linkage? When I was working on a friends 60 Electra, I discovered that someone had installed a double spring and the outer was physically sticking on one of the carb bolts.