'64 High Idle Problem

[tharrill]

Does anybody know how to solve a high idle problem on a ’64 Avanti R2?  The problem is best described as the engine idles (above 1000 rpm) unless I rapidly depress and release the throttle pedal (kicking down the idle).  It is not due to the engine being cold and the throttle being on the fast idle cam.  It occurs whether the engine is hot or cold.  It is not due to the dashpot either.

It is also not the carburetor as I have switched to a different carb and it exhibits the same behavior.   The only thing (at least in my mind) that could be causing it is either the throttle linkage is sticking or the throttle return springs are too weak.  I tried moving the linkage at the carb and it appears to move freely and is not binding and the return springs I purchased from a reliable vendor so I am assuming they are the correct ones.

I am getting tired of kicking down the throttle at stop lights.

Any thoughts?  My thanks in advance and any help or advice is appreciated.

Tom Harrill

[mfg]

Hi Tom, the good news here is that this problem isn't unique to your '64 Avanti....It has shown up on many Studes equipped with Carter AFB carbs....even the newer Edelbrock version will sometimes behave this way.

Looks like you've checked all of the 'usual suspects', however, I would definitely increase the throttle return spring pressure some, and more importantly 'loosen up'  the throttle linkage a little more.

Of course, the Avanti manual gives specs on throttle linkage adjustment, but basically you want the throttle linkage, when completely clear of the fast idle cam, to be pushing AGAINST the ball socket of the carb throttle lever. (i.e. to be pushing the lever forward when linkage is at rest.)

Also, try to lubricate all moving linkage parts on the carb and the throttle linkage itself with PB Blaster or WD 40......Ed

PS.....You can also try (with the engine turned off and choke plate completely open) to wind out the idle speed screw well beyond where the engine could actually run...then open and close the throttle by hand rapidly pushing firmly against its fully closed position....Doing this will alleviate any built up varnish on the throttle blades or carburetor barrel walls that sometimes keeps the throttle open slightly too far.

Edited September 4, 2019 by mfg
Added PS