Rumpity Rump

Its only the primary butterflies that do this. They appear to be sticking on the frontside of the venturi and will not allow the idle to return to its proper setting unless you take your finger and move the return mechanism manually. Ive tried a stronger return spring to no avail. Any thoughts ? Thanks, RR

lars

Rump -
If they're really binding against the holes in the throttle plate, you can simply re-align them. To do this, you will need to remove the carb and remove the throttle plate from the bottom of the carb. This is relatively easy to do after you remove the accel pump rod and make note of the installed orientation of the secondary lockout lever.

With the entire throttle plate assembly removed, you can access the individual throttle plate attach screws. These screws are staked in place in the throttle shaft, so you cannot completely remove them without breaking them off (unless you grind/file off the staked part on the back side). However, you can loosen them about 1/4 - 1/2 turn without the risk of breaking them. So loosen all 4 of the primary throttle plate screws about 1/4 turn. Then close the throttle all the way and wiggle everything around until the plates seat and seal in the fully closed position. By wiggling and jggling things around, the plates will center themselves up in the bores, and you can achieve excellent alignment. Simply snug the 4 screw back up and try it out. Repeat as necessary to obtain smooth, non-sticking operation.

Rumpity Rump

Lars,

Thanks for the tips. Shes going into storage in a week, so ill have at it then. I appreciate it.

Rump :cheers:

Wrencher

The other posibility is a worn throttle shaft housing. Try the alignment, and while you are there, move the shaft up,down, left, right and see if it moves around. Very common to see these worn to the point where you would see the throttle hang. A good machine shop can put bushings in for you.

Hans

Tom454

RE: The worn throttle shaft bores- don't mistake "end-play" for a worn throttle shaft housing. The shaft and discs are supposed to have plenty of end play. As mentioned, it is the up/down and side/side clearance that must be checked. Before you loosen the screws, check for excessive throttle shaft/bore wear. If that is okay, then go on to loosen the screws and adjust the discs.

PS- I am one of "those" people that repairs worn throttle shaft bores by machining the bores and installing bushings.

drspencer

I have a '71 350/270, 4-speed, no AC, completely stock, that has the same problem.

I recently had the carb completely rebuilt.

When installed, the throttle linkage won't 'kick down' all the way, and make contact with the speed/idle screw. There is a small space between the throttle linkage and the screw.

It idles at ~800 RPM until you blip the throttle with the pedal, or your finger, then it rests at the desired 600 RPM (the small space between the throttle linkage and speed screw now being gone).

It will do this every time, regardless if the throttle cable is connected/disconnected, choke connected/disconnect. Using a larger/stronger throttle return spring does nothing.

With the carb uninstalled, in your hand, the linkage is smooth and fluid, with no binding.

It should be noted that this problem only happens when the car is running. With the car off, the linkage completely returns. With the car running, it does not.

The car has perfect vacuum, with no leaks anywhere.

Any suggestions?

Thanks

toobroketoretire

Does your carburetor have a fast idle solenoid on the left side? If so that could be what is holding the throttle slightly open.

drspencer

That doesn't seem to be the problem.

It has a choke pull-off, but no electrical solenoid.

Thanks