WCFB woes revisited

[Don Izzo]

I got my WCFB back from the carb shop after his third attempt to correct the idle problem. As you may recall the idle hangs up a few hundrew rpm off the idle stop position if I slowly raise the idle or attempt to slow the car to a stop at a light or stop sign. If I rev the throttle peddle quickly the idle will settle back down. If I turn off the car I can watch the carb throttle lever settle back down on it's own. Looks like a vacume problem to me. Note that the condition exists with the throttle and trans. linkage connected or not. The last attempt at repair was to change out the throttle plate and instll a new throttle rod. Still not improvement. They are now asking me if it may not be something with the motor. The engine just got a fresh rebuild by a local rebuilder (with a very good reputation). Block was bored .030 over the rest of the motor is stock. All of the vacume hook ups are stock and intact with no leaks. The rebuilder of the carb is now refusing to believe it's the carb. I am at a loss. What else should I look at.
Don

[John M.]

Re: WCFB woes revisited

Don,
Since the throttle closes when the engine stops, I still think that it indicates the throttle return spring is not strong enough or the throttle plates are being pulled down into a bind with either the gasket or manifold.
I would double check the alignment of the carb base with the gasket and manifold. I bought a generic gasket a while back that did not line up well at all with the throttle plate bores. This could not be an engine problem.

Regards, John McGraw

[Duke W.]

Re: WCFB woes revisited

A similar situation can occur with the AFB and the cause is throttle shaft bore wear. You said the throttle shaft was replaced, but what about bushing the worn bore? A heavier spring can rectify the situation temporarily, but it probably just causes accelerated wear, and it will reoccur.

With a worn bore the throttle will come back to a slightly different position depending on how quickly you let off, and this will vary the flow area, which will cause an inconsistent idle speed.

With many of these Carter carbs now 40 or more years old, a lot of them probaby need the throttle bore bushed and machined back to OEM spec.

Duke

[Don Izzo]

Re: WCFB woes revisited

Duke...I have been told by the rebuilder who works for Chicago COrvette that you can not bush the throttle plate. I spoke to Bob Kunz who states you most definately can. The rebuilder found what he said is a good replacement throttle plate, installed a NEW throttle rod, tested it on his wet bench and returned the carb to me pronounced cured. Well that was not the case. I can get the carb throttle to return if I increase the return spring tension to the point where I have to really push hard on the gas pedal just to get the damn thing off the idle stop!! Chicago Corvette said they would replace the carb for another, and I am waiting to here from the rebuilder hoping to get an idea when I might see it.
Don

[Duke W.]

Re: WCFB woes revisited

I don't think Carter considered rebushing the throttle shaft bores as a field fix, but then they didn't design their carbs to last 50 years. The throttle shaft bore problem might be a little worse on the AFB because it's alumiumin, and I recall that the WCFB has a case iron base that holds the throttle shafts.

Several carburetor restorers, not rebuilders, have figured out how to correct this problem by renewing the throttle shaft bores. It's not inexpensive, but without new carburetors available, it's the only way to restore them to as new performance one the bores wear and cause uneven idle.

One thing you might try is wiggling the throttle shaft. With a good, snug fit of the throttle shaft in the bore, there should be little or no play, but it's tough to determine if it's too much unless you have a brand new carb available for comparison.

Duke

[Jon S.]

Re: WCFB woes revisited

Don,
Your not alone! I've had this same problem with my wcfb. I've sent it out west, I've sent it east, I've taken it to a restorer and I've take it to a local carb guru. I've heard all kinds of responses that led me to believe the problem was behind me. Still have the problem! It's been a year later. If you ever solve this please e-mail me. I'm ready to box it for the next guy and get something that works! I do agree with most of the suggestions you have recieved. I just
haven't been able to get any of them to work for me.
Regards,
Jon
P.S. A heaver return spring is not the answer

[roy braatz]

Re: WCFB woes revisited

It sound to me that your metering rods are out of adjustment, warm up the engine ,remove the front metering rod cover while the engine is runing at your high idol, then push down on the metering rods, if the RPM lowers the metering rod adjustment is off. If so Re-adjust, or the metering rod piston spring is to long fighting the vacuum pull down on the metering rod piston.Hope I made this clear to you.

[roy braatz]

Re: WCFB woes revisited

I also meant to add that you need to loosen the metering rod stop screw when you have the cover off to be sure the rods go down all the way when you push them down.