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old-tank

Carburetor: WCFB 2197S idle problems

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Will not return to idle after "exercising" the secondaries.  Seems that the throttle plate for the secondaries hangs open just a little.  There is a return spring and that has even been replaced by a heavier spring.  I can manually move it closed with the engine running.  It will also close by itself if the engine is shut off.  Nothing seems to be binding when examined on the work bench; lubrication does not help.

This carb is sitting on top of a 264 nailhead in my 51 F-1 truck.  And NO, I cannot drive sedately avoiding opening the secondaries!

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Next time it is off of the rig, look at it closely from the bottom and see if the throttle plates could be hanging up on the bore due to throttle shaft wear (shaft not holding the plate centered as it closes). I don't recall ever having to fix that on a WCFB, but I have seen it on many other carburetors.

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Some of the early WCFB carbs had some weird secondary lockout linkage, that if not adjusted absolutely perfectly, can cause your issue. This included the linkage from the choke to the lockout. Do not remember if the Buick carbs used it, but Cadillac did. I have spent hours adjusting on some of the Caddy WCFB's to get them to function correctly. Worth a look.

 

Jon.

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I checked the carb on my other 3 cars and the linkage is the same.  The linkage is free when in the high idle situation.  Lateral pressure to the shaft will not free it...only rotating the shaft (or turning the engine off).  And I can't duplicate any binding on the bench.

Right now I am looking for a throttle body section.

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Is the throttle linkage holding it open? Dumb question, but if it's not binding on the bench, it could be that. 

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5 hours ago, Beemon said:

Is the throttle linkage holding it open? Dumb question, but if it's not binding on the bench, it could be that. 

Nope.  It is only the throttle for the secondaries.  Still testing.

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Maybe the secondary return bar is hanging up on the car somehow? If it comes off when the engine is turned off, it sounds like engine vacuum is keeping them open. There could be slack in the secondary linkage?

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Too bad you can't bench test it with a pressure differential and flow across the plates. Tom Toal, the famous GM carburetor engineer, told me carburation it not a science. It is an art. As an artist, I would bush the shaft. What has been lubricating that shaft for the last 60 years? Dusty unfiltered air?

 

Ben will tell you why 4005 is a velocity constant.

 

Bernie

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3 hours ago, 60FlatTop said:

Too bad you can't bench test it with a pressure differential and flow across the plates.

 

I think it would be pretty easy with a vacuum cleaner and some duct tape and then manually work the linkage. This is how we were going to go about comparing the flow of a cone cotton gauze filter versus a properly sized pleated paper filter but had difficulty figuring a way to use a flow meter... not really applicable in this scenario, just a visual inspection. 

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Yes, of course -- Duct Tape!!!  Dang, why didn't I think of that...?   :P

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13 hours ago, Beemon said:

I think it would be pretty easy with a vacuum cleaner and some duct tape and then manually work the linkage.

 

That's about a 500 CFM carb so you would need to had a hefty vacuum cleaner. Incoming air on environmental air systems is generally filtered at 500 feet per minute. That minimizes pressure drop and keeps the filters from getting sucked into the fan. 500 fpm means you need an effective area of 1 square foot. It would be hard.

 

MAYBE, I would disconnect the secondary linkage and run the engine while jiggling the throttle shaft and spraying volatile carb cleaner around the base.

 

On your other project a couple pitot tubes for averaging, Tygon tubing, and some water would make a good flow meter.

 

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Too hot to deal with now with temperatures starting at 80*f in the morning and spiking to 105 later all with dew point in the mid 70's.(too hot too soon).

Trying to get 2 cars ready for a trip to Colorado (driver plus a backup if issues late).

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Flow meter?  Why not look for a race engineering shop that flow benches cylinder heads.  Then mock-up an air cleaner base to it.

 

Back in the '80s, a magazine did a mass-test of air filter element flows and then the then-beloved K&N surgical gauze.  At that time, the Motorcraft paper filter came up with the best numbers of any paper filter and not that far from the "high-flow" K&N filter element.  Seems like there's an Engine Master video of air cleaner housings for power?

 

Found a deal from a Dodge Charger forum of flow tests of about 8 different water pumps for Chrysler B/RB V-8s.  Perhaps something of that nature for Buicks?  OR . . . at what flow spin-on oil filters start to bypass back to the crankcase?  Then position that against filter media size and efficiency at what micron level of foreign objects trapped by the media?

 

NTX5467

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