Frustration continues-Will not idle at operating temp

[dplotkin]

(56-60) We have put a high quality kit in the carb (WCFB) and today swapped out the intake manifold, and she still will not idle hot. She starts cold fine, purrs like a kitten and then, as she warms up she looses it & begins a lean roll until finally she will not run at idle. Choking the carb with your hand brings up idle speed, just like a vacuum leak. Seems we have ruled out everything but the carb. We put a USA Parts supplied replacement WCFB on it but that carb showed up with a bent choke assemby & wouldn't respond to any adjustments so I returned it. They will exchange only, so they will be sending me another one. Meantime it looks as though we have ruled out a vacuum leak, runs exactly the same with the new manifold.

My mechanic is highly skilled, says idle circuits must be screwed up even though he cleaned it & put a kit in it. Should I send my carb to someone or put the second replacement carb I'll be getting & take my chances?

[The Tassie Devil(le)]

I am agreeing with your mechanic.   

By artificially choking it, tells me that the engine is running very lean at idle when hot.

Got to be something either with the Idle Circuit, or a Vacuum leak that you cannot see, or hear.

Have you tried running it with all the vacuum lines removed?   

Have you checked the operation of the Vacuum Advance diaphragm in the Distributor?   Is the Distributor behaving correctly?

Bruce.

[dplotkin]

Had distributor set up on a machine, it is fine. That she smooths out when choked seems to rule out spark. Previous to replacing intake we pinched off all vacuum lines & sprayed carb cleaner/ether everywhere looking for a vacuum leak and found nothing. To rule out a cracked manifold we replaced it, car behaves exactly the same way.  What goes wrong in a carb (with a fresh kit in it) to run fine until the engine warms & the choke opens?

Dan

[The Tassie Devil(le)]

One of the IdlePpassages internally blocked.

Wrong Idle Screws.

Bruce.

[dplotkin]

I guess I'll try the second replacement USA Parts Supply is sending & if that doesn't work I'll send the one I have out for a total redo. Thought I'd be able to use it before the snow comes, but alas it is not to be.

Thanks for the help.

Dan

[Dave Shepherd]

Try this get a Bernzomatic, take out the orifice, get a piece of hose on the tip, turn the bottle on and stick it down the carb secondarys if the engine picks up, if so,  the rear throttle is not closed, if ok continue around the manifold to head surfaces and so on, see the  engine changes doing this.

[dplotkin]

Weve done that using eather around the manifold looking for vacuum leaks because that is how it behaves (12 HG's only-should be 17-18). That is why we changed manifolds. If you choke it with your hand, it bounces back & smooths out. I'm wondering if a timing chain...valve timing could be the source of low vacuum.

Dan

[Dave Shepherd]

If it jumped ( unlikely) the timing would change and you would detect that timing the engine.  The WCFB on a car I recently worked on has a similar issue, it was the carb secondary throttles not quite closing that is whay I suggested that test, but I see you have had 2 carbs do the same thing.  That carb has multiple float adjustments, you must follow the book closely.  Did you try down into the carb secondarys to see a change, if so the throttle plates are not shut, repeating myself, sorry.  If the carb is off  shine a lite in the rear bores and see if it shows thru the throttles.

[dplotkin]

We did not have two carbs do the same thing. We tried a "rebuilt" carb from USA Parts & it was junk out of the box, wouldn't run cold, when mine runs beautiful cold. So I sent that back, put a kit in the carb & same symptom. Changed intakes, same symptom.
Vacuum needle steady as a rock, doesn't suggest a valve timing issue. Our theory is debris in the dead-end passages that require a professional job, something more than a kit. Secondaries are closed, problem doesn't show itself until the choke opens & the mixture leans. Looks like an old fashioned lean roll, so we are going to slap my friends known good carb from his 58 Fleetwood & see if we are right. If so, I'll send the carb out to be completely done (it still has the factory plugs in it). Or maybe I'll get lucky & the USA carb they are exchanging (no money back on carbs, be forewarned) will be good enough to use. If it isn't the carb, I'll consult a priest, because we don't know what else it could be.

Dan

[The Tassie Devil(le)]

Now, timing could be a problem, seeing as when running with the choke on, and engine revs increase, the timing is being automatically advanced.   Or is that the case?

If it idles smoothly, at idle speed, with the choke on, it is definitely running lean.

Bruce.

[dplotkin]

That's what she does, runs like a new car with the choke on. Previous owner said he had a contaiminated fuel system, also had the fuel filter in wrong allowing junk to bypass it, so we believe we have a carb with fouled idle circuits.

[dadscad]

Does the WCFB use the stainless shim directly under the carburetor, like the AFB Carter on the later models? If so, is yours there? They will not idle correctly with out it.

HTH,
David

[dplotkin]

Hmmm, I'll have to consult my repair manual.

Dan

[The Tassie Devil(le)]

How could we all forget to make mention of the Stainless Steel Shim.

Our memories must be going bad.

Bruce.

PS.  I have an excuse.

[John Washburn CLC 1067 Sadly deceased.]

No the shim is not used on the wcfb, it was used when they changed to AFB.

The Johnny

[Dave Shepherd]

Correct, the shim prevented heat soak on the aluminum bodied AFB, the WCFB did not have an issue with that.