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Carter WCD Experts Chime In!

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Stingray View Drop Down
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    Posted: May/29/2023 at 12:56am
Hi, Looking for help.

1966 Rambler Rogue 232 six Carter WCD 3888S two barrel, Automatic.

Poor fuel economy, rich cruise.  Carb rebuilt, float level set. Idle screws adjusted and engine stumbles if screwed in further.  Vacumeter piston adjusted and pulls all the way in with vacuum.

Measured with Innovate LM-1

A/F 13.5-13.8 at idle. (OK)
A/F 11.9-12.5 at cruise, light throttle or deceleration at any speed 30-55mph (RICH)
A/F 13-13.5 on medium acceleration (Probably OK)

Any suggestions on what to investigate or test further?

Things I probably need to check are ...
  • correct operation of heat riser valve?
  • vacuum leak?  Wipers (no power brakes)
  • Vacumeter piston travel and completely bottoming? (I cleaned bores and checked during rebuild but you never know!)
Prior to rebuild I was getting 12mpg.  I don't think it's any better now and the rich cruise figures are a concern.

Any thoughts and assistance welcome!

Will keep you posted on progress.

Beer,
Joe

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Stingray View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Stingray Quote  Post ReplyReply Direct Link To This Post Posted: Jun/05/2023 at 2:10am
Update ...

Checked fuel pressure - around 4-5psi so good there.

Clamped line to vacuum wipers, made no change while idling.

Checked free movement of exhaust heat riser.

Removed carburetor top cover.  Checked air bleeds clear and correct cover gasket.  Rechecked and set floats at 1/4".  Leaned out idle mix to 14-14.5 A/F ratio.

On test drive, no real improvement but noticed pronounced stumble on hard right turns at low speed with throttle closed.  A/F ratio very rich at 10-11 while this is happening (flooding?). 

Still suspect float bowl fuel level.  There is no sight plug to verify actual levels.

Any suggestions?

Beer
Joe
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wittsend Quote  Post ReplyReply Direct Link To This Post Posted: Jun/05/2023 at 11:11am
My first guess would be the fuel pressure is too high. Some carburetors just can't stop the flow. Idle is OK because the volume of fuel is low but at a certain point as the pump is more active the needle and seat are getting overwhelmed by the shear volume and pressure. Some carbs have issues over 2.5 pounds. So, as an example if you were getting 2.5 pounds at idle but going to 5 pounds as speed increases that is doubling the pressure.

 In my Corvair world the 2-4 pound electric fuel pumps are typically OK, but the 4-7 pound pumps cause problems. A few pounds doesn't seem like much compared with EFI cars running in the 50 pound range but if that doubled pressures would be in the 100 pound range! Likewise the doubling in a carb situation with just a few pounds is parallel. It seems you have done everything else reasonable to solving the problem.
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Stingray View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Stingray Quote  Post ReplyReply Direct Link To This Post Posted: Jun/05/2023 at 7:23pm
Hi wittsend,

Thanks for your thoughts on fuel pressure. In my case seems to be 4psi at idle and high RPM.  But I'll keep an eye on it.

I'm wondering about the lateral adjustment of floats and whether it is critical, mine seem ok but haven't double-checked.

The stumble/stalling on sudden slow right turns with throttle closed and reading very rich keeps me thinking of fuel level.

Does anyone think that installing a sight plug is a good idea and should I use the location where there is already a boss on the bowl?

Cheers,
Joe
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post Posted: Jun/06/2023 at 12:08am
One of the floats could have filled with fuel and become a sink. Better check those floats out carefully. Shake them and listen for fuel sloshing. 

An internal gasket could be leaking. Wrong gasket or warped housing. 

There is more to the metering rod adjustment than just the vacuum piston. There is a throttle linkage adjustment as well. The metering rods are moved by both the throttle linkage and the vacuum piston.


1955 Packard
1966 Marlin
1972 Wagoneer
1973 Ambassador
1977 Hornet
1982 Concord D/L
1984 Eagle Limited
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Stingray View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Stingray Quote  Post ReplyReply Direct Link To This Post Posted: Jun/06/2023 at 1:16am
Hi and thanks for your input! Much appreciated.

I'll check the floats again.  I believe the "Vacumeter" system is working correctly and set up as per the TSM.  The rods move up with throttle and pulled down against the spring with vacuum.

The fact that the mixture is very rich on deceleration or light cruise suggests a problem the the low speed circuit. 

I haven't checked for any warpage but gasket is new and appears correct.

Will keep you posted.

Cheers,
Joe
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hurst390 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/06/2023 at 12:23pm
When you rebuilt the carb did you use a tomko kit?
If so those kits use a proprietary needle and seat assy. Total garbage. I use Standard Hygrade carb kits on most oem carbs.
SC/Hurst Rambler

11.62 120

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Stingray View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Stingray Quote  Post ReplyReply Direct Link To This Post Posted: Jun/06/2023 at 8:42pm
Hi Hurst390,

Not many choices here in Australia.

I'm using a Walker Products kit made in the USA.

Part # 15385

Hope it's a good one!

Beer
Joe
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Heavy 488 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/07/2023 at 7:47am
Over the last couple years I've used a few walker kits on Motorcraft and Carter AFB's and they were good.
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Stingray View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Stingray Quote  Post ReplyReply Direct Link To This Post Posted: Jun/09/2023 at 1:52am
Hi All,

Just a quick update.  

I've dismantled checked everything and rebuilt the carb again.  No real change on the test drive. Rich cruise and deceleration.

So I investigated the hard slow first gear right turns.  This results in almost stalling/flooding and A/F down to 9:1.

The same does not happen on left turns, in fact it leans out a bit to 13.5:1.

My theory is ...

The low speed jets are in wells on the left side of the carb and the fuel on that side of the carb rises on right turns causing the rich condition.

My plan is to set the floats at 3/8" instead of the current 1/4" and see what difference that makes.

Any thoughts welcome.

Beer
Joe
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