1 x 4 Carter WCFB, 1959

[Jorn J.]

Hi
I think there is a problem with my new restored Carb.Nothing happens when I set the 2 Idle mixture srews in front! I have only 0,50 Co2 in Idle(450 rpm) and it doesn't matter if I turn them 1,5 turn out or 4-5 turn out the Co2 is the same
I think that it should be higher in Co2 and the car are loosing power when I try to drive?

Jorn/Denmark

[Jack H.]

Re: 1 x 4 Carter WCFB, 1959

"I think that it should be higher in Co2 and the car are loosing power when I try to drive?"

Remember, a typical 4 Bbl carb is actually THREE discrete carbs in a single package. One section of the carb functions ONLY during engine idle condtions. Then, as you increase RPM, the carb switches from it's idle circuit to its primary circuit. There, the primary jets govern mixture.

Finally, under extreme RPM demand, the carb opens its secondary stage and those jets (plus the primary jets) dictate the overall air/fuel mixture. So, when you're actually driving the car, the idle circuit is inactive...

That doesn't mean you shouldn't want to go understand why the freshly rebuilt carb you just bought doesn't exhibit a response to idle circuit mixture adjustment under bona fide idle condition though!

[Jorn J.]

Re: 1 x 4 Carter WCFB, 1959

Hi Jack
Thanks for answering!
Have I understand You right that the 2 screws in front only are for Idle mixture and not for higher rpm/driving!
If that then I have to look on the ign. setting/timing!
The last 2 lines you wrote, please write it again in other words because it was difficult to understand for me

[Jack H.]

Re: 1 x 4 Carter WCFB, 1959

Have I understand You right that the 2 screws in front only are for Idle mixture and not for higher rpm/driving!

Yep, crack any 4-Bbl carb book that describes theory of operation and you'll confirm...

If that then I have to look on the ign. setting/timing! The last 2 lines you wrote, please write it again in other words because it was difficult to understand for me

So, when you're actually driving the car, the idle circuit is inactive...

When driving (car in motion going down the road), engine RPMs are above the idle threshold. So, the carb's idle circuit is NOT working...the carb is running on its primary circuit (the front two jets/rods) and THAT section of the carb dictates air/fuel mixture.

If I removed the hood, and 'strapped' you across the radiator with a screw driver in your hand, you'd find that turning the idle mixture screws had NO EFFECT on the air/fuel mixture while the car was in motion driving down the highway.

Is that more clear?

That doesn't mean you shouldn't want to go understand why the freshly rebuilt carb you just bought doesn't exhibit a response to idle circuit mixture adjustment under bona fide idle condition though!

This says you paid good money for a carb that was supposedly 'restored'. The idle mixture needle valves OUGHT to work when the engine is sitting, hot, at idle RPM. You SHOULD be able to turn them and observe change(s) in RPM as they alter the air/fuel mixture ratio.

So, I'm telling you something's wrong from your report that turning the screws did NOTHING... And, I'm telling you those screws only affect the air/fuel mixture with the engine at idle. You had expressed a fear that if they weren't working, the car would run improperly at highway speed(s)...

The basic operation of a 4-Bbl carb made in America isn't appreciably different than one made in Europe. They all have separate 'circuits' inside that work (become functional) at different engine RPM ranges.

That's because you can't get a full range, across the board, uniform air/fuel mixture from a SINGLE venturi geometry. So, the carb has different effective venturi circuits that operate at different RPM ranges.

[Jorn J.]

Re: 1 x 4 Carter WCFB, 1959

Hi Jack
That was clear speak for a Dane. I don't think its allowed to do that with the strap and screwdriver
In meantime I have split the Carb and found out that it was painted inside with the same type of paint as outside(Yellow/green) and this paint will not work together with gasoline so I haved cleaned it and blow it with air and then I wait for a new gasket and then I will try it again.
Then I hope that the mixture settingsscrews are adjustable.

[Clem Z.]

Re: 1 x 4 Carter WCFB, 1959

if the butterflies are open to far to get the idle speed the idle/air adjustment screws will have no effect as you are idling off of the idle transfer slot