Idle mixture settings on a dual carb set-up

Joe H touched on several important points, but I have some questions, the answers of which might help.

You mention a 1940 Master DeLuxe. These came with a 216. Do you still have the 216? Joe mentioned the importance of both carbs being identical. WHICH W-1's are you trying to use? Carter made 128 different type W-1 carburetors.

As to setting the idle mixture? Don't know, it would depend on which carbs you are trying to use. The adjustment range on the W-1 is not a constant different versions used different settings. SOME OF THE W-1'S HAVE AN INVERSE IDLE CIRCUIT! In other words, turning the screw in is RICHER; turning the screw out is LEANER.

There are several possibilities which may cause the surge below 2000 RPM; one of which might be the carbs are too large if you still have the 216. If the carbs are too large, the venturi air velocity would be low (this also could be a factor in trying to use the Uni-Syn) which would create a lean mixture unless the throttle opening was high enough to have the metering rod off of the thickest step.

Without knowing exactly what engine you have, and which carbs you have, I would be guessing to try to offer solutions.

I can't help you identify the engine, not in my field of expertise; but if the tags are missing on the carbs, call me and I can help you identify them 573-392-7378 (9-12, 1-4 Mon-Tues central time).

Jon

 

A bit more information on the Carter W-1:

This is my personal favorite single barrel carb for multi-carb use on inline engines. There are 3 major reasons for this:
(1) The versions I use/recommend are fairly common as are parts
(2) The W-1 has a mechanical power circuit (that means one does not have to hand-wind vacuum springs)
(3) The W-1 came with a leather accelerator pump (one does not have to worry about ethanol)

But for someone wishing to use these, below is some additional information for selection:

Carter produced 128 different type W-1 carburetors for use on a lot of different makes from 1932 through 1949. Without spending a lot of time explaining why, please accept that for the hotrodder, the most useful of these are:

420s - 1939~1940 Chevy
483s - 1941~1942 Chevy
574s - 1946~1948 Chevy

The other 125 different are best left to restorers!

As has been pointed out in this thread, carbs should be matched exactly by tag number and calibration. There is an exception to this. If one chooses the 483s and/or the 574s, these two numbers may be mixed/matched. If the 420s is used, all carbs on the manifold should be 420s.

All 3 of the above are S.A.E. size 2 (2 11/16 center to center mounting pattern), and have a main venturi of 1 1/4 inch. These flow APPROXIMATELY 195 CFM on the 1 and 2 barrel scale, which when converted to the 4 barrel scale is approximately 140 CFM.

There are two "issues" with these W-1's:

(1) plugged idle circuit cross-passage.
(2) worn metering rod/pump actuating linkage.

(1) If one examines the W-1 idle circuit, one finds that the fuel intake in the bowl feeds the idle jet, and fuel exits the idle jet into a vertical passage, intersecting with a cross-passage, and then down to the idle mixture screw/discharge port. The cross-passage is small, and the carburetor is cast iron (rust). About 75 percent of carbs which have been unused for several years will have this passage blocked. The "lazy" rebuilder can attempt to blow compressed air through the passage made available by removal of the idle jet. Air should come out at the idle mixture screw/discharge port. If not, one should locate the "soft plug" (both copper and aluminum were used) that seals the access to the cross-over passage, and using a small drill bit and compressed air, clean the passage, and install a new plug. The serious rebuilder or professional will just remove the plug, clean the passage and install a new plug.

(2) If one examines the back side of the throttle shaft, one will find a sheet metal bracket held on by a single clamp screw. This sheet metal bracket has a round (at least is is supposed to be round) hole, with an "L"-shaped rod attached. This rod, after making the 90 degree corner of the "L" goes vertical, and connects with the cross linkage which controls the metering rod opening and the actuation of the accelerator pump. After years of use, the rod wears the hole oblong, and the bracket wears a groove in the rod. IF THE PARTS ARE WORN, there will not be a 1:1 movement of the metering rod/accelerator pump with the throttle butterfly. So the throttle butterfly can be opened a certain amount, depending on the wear, without increasing the fuel flow. The engine may hesitate, and will certainly go lean until the slack is addressed by further rotation of the shaft. The bracket and rod are readily available, and not expensive.

One may find a copy of the original Carter service document (published with authority from Carter) here:

https://www.thecarburetorshop.com/Service_Carter_W-1-late.pdf

There are other issues, some significant, some just expensive, with the other 125 different W-1's.

Hopefully, some of the above may be useful to the OP until such time as he identifies his engine, and the carburetors being used.

Jon

 

Yeah Jon you hit it right on with want you said about the carbs, got them as close as I think I can I'll be hitting a few swap meets looking for a couple of W-0 carters or a match for the W-1 I'm running now. Thanks again

 

The W-0 carbs will perk up the engine in the lower RPM ranges a lot; but they will require adapters.

The mounting pattern of the W-1's is 2 11/16 inches.
The mounting pattern of the W-0's is 2 7/16 inches.

For those following this thread:

We took the issue to telephone.

We determined that the carburetors are not a matched set, one is a 420s, the other is either a 483s or 574s. This is probably why the Uni-Syn is difficult to make work. Since he has the system, the OP is going to try to match one or the other, and then adjust as best is possible. Matching one or the other is not difficult, as the W-1's are as common today as 97's were common 60 years ago.

Once this is done, see if the system is livable as is, or if he needs to replace the W-1's with W-0's.

Jon

 

Not single barrels but a unisyn is your friend and if you enlarge the photo to the unit you will see a good setting for an engine idling on both carbs. Every year I check them and have rarely made an adjustment in 7 years.

 

I've been thinking about it , the rear carb needs rebuild as it leaks and as I just got the car last year and plan to leave it to my kid I think I'll spend the money for 2 W-0 carbs and get it right. Jon you said that I'll need adapters to mount them ,do you have them or know where I can get them? thanks again!

 

Call me.

I will explain how you can make them (save money), or there is a work-around.

Jon

 

ok thanks i'll call you monday

 

I'm looking at carbs on ebay and they have a few carbs for sale, I'm staying away from ones from china they are a couple being made now saying new production bayword, thundermingo and motorretrocraft are a few of the names and wondered if anyone has used one of these and what are your thoughts on them.

 

bought 2 W-0 carbs supposed to have been rebuilt coming by this weekend I'll keep you posted on how I do.