Question: How far gone can a WO carb be to consider rebuilding it? Rusty...

[squidtone]

Hi,
My CJ3A sat in woods for a few decades I think. The engine was frozen, and the WO carburetor was frozen too. I got another engine and it came with a Solex. For the most part I've been quite happy with the Solex. The only negatives I think are the sensitivity to fuel pressure (I keep it at 1.5 PSI with a Holly regulator) and tendency to empty out after a few days sitting requiring 15 seconds of engine cranking to fill it up before it fires). (That's the most annoying thing).

I'd like to get a WO on there.

So, of course, the WO has a cast iron throttle body (I guess that's what it's called) and a cast zinc upper body.
The upper body is in good shape and I think will respond well to a rebuild.
BUT,
The cast iron throttle body is rusted. The main shaft is frozen in the body. I tried penetrating fluid for many days. I gave up. Someone before me bent up the butterfly inside I guess from trying to free it up. I broke the screws off getting that throttle plate off.
I have no problem making a  new throttle shaft, but is it even possible to get the old one out? Is something this rusty worth making an attempt to save? Are there passages that are now no good due to corrosion? Is it a waste of time to mess with it?
Can I use propane heat to blast the body to free up the shaft? Is that a no-no?

I don't mind putting in labor...I have a machine shop I can use to make parts, but if experience of others says they cannot be saved, I'll move on.

Hope to get some input...

Thankyou!
Dave

[scoutpilot]

I've resurrected worse. My greatest concern would be with the valves and jets inside the bowl housing. The threads inside the Zamac (Zinc/aluminum alloy) body may be too brittle to save without very careful treatment and extraction of the brass parts. Even using correctly-sized screwdrivers, trying to force them will often end up with stripped slots. The worst-case scenario involves a drill press, heat, penetrating oil, and EZ-outs to remove them.

[squidtone]

Scoutpilot,
Thanks for the input. Good to know. I'll take apart the bowl casting and see how far I can get with those threaded parts.
I will use some light heat on the shaft of the main body and see if I can loosen up the shaft...

I rebuilt an Allis Chalmers Zenith carb (cast iron) some years ago and I was able to remove all the threaded jets and stuff. I was shocked I was able to rebuild it, but it wasn't frozen like this one, hence my questions about it.

I'll report back.

[squidtone]

Positive developments:
I got the shaft out of the throttle body. It was a little embarrassing how easy it came out, although I wonder if sitting for a couple years after being doused with penetrant helped. A little heat and it broke free and came out. I had to grind the remains of the throttle blade screws to slip it out.

I also was able to take apart the rest of the carb and all the screw caps and inner brass parts came out. (Not shown, but they all came free.)

I am pondering how to re-do the throttle shaft...I didn't realize it's steel. I would consider re-using it, but the bracket at the end is moving on the shaft. I guess it's a double "D" shaft end with the bracket fitting over it, then it's peened over.
I looked online to see if parts are available new, and I don't see anything that matches. I'm thinking I'll get a piece of steel rod, and make a duplicate shaft I can try to make a duplicate double "D" and peen the old bracket on.
I'll clean everything and see how big the throttle shaft bores are.

Dave

[scoutpilot]

The shaft is actually Nickel-Brass. .3125" in diameter. Check for runout. Measure in more than one position of the rotation of the shaft. Bores in excess of .313" and a shaft, measured at both ends, in the center of the unmilled portion, less than .310" will require bushings and a new shaft. NOS, or New reproduction shafts for anything except the WO 539S are unobtanium. Except for those of us who mill our own.

[squidtone]

Scoutpilot, Thankyou for the additional input. Of course now that you mention it, it seems crazy the shaft would be steel. But there is heavy corrosion (pits) on the section where the throttle blade resided. I suppose the "trash" (acorns, seeds, n' stuff deposited by rodents) that sat there for years corroded even the normally low corrosion nickel/brass.
The shaft ends that reside in the body are around 0.3075" up to 0.309".
I'll use gauge pins at work to check the bores, but I expect they're worn beyond spec.
I have to think this through to be sure I have the "chops" to execute making new parts; I expect I'll have to make a shaft, and source a new throttle blade.
Well, I feel pretty good I at least got the carb taken down to it's elemental bits with not too much damage.
Thanks
dave

[scoutpilot]

You probably noticed that the shaft is now egg-shaped. The bores are likely to be the same. Rotating the shaft opens those insidious little gaps called vacuum leaks. You'll need to inspect the backside bore for the thickness of the metal around the bore. Many came out of the production process with an off-center, yet perfectly functional passage. But this often led to a one-time, non-rebuildable service life. Boring can cause the metal to crack and break off.
Getting past that, you'll need a milling machine to do the work on the bores and shaft. Drill presses and bits are too wobbly.
Alignment for the bores is critical. Using a 3/8" six-flute reamer works best. Take your time. Do not bore all the way through. Through-boring will leave a gap around the shaft inside which disturbs airflow and causes severe idle issues. The only cure for that is multiple bushings which have to be trimmed for a smooth interior wall.  A .495" maximum depth will leave a thin lip against which the bushing will seat. Install the bushings using a through bolt, pulling them in. Then ream the bushings, all the way through from both ends with a four-flute .3125" hand reamer.
Later we can talk about milling the shaft.

[squidtone]

Scoutpilot,
I appreciate your valuable experience here.
I believe I understand your first point: I basically should machine counterbores for sleeves. Do not bore all the way into the "throat".
The parts I have are indeed egg shaped.
I own a nice old precision bench top CNC, and I also have access to a Bridgeport. I have some Starrett indicators, and I have the tools I need I think. (I may have to order a couple things...working on it). I'm not a "machinist", but I've been machining for a few decades as an amateur. I will think about making a fixture to mount the casting and get the shaft bores coaxial with the machine.
First of course I'll assess the feasibility of sleeving the casting (how much meat is there).
I'll report back.
Thankyou

[scoutpilot]

If you have any more questions or concerns, call me 336-963-3605, 0700-1900, seven days a week. Good luck!

[squidtone]

That's very kind. I appreciate it. When I come up with a plan of attack I'll probably pick your brain.
I used some gauge pins to determine that I could get a 0.314" pin in the bore. Not terrible I guess but of course that doesn't measure if the bore is egg shaped.
You mentioned that some of these castings have the throttle bore offset from the boss, and indeed, the one I have has the bore very close to the edge of the boss. There is only a 0.050" wall thickness at the thinnest. If I want to bore out the boss for a 0.375" bushing, I think the resulting thin wall of the boss after boring will be too thin.
I'm wondering if I should bias the position of thetoward the center of the boss, then drill the throttle bore in the correct location. I'd have to press in a solid piece of (insert type of material here) and then bore the throttle shaft hole. The bushing will be quite thin at that thin side of the boss, but that's the compromise.
Is brass ok for bushings?

[scoutpilot]

I wish you good luck with the plan of attack. Bushings are available at https://www.carbjunkys.com