Carter carburator parts

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Scoutpilot
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Re: Carter carburator parts

Post by Scoutpilot » Fri Jan 01, 2016 3:22 am

I don’t doubt your findings wo2jeeper. I don’t recommend bushings or a shaft unless warranted. Just remember that both the shafts and the bores will wear into egg-shaped ovals. Not so pronounced as can be seen with the naked eye, but measurable. The best way to determine if bushings and/or a new shaft is warranted is to use a micrometer. Don’t perform just one measurement in one spot. Choose a point on the shaft where it passes through the bores. Take four separate measurements, ninety degrees apart. If you have a small bore gauge, perform the same test on both bores of the throttle. Then do the math. In my experience, a gap of .005” is a vacuum leak.

Huge caveat! Before anyone decides to go out and disassemble his throttle take note! The tiny brass screws that hold the throttle plate to the shaft need to be checked visually before applying a screwdriver. The tips, where they protrude from the back-side of the shaft have probably been split or peened over. An attempt to remove the screws will undoubtably yield broken screws, which will yield several bad words from your mouth. If you have a means of shearing the protruding tips without severely damaging the throttle itself prior to screwdriver application, please employ it first.

As well, after you place the screwdriver in the slot use a small hammer and tap the screwdriver, firmly but not hard, a few times to break the corrosion on the threads of the screw.
'70-'71 'A' Batt., 377th FA, 101AB
(Slicks and LOH's)(Col's LOH Pilot)
'71-72 CHARLIE TROOP,
16TH AIR CAV, 1ST AVN BDE (AEROSCOUTS)
LOW LEVEL HELL.
'46 CJ2A
'47 CJ2A
'48 CJ2A
'48 B1PW126
'69 CJ5


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wo2jeeper
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Carter carburator parts

Post by wo2jeeper » Fri Jan 01, 2016 4:19 am

Scoutpilot, I am an experienced rebuilder. The only thing I see here is that you give the common things you meet during a rebuilt of a carburator as heavy issues. This is just to share knowledge. Let everybody do their own and help with advise. If anyone needs the 3-48" throttle plate screws in brass with slotted head I have enough though ;-)

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Scoutpilot
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Re: Carter carburator parts

Post by Scoutpilot » Fri Jan 01, 2016 4:36 am

My friend I do not doubt your expertise. You and I have plenty of experience and lots of spare parts on hand. I only need to harken back to the very first screw I broke because I didn't know to check. I was heartbroken. With no spare carb or parts or tools or skill to repair what I had ruined. I'm reminded of the poem which starts out, "For want of a nail...".
'70-'71 'A' Batt., 377th FA, 101AB
(Slicks and LOH's)(Col's LOH Pilot)
'71-72 CHARLIE TROOP,
16TH AIR CAV, 1ST AVN BDE (AEROSCOUTS)
LOW LEVEL HELL.
'46 CJ2A
'47 CJ2A
'48 CJ2A
'48 B1PW126
'69 CJ5

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Chuck Lutz
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Re: Carter carburator parts

Post by Chuck Lutz » Fri Jan 01, 2016 9:32 am

Can't find the doc right now Scout, but I seem to remember that 0.005" is the allowance on the bore/shaft assembly. Remember also that what the situation is with parts, rebuilds, etc. in Europe is not the same as here in the States. Here we see jeeps driven til they drop and that includes clutch rods worn through til they break off as well as the kind of wear to the bore and the shaft on the Carter WO.

Many shafts were BRASS with a thin steel coating and then they were solid steel. My limited knowledge of metalurgy tells me that the iron flange body will WEAR more and WEAR faster than the shaft will and simply replacing the shaft may not do the job.

The egg-shaped wear you mentioned is what the carb builder in these parts finds most of the time and he bushes them to solve the problem. Oversized shafts are not in a large supply in my area so the solution to the problem is to bush the flange body to STOCK and use an original STOCK throttle shaft assembly.

Not to mitigate the the disagreement here...but the shaft is not AIRTIGHT in the bore for a reason....the flange body heats up and cools down. In Winter and under operation the temp of the iron can fluctuate a hundred degrees easily and that would cause the actual ID of the bore to change...if the bore did not allow for that change in ID the shaft would bind. The shaft is either clad brass or steel, both of which will be subject to differing shrinkage and expansion due to temperatures and at differing rates.

So...the design has some ability for a minute airleak when brand-new....the performance of the carb in being able to be idled down to maybe 600 RPMs is effected by how MUCH air can leak in to alter that 16-to-1 air/fuel mixture. With that in mind, how MUCH air that leaks in over time will begin to mess with the mixture over time...a slightly egg-shaped bore may not leak enough to make a smooth idle possible, but as wear increases between bore and shaft the fuel/air mixture will degrade and that makes it harder and harder to try to get it to idle down.

In other words....this isn't an instant problem...it's like getting old...you just can't run as fast over time and you slow down over time. The idea is to nip the problem in the bud....and if you are spending $20,000 on the project....bushing the carb you know NOTHING about isn't an issue to lose sleep over the cost on.

As a rule, given the appearance of the 539s carbs we find here (more than half don't even HAVE the 407 on them....and this air leak comes to mind as to why they don't) are pretty grungy and as a matter of preference when rebuilding them they are almost ALWAYS bushed. Call some of that "preventive maintenance" if you wish, but how one can tell if the bore is perfect or sorta/kinda/almost round isn't visually possible so the job is done almost as a part of a complete overhaul...

Hey, we spend money to balance the crank/pistons/rods these days and that is certainly a wise thing to do and may not be needed, but until you do the job you don't know....until you mic the bore in four areas on both sides as you suggest, you don't know if it needs to be bushed. Anything less than perfectly ROUND in my book screams BUSH THESE BORES!

You can bush it now or bush it later....take your pick!

You can mount that WO on a perfectly running jeep and if it won't idle down you KNOW there is leakage there!
Chuck Lutz

GPW 17963 4/24/42 Chester, PA. USA 20113473 (USA est./Tom W.)
Bantam T3-C 1947

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Scoutpilot
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Re: Carter carburator parts

Post by Scoutpilot » Fri Jan 01, 2016 10:13 am

I mean no disrespect for wo2jeeper. Chuck, you and wo2jeeper are correct. Chuck you are exactly right in that the allowable gap is .005”. New from the factory spec has the bores at .3125” ID and the shaft is .3125” OD. The air gap is minimal at new or newly rebuilt. Yes, early shafts were brass. Later shafts were Nickel/Brass and the last iterations are steel. Yes as well that we Americans do tend to run our equipment to death, bring it back and run to death again. While cats have nine lives, it seems our old Jeeps run a close second.
'70-'71 'A' Batt., 377th FA, 101AB
(Slicks and LOH's)(Col's LOH Pilot)
'71-72 CHARLIE TROOP,
16TH AIR CAV, 1ST AVN BDE (AEROSCOUTS)
LOW LEVEL HELL.
'46 CJ2A
'47 CJ2A
'48 CJ2A
'48 B1PW126
'69 CJ5

trifido
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Re: Carter carburator parts

Post by trifido » Mon Jan 04, 2016 5:19 am

Scoutpilot wrote:I’ve got a few 407’s. With ($75.00) or without bushings?($35.00)? Without bushings will require bushings.
P.M. Sent


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