Late Carb (iron cast) help

[ducatti]

I´m puting my carb together and don´t know if the piston (vaccum?) has to float on the shaft or not (if not, I believe it is broken).
The small piston is holded on one side of shaft and the bigger piston (with grooves) is aparently floating in the other end of shaft.
Please see photos and let me know.

Thanks,
Ducatti

[John V Cliche]

Hi Ducatti ,
The shaft has 3 notches or positions is the piston latched into 1 of them?
If you have a new or nos rebuild kit there should be an accelerator pump in the kit.
You should have a little play between the shaft and both pistons to allow them to center in their bores but in order to pump the pistons should not move freely on the shaft .
I noticed the retainer plate that holds vac. piston in place but do you also have the spring that goes between the 2 pistons ?
Do you have the zenith manual?
If you would post the number code on the metal tag I might be able to give you the assembly specs for that carb.
Hope this helps.
John

[ducatti]

John,
Yes, the shaft has the 3 notches and I understood what you said about the piston that locks in the notch, but the other end, where the "big" piston goes, there is not to latch and it doesn´t look right to me...
I do have the spring but don´t have the kit or the Zenith manual.
The number on the carb tag is GM 2137474 - 10046

See a closer shot of the piston. Can´t see any broken evidence
Thanks a lot for helping me
Ducatti

[ducatti]

Can´t make the image work...

Would you please copy the link...

http://www.surfacezero.com/g503/data/50 ... haft_1.bmp

Thanks,
Ducatti

[John V Cliche]

Hi Ducatti,
I got your pic.
You really SHOULD be doing this reassembly with new parts.
What are using for gaskets ?
If you drop the shaft thru the vac piston from the top it should not go all the way thru and fall out the bottom if it does, stop right here IT IS BROKEN , if not then continue.
The accelerator pump assembly is made up of these parts
Put the shaft thru the vac. piston from the beveled end.
Slip on the retainer with the cup side facing the pump piston
You should have a collar that looks like a rivet with a hole thru it slide it on the shaft from notched end with the large end of the collar facing the pump end.
You need two springs 1 small ,when everything is ass. it should keep the vac piston in place but allow a little movement. The second spring ( large ) will fit between the retainer and the pump piston to keep the pistons tight or at least to each end of the rod.
Install the pump piston thru the banjo slot and latch it in place ( middle slot )
The above ass. should allow a little movement between the pistons to compensate for fluctuations in engine vac and fuel need.

Your carb model is 30BW11GM ( 10046 )
venturi #28
main jet #28
idle jet #14
power jet #16
acc. jet #13
well vent #16
pump strock 3/4 ( set the punp piston on the middle of the 3 notches )
fuel valve seat 40
float setting 1 3/8 inches

All the above info came from TM9-1826C from Portrayal Press.
You can get carb kits from U. K. or Can. or U. S.
You can get all the needed manuals from Portrayal Press
Ask if you need the contact info for above

Good luck Ducatti
Hope this helps
John

[ducatti]

Hi John,

I tryed to follow your instructions,but is hard without a visual aid. It could be easy if the parts are good. The rod does not goes all the way thru the vacum piston. So I may be good. I´m missing one small spring...

Can you send just send a picture of cross section of the carb, so I can at least know what I need to look for?
I have cutted a new gasket using the old one as a template.

Thanks a lot,

Ducatti

[John V Cliche]

Hi Ducatti,
I can't post pic's don't have a scanner either.
But I can E-Mail you pic's I only need your E-Mail address.
Regards
John

[ducatti]

Hi John,

Here is e-mail:

ducapira@yahoo.com.br

Thanks again,
Ducatti

[John V Cliche]

Hi Ducatti,
I just sent you several pic's from TM 9-1826C
Portrayal press www.portrayal.com
I hope they help
But I'm sure you will need to get a rebuild kit to get that carb to function properly.
Kits avail.at
www.dukw.freeserve.co.uk
vonrosenstiel@globalserve.net
There is a user logs on as" Lendlease " who might be able to help with a kit also he is in Austrailia.
I don't know of any suppliers closer to you.
Again I hope this helps
John

[ducatti]

John,

I really appreciate your help. Things are clear now.
I´m loading some pictures at address below, just in case you are interested. The progress is slow, but never stops...

http://www.surfacezero.com/g503/showgal ... ppuser=269

Thanks,

Ducatti

[John V Cliche]

Nice pic's Ducatti.
Where do you find your parts?

John

[ducatti]

I do have two sources of military surpplus in Sao Paulo, but they only have the heavy stuff, like gear, axles, u-joiunts, winches, some engine parts, but no more electrical, repais kits, carbs.

Most of my parts came with the truck when I bought it. It stayed parked for 30+ years in a particular museum, and it knd of complete, but is missing many details and cab interior parts.

Regards,
Ducatti

[thierryb]

Hi Ducatti,


I just had a look on your pictures. You’re doing a real great job on that truck and have started from a rough base. Is the colours of the engine + trans primer or final colour ?
The tank of my truck is out of order and starts to leak (full of rust – small holes at the bottom)… Was it easy to repair yours?


Thierry.

[ducatti]

Hi Thierry,

This is the final color. I saw a picture of one truck in sand and I liked it better than the OD.

Repair a fuel tank like I did is (very) timing consuming, and demand a lot of patient....cleaning (rust removers), cutting, making a new bottom, welding, clecking for leaking...find leaking...fix...more checking...fix again.
I want it to be like new, that´s why I have followed this path. Otherwise it is easyer to make a new tank, but it will not look like the original.
I have started the repair in two small areas of the bottom, and found out, when openned it, that it may develop new holes in the areas that initialy was ok...but too bad from inside.

Mine was really bad, and it may be easyer to fix your tank.

Here is the picture of desert sand truck I have found.

http://www.cvmarj.com.br/amplia/gmcs.htm

Regards,
Ducatti

[thierryb]

Hi Ducatti,

I just asked for the colour of the engine to know if early trucks may have had another colour as the common trucks…

I think my tank is as bad as yours. It starts leaking by a small hole right in the middle but as I removed the inside rust and cleaned it from the inside, I finally got 4-5 other small holes. So now I think I had 2 options :
1. Repair the tank as you did.
2. Use a resin 2 component tank coat that you can put in the tank, but I’m not sure if I can trust this process…
I’ve also noticed that the master cylinder on your truck is not the same as on other trucks. Is it original and typical for early trucks or do you think it has been replaced ? My truck was built May 11th 1941 and has the “normalâ€Â

[ducatti]

Hi Thierry,

The engines color when they left the GMC plant, per my investigation and information received, were gray. And found that my engine has a small untouched (original) area between engine and transmission with this color.
Most of the trucks have the engine painted OD, but as I´m painting the truck in sand, I find the gray better. Per my investigation, when a engine was replaced in during the war, the replacement engines comes in gray too.
Color specs: Batleship Grey - PPG-55-307

If your tank is ok from outside, then I would suggest you to try the resin first.

My truck has the early brake booster, this is the original brake for serial number below 41188 (as per TM 10-1501- June 1941). Your truck should have the same system at that time.

Regards,
Ducatti