M38-YS637S Carb question

DFoley · Posted: Fri Jun 14, 2024 8:04 pm Post subject: M38-YS637S Carb question

The M38 YS637S carb has a small plug (freeze plug?) on the fuel bowl. On my Carb this plug has popped out (I don't have the plug). What is the size of this plug? Is it a "standard" size which can be purchased at a parts store (ie. NAPA)? Is this something easily fixed myself or does it need to be pressed fit with special tools that would be best completed by sending the carb to a rebuilder?

Link to a pic: https://drive.google.com/file/d/1zwKcHx-y0TTBw-mMi28fsRnCzft9Pe0m/view?usp=sharing
_________________
Dan
1951 M38

wesk · Posted: Sat Jun 15, 2024 1:18 am Post subject:

Dan,

You are in an unusual situation. That appears to be a good ole fashion Welsh Plug or as you called it a freeze plug. I have the detailed layout of that carb in My TM 9-1826A where there is no mention of this welsh plug and it is not in any of the parts illustrations. I checked my M38 ORD 9 and same thing. I don't have a YS637S handy right now to measure the diameter of the welsh plug.

You should check the diameter with a ruler and see if you can find one at the auto parts store. They are very simple to install. You just tap it into the hole and then smack it dead center with a small punch to make it tight.
_________________
Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php

RonD2 · Posted: Sat Jun 15, 2024 3:45 pm Post subject:

Hi Dan,
I took a tight photo of mine (shows a trademark) but for some reason the site won't let me upload it to show.

If it helps, I measured it at 11/32nds (.34375) with a steel machinists ruler and my calibrated eyeball.

A quick interweb search turned up a couple of possible sources here:
https://www.carburetor-parts.com/expansion-plug-85-256
https://www.hubbardspring.com/product/expansion-plugs-aluminum/

Here's a short video shows how to replace one.
Welch plug starts at the 1:40 mark: https://www.youtube.com/watch?v=6NvIffPLf0A&t=238s

Good luck!
_________________
Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51

“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari

wesk · Posted: Sat Jun 15, 2024 4:44 pm Post subject:

Ron,
Did you see any identifying numbers on the plug?

The management had to reduce photo loads on the web site.
_________________
Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php

RonD2 · Posted: Sat Jun 15, 2024 5:29 pm Post subject:

Wes,
No numbers (or I would've given them).
Just a logo. Looks like a stylized "H".

Might maybe an earlier version of the Hubbard logo (seen in the link I provided above)?
They've been in business since 1905.

Is the prohibition on more photos permanent?
Could I delete photos from my album to get space for new photos?

Photos are worth a thousand words.
Good photos are worth even more.
_________________
Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51

“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari

wesk · Posted: Sat Jun 15, 2024 11:31 pm Post subject:

Ryan Miller and Jake are working on the high band usage to keep the web site cost down and avoid the frequent web site drop offs. Best to direct site management issues directly to them.
_________________
Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php

RonD2 · Posted: Mon Jun 17, 2024 10:57 am Post subject:

_________________
Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51

“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari

DFoley · Posted: Mon Jun 17, 2024 12:19 pm Post subject:

Thanks Ron,
I had measured the opening as 9mm=.35433

No parts store in my small town has anything close to this size in stock.

I've ordered two plug sizes:

Hopefully one of these will suffice.
_________________
Dan
1951 M38

RonD2 · Posted: Mon Jun 17, 2024 12:27 pm Post subject:

Glad to help.
Let us know how it goes Dan.
Might want to consider using a little smear of gasket sealant on it?

Curious ---> what's behind the plug in the hole?
Is it blind (closed off) or is it actually open to the float chamber?

I'm struggling to understand why they'd put a "clean out" hole for the float chamber there when the bowl would typically get cleaned during a rebuild.
Can't really see a mechanic messing with removing the plug without also taking the carb apart to clean everything else?

Was thinking if it's a blind hole maybe it's only for a jig fixture in the casting or machining process?
_________________
Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51

“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari

DFoley · Posted: Mon Jun 17, 2024 12:55 pm Post subject:

Oh no...it's open! I can clearly see (and touch with a probe) the float in the bowl chamber. In fact it was the copious gas spilling from this hole that initially got my attention.

Curious, as Wes previously mentioned, there is no information about this plug in any reference material, but it is clearly present on mine and every picture of a Carter YS-637 I've ever seen.

I even reviewed the parts list from several carb rebuild kits for this carb and none mentioned or included a replacement plug.
_________________
Dan
1951 M38

wesk · Posted: Mon Jun 17, 2024 8:36 pm Post subject:

Well folks I found an old Carter spec sheet with a parts list and it includes the two expansion plugs with an illustration.

Here's the IPL illustratioon where the large bowel expansion plug is NOT illustrated.

_________________
Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php

DFoley · Posted: Wed Jun 26, 2024 7:14 pm Post subject:

Expansion (welch) plug installed. All seems OK now.

I can report 11/32" plugs were a skosh too small. The 23/64" plugs just snugly fit in the hole and when dimpled with a punch fit nice and tight.

FYI...Plugs were purchased from Quadrajetparts.com, set of 5 plugs $4

Thanks for y'alls advise.
_________________
Dan
1951 M38


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