I have seen many M151 series (IDA-4402) distributor lower housings used to rebuild M38 (IAU-XXX) distributors and I have many photos but it is quite obvious how the M38 distributors ended up with the M151 housings. It was because except for part number and subtle differences the housings would interchange and function just fine. A rebuilder can easily flood the market with several hundred units which if configured this way would lead one to believe that Auto-Lite made more different housings. The givaway here is the housing part number.
Now the carb comparison photos Gary posted a while back lack a little needed info. What is the casting number on each of the bowl sections? Is there a matching port for the extra bowl section port in the air horn and base sections. From my pile of YS637S's I found no matching ports in the upper and lower housings so the extra port in the middle section we are discussing serves no function on either version.
My YS637S bases did not use the port even when attached to a bowl section with the port.
For these reasons I feel that the odd port-less bowl section was either a subtle product improvement that deleted the unused port or a different model YS series carb bowl section was utilized in large numbers by a major rebuilder or even Carter herself.
Yes this is similar to a quess but I'd rather call it a theory based on the available facts. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Well, after abit of fooling around with these two different carbs this evening I have come up with the following:
Patent #'s on the extra vented carb center body ( the carb I think came first in production), are 1958614, 1258615, 2048535, 2208702, 2255296,and 2328604
The patent numbers on the later carb are: 0-548, 2048535,and 2328604.
As you can see the third and the last patent number on each carb is the same. What this all means is beyond me at this point.
Also, after some research I have come up with the following :
Each of the M38 manuals below picture the extra vented carb in them.
Ord 9 Sept 55 page 58
carb manual TM1826A 1952 page 107
powertrain and body TM 1804B 1952 page 34
engine and clutch TM 1804A 1951
TM 9-804 pages 95-96-109
TM 9-8012 january 1956 pages 113,152,
There may be more but thats enough for me. My point is, how can this body be a M151 body when the M151 wasn't even in production back when these manuals were first printed?
As far as I know every M38A1 had the smooth casting carb in production so my guess would be that the M38 smooth casting was the later production. This would negate the theory that M151 carb parts were used in M38 carb rebuilds as this carb body was already in production and pictured in the manuals well before the M151 was even thought of.
I wnet even further and tried to explore this vent more. I used a gun bore light and colored water to try to trace its path through the carb but found nothing. It was either plugged, blocked, or a blind hole.
This got me really bothered and I finally called a carb rebuilder who I have known for over 10 years or so and has rebulilt several carbs and made diaphrams for me in the past. He is well known in the military vehicle circles and has seen more carbs then most of us. JW gave me his expert opinion as he knew exactly what I was talking about with these two carb bodies. The extra casted vent is from the early production of M38's including the prototypes. The vent is indeed blind and no one he knows has an answer as to what carter carburator had in mind for this vent. Later production carbs were the smooth body ones similiar to the M38A1 carbs that appeared later on but with larger bores. He also never heard of M151 carb bodies being used on rebuilds for M38 carbs. He also had a interesting piece of information to add, and that is 90% of the carbs he rebuilds are of the early type.
So this is my theory, the vented carb is early production and the smooth casting the later one. Many more of the early castings apparently are in use and were produced, probably due to the limited production of the M38 and when the carb change came about, less were needed as the M38A1 was going into production to take the M38's place. This makes much more sense than M151 carb pieces being used, and the manuals, pictures, and expert opinions back this up.
Gary,
I see we agree completely now. I said several times in the past it was probably a subtle product improvement which warranted no change in bowl part number or carb model number. I also said several times in the past on this topic that there was only one model YS637S carb. Glad you see I was correct in these opinions I posted earlier.
As for M151 carb bodies I am really confused. You apparently did not read my earlier post slowly enough. I was drawing an analogy between Auto-Lite distributors where the M151 distributor housing was often substituted for the M38 housing since they are virtually identicle except for the data plates. This lead many people to believe that the M38 distributor came in both IAUXXX and IDAXXX series.
Bottom line is there are quite oftem subtle, non-performance related changes or improvements to many products that do not warrant a model or part number change and the issue on the carb bowls is just that. There is only one Carter model YS637S carb which had during it's production run metamorphised through a few esthetic changes. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
your right about the distributor quote. I missed that completely. I would still like to know what that vent casting was destined for. It must of had some reason for being in the initial design, and why was it taken out? Why wsa it casted as a blind port? Just seems strange to me for a run of such low numbers.
It may have been for the M37 carb. Remember a casting is usually machined to a certain spec number or drawing for a certain application. If part of the casting is not used in one model but it is used in another it may not be machined completely for the model that doesn't use it. You see the same thing every day in engine and head castings. IE the M38 800376 head casting is available with the boss for the front water bypass hose machined with pipe threads and also with the hole not drilled but the raised boss is still there. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Oct 06, 2006 Posts: 194 Location: Zephyrhills, Florida
Posted: Mon Jun 11, 2007 2:38 am Post subject:
I belive someone posted some photos on here at one time showing the differance. It's not really the carb itself thats the problem, it's the gasket that go's on the base throat. One will cover the cast channel as it suppose too and if you use the same gasket on the other it will only cover half of the channel, thus dump fuel into the manifold.
That gasket issue was explained a while ago and referred to the mixing of M38 (YS637S) Gaskets with M38A1 (YS950S) gaskets. Doesn't apply to this thread. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Aug 06, 2006 Posts: 44 Location: West Michigan
Posted: Wed Jun 13, 2007 5:01 pm Post subject:
Hello and sorry for the long delay in my response. I have yet to get her in to the mechanic because he is on vacation and was booked before that. I do have yet another question that I need to know if it could effect the way she runs concerning the carb. I called John today at Midwest Military but he is on vacation as well so I will throw it to you guys (Wesk) until I can call George Baxter tomorrow hopefully.
I just recently picked up the parts manual (ORD 9 SNL G-758) and if you look on page 70 the ventilating system Fig. 03-8 I noticed I am missing HH, AA, Z, BB, Y, G, V, CC and DD. I would find it hard to believe this would not effect it and now just wonder to what existent. Unfortunately for me after picking up this parts manual I am finding out that I am missing more than what I have as far as parts go. I won't even start with the wiring that is non existent. So #1 can I buy these missing tubes and #2 how much are they going to help and should I wait to get it in for fine tuning (carb) until I replace or add the tubes? As always thank you very much. You guys really are the best. _________________ I loved my Jeep!
As long as the hole for HH at the carb intake manifold area is plugged it shouldn't be an issue. Is your carb's bowl vent line connected to the intake tube? _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Aug 06, 2006 Posts: 44 Location: West Michigan
Posted: Thu Jun 14, 2007 6:13 am Post subject:
Line "E", Yes I do have that one hooked up. Also one thing I forgot yesterday, I had to buy an older fuel pump last year because of $$$ and it is the one with the glass bowl on top. At the bottom it has two (in/outs?) and I don't know what to hook up to them. I just put the EE line on the inside or closest to the block then put a plug on the outer one. How should it be hooked up? I am hoping to buy the one that is suppose to go on her later this year. Plus do you know if I can buy the vent tubing I am missing? Thanks again. _________________ I loved my Jeep!
Joined: Aug 06, 2006 Posts: 44 Location: West Michigan
Posted: Fri Jun 15, 2007 3:28 pm Post subject:
Thanks Wesk. Now do you mean this particular fuel pump sucks or something else? Also I think I found Hal on here for my tubing replacement. I sent him an email but am still waiting to hear back so I can order them. Thanks again Wes, I know I have a lot of questions and you still answer them as though it were my first. _________________ I loved my Jeep!
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