Posted: Tue Apr 05, 2011 2:18 pm Post subject: M38a1 Rear Main Seal
What is different about the Military F Head rear main seal from the Civillian version? Do they interchange? Is one better than the other? Where can I find a military version? Is there any other significant difference in the engine rebuild components?
Joined: Jun 25, 2008 Posts: 583 Location: Kern Co.
Posted: Tue Apr 05, 2011 3:15 pm Post subject:
Don't know the details but do your research before you start. I think I read one post a while back that said some aftermarket seals can destroy your engine!!!
Wes will probably know more about this. _________________ '53 M38A1 X2
This question is like which brake fluid is best or what paint OD is best. For the last 10 computer years I'v had to listen to the boastful ones spread their bull and the smart ones finally bow out and leave the field covered with the bull!
I'm going to offer the correct answer one time and then if the boastful ones want the field they can have it.
There is no military seal.
There are rope type seals and there are Garlock or lip type seals.
The rope came first. You can use the rope type in any 134 engine but the Garloc (Lip Type) can only be used in the later engines that tightened up the crank dimensional tolerance at the area the seal lip runs on or earlier engines that have had the lip sealing surface machined to the correct dimension for the lip type seal.
Willys and Kaiser offer this info in their early manuals where they say the lip type can be used in earlier engines but they omit the issue on the new crank dimension tolerances which are on their own factory blue prints. There has been a ton of lip on this topic and most has been in the correct area just some folks get lost in one area rather then examine and understand the big picture. This Tech Bulletin gives the needed dimension info.
If you follow this photo to my album you can view the rest of the Willys blue prints there as well.
One of the manufacturers of the lip type seal had a bad run of seals (Victor seal # 49650, WO # 800093) in the mid 90's and the failure of this run of seals has blossumed into an old wive's tale that puts all the troubles associated with the 134's rear main seal on that poor manufacturer's shoulders which is unfair and terribly confusing to honest folks that just want to know what is going on. It was this manufacturer who tried to defend itself by claiming the military engine cranks were different and could not use the their lip seal. No one has ever clarified which military 134 engine they were referring to. They actually should have advised against using their lip seal on any engine crank produced before 1951/52. Thus begins the wive's tale.
(Note: the 49650 is the Victor Part Number and the 800093 is the Willys Part Number. Victor put both on the seal because they were the OEM supplier of the seal to Willys) ( From the 90's on Victor supplied this seal to Felpro for their kits as well.)
So what do we do? Well there are just a few rules to follow.
1-Rope seal (which was used from 41 to 51) is the greatest and best and most reliable.
2-Stay away from the bad lip type seals (from the 90's) that are still being sold from NOS stocks. When installing any lip type seal if turning effort dramatically increases during installation or you notice a very bulging fit then get another seal.
3-If you do use a CURRENT PRODUCTION lip type seal make sure that your crank's lip sealing surface is within the tolerance limits. Just because you have a 1970 F134 does mean the crank isn't the early crank! The only way to be sure is to measure the crank.
That's it. Three simple rules without all the BS and Hype they toss around over on the G503 board.
So from 1941 thru 51 the rope seal was used and there were no problems.
Then in 1951 Willys introduced the lip type seal. during late 51 thru 53 several fit issues were resolved by Willys on their blue prints which included tightening the crank's seal journal dimensions and increasing the block and cap's seal groove dimensions.
Obviously from 53 thru the 70's most folks usually installed the correct type seal in their engine even though Willys manuals allowed the use of the late lip seal in the early engines. Then as these engines became more and more antiques they were machined more often and swapped around more often the year of the engine soon played a lesser role in determining which seals were used. The removal of asbestos from the original rope seal resulted in a bigger switch to the lip seal and by the late 80's early 90's this long term mix and match resulted in fit problems popping up for the lip type seal. The engine rebuilder's Assc addressed this way back then. Then the Willys/Kaiser/AMC OEM lip seal provider Victor goofed up several hundred thousand seals in 96/97. Depending on how bad the seal was that you purchased and how modern the crank's seal surface and block/caps seal groove were the result was better for the later parts and worse for the earlier parts that had not been updated to the 52/53 Willys blue print changes. The later issues were more publicized because by 97 we had the internet to relay the new rumors a million times faster than we could in the 70's and 80's. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Thanks for the info. So.... when I'm looking at parts list and a rear main seal is says that it's not for the military version, it just means that it MAY not work?
The ORD 9's do not show a military engine only seal and the Willys parts list do not as well so I assume you are referencing aftermarket seal company listings. An early military engine crank is no different than an early civvy engine crank just as a late military crank is no different than a late civvy crank. The key is the crank itself and what dimensions the seal bearing surface are at. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
The ORD 9's do not show a military engine only seal and the Willys parts list do not as well so I assume you are referencing aftermarket seal company listings. An early military engine crank is no different than an early civvy engine crank just as a late military crank is no different than a late civvy crank. The key is the crank itself and what dimensions the seal bearing surface are at.
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