working on my M38A1 again

tommy · Member Joined: Jan 03, 2010 Posts: 54

After several months of letting it rest , I am working on my 1955 M38A1 again. I have the front sheet metal off. The cylinder head is off and the bellhousing to engine bolts are out. Everything else is disconnected in preparing to remove the engine. I hope to "unstick" the engine and clean and detail it. I found that the right side motor mount was broken and will be replaced. Thanks.

53a1 · Member Joined: Jun 25, 2008 Posts: 583 Location: Kern Co.

Since you are starting with the engine I would keep the rest of the vehicle intact until you have a running engine.

I found once you start tearing the chassis down you use up a lot more space in the workshop. The engine can also be a major expense road block and halt the project.

tommy · Member Joined: Jan 03, 2010 Posts: 54

Thank you for the tip. I plan to do whatever it takes to get the engine running before any other major repairs. I believe that being able to start it and hear the engine run occasionally will motivate me to tackle some of the less enjoyable tasks necessary to drive the Jeep.At present I am hindered slightly by vertigo that I a suffer from occasionally. It makes lying down or even working bent over very unpleasant at times. We all have our own bear to cross Laughing

I suppose.Thanks again.

tommy · Member Joined: Jan 03, 2010 Posts: 54

The engine is out. I have the oil pan off and #1 and #2 rod caps off. The lower bearing halves look like new, as does the crankshaft. I figure with the rod caps off , I can attempt to remove each piston, one at a time. The pistons are all in mid-travel, or half way up (or down) in the cylinders. I was a little shocked when I first removed the head to see all the pistons lined up that way. I hope to remove #3 and #4 tomorrow. If all goes well and I am able to remove and replace the pistons and rods I intend to reuse the rod bearings and will probably not remove any main bearing caps. Cool

tommy · Member Joined: Jan 03, 2010 Posts: 54

#3 and #4 rod caps are off now. Both bearings also look like new. I'm starting to believe that the engine was rebuilt just a few miles ago, as I was told by a previous owner. There was NO ridge in the tops of the cylinders and the engine is very clean inside. The clutch is like new also. If I can unstick it maybe it will run well.Thanks

tommy · Member Joined: Jan 03, 2010 Posts: 54

My plan to remove the pistons with the crank still in the block didn't work. The crank is now out and the main bearings look perfect. Though this is the first Willys 4 cylinder engine I have ever disassembled , I have worked on several other engines over the past forty years. This engine is the first I have ever seen where all the wrist pins are seized in the pistons. They are so tight that I was only able to move them by using a pry bar between the rod end and the block. No rust can be seen in the cylinders or on the pins.I sprayed the pistons and pins with PB Blaster and will try to free them up while they are still in the block as I have no vise to clamp them in when they are out. After I get the pins freed up I will try to drive the pistons out from the top with a block of wood. Confused

wesk · Posted: Tue Jun 15, 2010 11:17 am Post subject:

The seized wrist pins shouldn't have any affect on driving the pistons out the top of the block. If you can't get the rod to hang vertical just loosen the rod's small end pinch bolt. They do not come out the bottom!

Do you have a F134 overhaul manual either military or civilian? If not download the free PDF copy on our downloads page and it will walk you easily through the entire process.

Are your main bearing caps number or match mark stamped?
_________________
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

tkjeeper · Member Joined: May 24, 2010 Posts: 17

Plan on doing this myself, keep us posted on your progress. Good luck.

tommy · Member Joined: Jan 03, 2010 Posts: 54

You're right . I know that as long as the big end of the rod will pass the block the rod and piston would normally push out thru the top. My thinking was that if I have to use a block of wood and hammer to remove them, the top of a piston is a more solid surface to hammer on than the other end.The cylinders should not be tapered enough to cause the pistons to be tighter in the bottom than the top , right? My rod caps are numbered , but the mains are not. I don't see how I could mix them up though, knowing that the thrust bearing is part of the front main bearing , # 2 is similar, without the thrust , and the rear cap is completely different. I still plan to spray the pins and try to "loosen" them up before I actually remove the pistons from the cylinders. Although I didn't intend to get as involved as I already am, I suppose now I will be removing the pins from the pistons to free them up. I would worry about the pins seizing again if I don't.Any advice is appreciated. Thank You.

wesk · Posted: Tue Jun 15, 2010 6:59 pm Post subject:

The piston skirts will not clear the bottom of the block. Taper is not the issue.

Just spray a good penetrant on the wrist pins and work the rod side to side and they should free up.

All you do is plant the end of a 18" long 2x4 against the inside curve of the rod bearing upper surface and hammer the piston/rod assembly out the top.

The #1 and #2 main caps are identical. They fit either spot and can be reversed 180 degrees side ways. So once you mix them up you'll need to have a machine shop do an alignment check or risk binding main bearings when you go back together. Those caps were align bored when new as installed on the block. Same goes for the flywheel which can be installed 180 out and foul up balance and timing marks.

Match marking machined parts is the cornerstone of keeping machine costs down on engine building. Do you not have a manual?
_________________
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

tommy · Member Joined: Jan 03, 2010 Posts: 54

Thanks again. You know more about these things than I do , by far. I have the engine back upright and the cylinders soaking now. I will mark the main caps tomorrow. The flywheel might be a problem though as I have already removed it without marking it . How can I check it to keep from installing it 180 degrees out? Sorry , I have no manual , and have never been able to download the one on here.

wesk · Posted: Tue Jun 15, 2010 11:05 pm Post subject:

Do you not have the adobe reader installed on your computer? At least try to get some close by assistance with the download and get the manual on your work bench. Perhaps a member close to Tommy can download and place a copy on a CD for him.

The cost in both labor and parts can easily double or tripple by guessing first and finding out later it was the wrong thing to do. Not only can things get expensive but in many cases the disappointment causes folks to abandon their projects early on.

Does your flywheel have two tapered shank dowel bolts or two straight shouldered dowel bolts? Are there timing marks on the front face of your flywheel?

If it does have the timing marks then get #1 piston TDC on compression (ready to fire) and the flywheel mounts with the timing marks on the starter side.
_________________
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

tommy · Member Joined: Jan 03, 2010 Posts: 54

I have the two tapered studs. I searched on here and found what timing marks would look like if my flywheel had marks. There are none on it.However, I can tell which way the flywheel came off by the "print" of the crank in the flywheel. I have punch marked the flywheel and crank in case the print gets cleaned off during reassembly. I will try again tomorrow to remove the pistons from the block.

wesk · Posted: Wed Jun 16, 2010 10:58 pm Post subject:

Very early F134's had a hole in the bell adapter plate next to the starter and the timing marks were seen thru it. None of the A1 engines would normally have that hole. They all had timing marks on the front timing cover and lower crank pulley. If your flywheel has none then you'll just have to flip a coin to reinstall it. The engine must be a very early A1 engine since it has the tapered dowel bolts. What's the serial number above the water pump and the casting number on the lower right side?
_________________
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

tommy · Member Joined: Jan 03, 2010 Posts: 54

I can reinstall the flywheel like it was when I removed it. I suppose it was reinstalled correctly when the engine was rebuilt before I got it. At present I am unable to see the numbers above the waterpump. The numbers on the right side are SD 807895 15. The original color on my engine appears to have been blue. Would that be correct? Thanks


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