Joined: Jun 09, 2011 Posts: 776 Location: Bellmore, NY
Posted: Mon Sep 19, 2011 7:19 am Post subject: Further developements on the M38A1 engine
The rebuilder called me today. He wanted to know if the engine had been revved over 3500. He says that does irreparable damage, and stretched the connecting rod bolts. He also wanted to know if I was taking over 55 MPH. I told him I had barely driven it, usually at around 30 miles a hour (especially with the old, shot, suspension system). It has revved a bit high, when trying to start it in the morning while it was still in my carport, as I have had difficulty and had to play with the choke and throttle cables, but no where else really. Any opinions on this?
Rod bolts also stretch naturally from tightening. Was there a bill of materials with the engine overhaul paperwork? If there are no new rod bolts on that list then assume the old were reused by the builder and the extra stretching came from his reusing the old bolts.The odds of you busting 3500 RPM with a rough running hard to start F134 are slim. Finding one of these engine with a tachometer would be one in a million so I really do not see where he came up with the 3500 RPM drop dead figure from to start with. Also any overspeed the engine may have had could have just as easily occurred with the previous owner.
I certainly hope that all the folks reading your threads are now understanding the need for a detailed inspection of a prospective jeep purchase by a qualified technician Before you hand over your money!!! _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Jun 09, 2011 Posts: 776 Location: Bellmore, NY
Posted: Mon Sep 19, 2011 8:30 am Post subject:
Yes, Wes, I have learned a valuable lesson, one I should have known when I had (not nearly as severe) problems with the CJ7 I bought 6 years ago. I looked for months for a "restored" M38A1, and couldn't find any close, so I got impatient, went of a slew of internet photos and false promises, and now I'm in a mess.
Joined: Jun 09, 2011 Posts: 776 Location: Bellmore, NY
Posted: Mon Sep 19, 2011 11:04 pm Post subject:
Wes, you can probably answer this best. I've been talking to alot of people, and several people who were in the military, and drove these jeeps, have said the things were tough as nails. The rebuilder was making it sound like a very fragile engine. That engine was used for almost twenty years, in M38A1s, CJ3's, 5's, and 6s, and Jeep trucks. I seriously doubt GI's in Vietnam when, they were dealing with the Viet Cong, were like "slow down, you have to baby the engine".
Don't confuse "Baby the engine in the field" with "Careful and delicate machine work".
The engine and the gear boxes when disassembled for overhaul require careful and often delicate handling and care. Close tolerances are often needed to be followed closely.
Once assembled and running in the field they are indeed nearly bullet proof.
Yes we drove them hard in the field.
What you are experiencing right now is a shop trying to defend it's product and they will often raise the bar for you to get over while lowering it for themselves. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Jun 09, 2011 Posts: 776 Location: Bellmore, NY
Posted: Tue Sep 20, 2011 12:59 pm Post subject:
So, in further talks with mechanics I know, they say that engine is probably bullet proof after it has been broken in and re-tuned. It is pretty sensitive the first 1,500 miles, and over revving it can guarantee the engine will never work right. The Speedometer never functioned, so I have no idea how many miles it had on it, but the seller says it was "brand new", as in a fresh rebuild. Although, just to reiterate, if it was over-revved, it was only like 5 times while trying to start it up, with the transmission in neutral, in my driveway.
I assume you are gauging the level of the overspeed by ear? As I mentioned above the tach equipped early jeep is very rare.
I have seen rods stretch in Hi Po racing motors at 8 to 9 thousand RPM but let's get realistic with this little 4 banger with all of 60 HP and rarely enough internal oomphh to overspeed itself.
The mechanics you are talking too are not L134 mechanics, _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
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