M38A1 by the book tune up

SteelTiger · Post by **SteelTiger** » Tue Nov 03, 2009 9:48 pm

I am tuning up an M38A1 using the manual and have a question about the use of the timing light. Will a standard light work on the spark plug wire itself of must I have an adapter to place over the plug (like the manual say.....)

Post by **wesk** » Tue Nov 03, 2009 10:09 pm

The plug lead is shielded with stainless steel braiding so the inductive style must have access to the inner wire. The adapter comes in the standard adapter tool set for military m series waterproof electrical systems. They seem to be overpriced nowadays at over $75 but still if you work on these systems then you should have the set. Yes you can spend many hours fabricating work arounds but then you must determine at how much per hour you value your time. By screwing the #1 shielded lead out of the cap you can replace it temporarily with a civvy plug wire and civvy plug and then you can use your inductive timing light.

miljeep52 · Post by **miljeep52** » Wed Nov 04, 2009 3:56 pm

Theres an adapter for sale on epay buy it now $25.00 free shipping seems like a good deal if you need one Item number: 220505251407
Scott out

SteelTiger · Post by **SteelTiger** » Thu Nov 05, 2009 8:18 pm

I ordered the part on ebay. Will see if it does the trick. Has anyone out there actually followed the 3 steps in the manual for a tune up (set points, adjust distributor, timing light (adjust distributor some more)). Were the results worth the effort or will I have to make more adustments and time by ear? Ideas?

Post by **wesk** » Fri Nov 06, 2009 11:02 am

I[ve been doing those basic three steps on point type distributors since 1960. It is the proper way and it is all that is needed.

Timing by ear is a rediculous exercise of intuition we really do not possess in our ear canals!

Ignition timing settings are established by the design engineer to be the best compromise between power, economy and longevity of parts. Timing by ear usually results in a very smooth running engine that may develope as much as one more HP but it causes heavier loading of the starter when cranking which shortens the life of the batteries and the starter. An aural errror in the retard direction can cause overheating of the engine.

So unless you're running a nitro dragster or 30" suspension rock climber or desert dueler just follow the manufacturers advice and set it by the book.

SteelTiger · Post by **SteelTiger** » Fri Nov 06, 2009 9:45 pm

I'll keep you posted then. I'll have to wait for the adapter to arrive, but plan on working on the first two steps this weekend if I have the time. I appreciate all the valuable info and like the forum a whole lot. I haven't worked on a jeep since I was a kid 35 years ago.

SteelTiger · Post by **SteelTiger** » Tue Nov 10, 2009 6:58 pm

OK - first two steps complete (though I could not seem to get the rotor off the cam - not sure why unless it is all one piece now, but that makes no sense.

I have ordered the adapter for the plug - am curious though, the manual shows the #1 plug on the engine to actually be the 2nd one back from the front - is that correct?

Post by **wesk** » Tue Nov 10, 2009 10:27 pm

If you are referring to the relative illustrations of Fig 75, 76 & 79 in TM 9-8014 then you are not aware that the numbering of the plug wires in the cap in fig. 79 are incorrect. Also #1 cylinder is at the very bottom of the illustration in fig 75 & 76.

The Army actually got it right in TM 9-8015-1 fig 106 on page 141.

SteelTiger · Post by **SteelTiger** » Wed Nov 11, 2009 7:25 pm

Wes, I am a bit slow on this and apparently don't have the right manual. When I am looking at the engine, which cylinder is the #1? Is it the first one from the front? My book makes it look like the 2nd one from the front to the back.

Bill

Post by **wesk** » Wed Nov 11, 2009 7:31 pm

SteelTiger · Post by **SteelTiger** » Wed Nov 11, 2009 7:58 pm

Great. That makes things easier. Surfing over to them now.......

BullRun · Post by **BullRun** » Wed Nov 25, 2009 9:56 pm

If you get lucky at a swap meet sometimes a Sun timing light for military jeeps will turn up. Adaptable to 6 volt, 12 volt, and 24 volt jeeps.

The adapter kits are over priced but if you have these two items tuning a military jeep is a snap.