M38 Spark Plugs

[Naugha]

Auto-Lite 2243 spark plugs (M38)

Does anyone still make these or have them in stock?
If found, would NOS 2243 plugs be reliable?
Is there an alternative to these plugs that fit the M38 ‘motorpool’ specs?
Are M38 plug ‘adaptors’ used much in ‘motorpool’ restorations.

What plugs are under the hood of >your< M38??

[wesk]

Does anyone still make these or have them in stock?

Yes. Just google 2243 autolite spark plug.

If found, would NOS 2243 plugs be reliable?

In a properly maintained and tuned M38 they do quite well.

Is there an alternative to these plugs that fit the M38 ‘motorpool’ specs?

The motorpool class are judged as they were found in use in the military during their service life. The military would not have used substitute plugs for the original shielded plugs.

Are M38 plug ‘adaptors’ used much in ‘motorpool’ restorations.

Based on my previous answer no.

What plugs are under the hood of >your< M38??

2243

[Naugha]

Thanks Wes.

I had been searching for Autolite 2243 and getting lots of hits where they were no longer available.

While searching for other plugs on the chart I hit on “Military Spark Plug 2243 M series“ ...... which is how Midwest Millitary lists the Autolte plugs on ebay, at least the pic looks like an Autolite and says 2243. I had looked earlier on the MWM web page and did not see the 2243 plugs. I am good at ‘not seeing’.

BTW.
Next on my list of ‘can’t find/ high dollar’ items is a M38 YS carb or good core. I know where big money will buy one with a year warranty but the $600 price tag makes my WO carb look tempting ...... still got a long way to go so I will think more on this another day.

[RonD2]

Spark plugs wear out and need to be replaced once in a while, they're "consumable". Because those special M38 waterproof plugs aren't made anymore, and the few folks who saw it coming and stockpiled them now want north of $25 each for them, I think I'd seriously consider going with the adapters at $25 each one time buy and use common spark plugs that can still be had for about $3 each.

I might maybe buy one set of 2243's, but keep them in a glass case just for show and tell.

If I remember correctly, I recall hearing that one of our venerable MV parts vendors looked into having a run of 5,000 2243's made but it was cost prohibitive.

My M38 converted to 12v CJ distributor and coil so I'm kinda glad I don't have to make that decision.

[Naugha]

I might maybe buy one set of 2243's, but keep them in a glass case just for show and tell.

I like the way you think..... always have a Plan B. Maybe make a display of “stuff that you would find on a Factoty Resto for an extra 10k and two more years of work that stays on a trailer in the garage.”

I briefly thought about an ‘original’ restoration but later realized that would be unrealistic for what I really wanted to do with the jeep ..... which is to drive around the town square with the wife on a beautiful day and wave to smiling folks who may not know how much effort it takes have such a toy but do appreciate the final product.

[Naugha]

It's amazing.
Just push the button.
No pounding or cussing needed.

[RonD2]

Curious, not 2243's ?

[wesk]

2327 Autolite Different reach 7/16" vs 3/8" for 2243. Not meant for L134 or F134.

[cobra5]

Not sure if this is a viable option for you but if your jeep came with an original set of waterproof sparkplugs, just clean up the electrode portion, install and drive your jeep to make sure the plugs are good. If all good, remove them, clean upper portion, repaint them using high temp black paint and then don't reinstall them until the jeep is entered in a competition. In the meantime, buy a set of sparkplug adapters and civilian plugs for everyday driving.

[Naugha]

Guys, this is the stuff that drives me to drink ..... well, I don’t always need a reason but this will do it.

The ad for these plugs reads:
“Military Spark Plug 2243” and the M38 is listed as appropriate for the plugs.

The supplier is even one of RonD’s top recommended sources.

I suppose the fellow will make this right (he has a good rep), but before I ask for a refund or different plugs, let me double check a few things.

** Is there any stretch of spark plug interpretation/identification that would make the plugs I bought conform to the name “Military Spark Plug 2243”.

Does “2243” stand for several plugs that may or may not be correct for my M38 or does “2243” pretty much identify ONE type of plug and this ain’t it?

Thanks for the info
Don

[RonD2]

Don,
2243 is a unique part number used by one manufacturer, in this case, Autolite. Several manufacturers can and did make the exact same spark plug, but each will use his own unique part number. Wes provided a handy cross-reference chart that shows this. It's nothing new, the same thing applies to most auto parts on the planet. Many makers of the same exact part using many different part numbers. And to add to the confusion, sometimes a maker will change his part numbering scheme in mid-stream.

2243 is a "new" Autolite part number. So is 2327. But ARL8S-A is an "old" Autolite part number for 2327.

You have to look carefully at the cross reference of part numbers to see if the various part numbers are identical and interchangeable. Sometimes a part number difference is just a heat-range for a hotter or colder plug that can be used for different circumstances. On the other hand, many times a different part number clearly isn't interchangeable.

When I zoom in on the package of your new plugs I get a Federal Stock Number (FSN) of 2920-569-8964 and a part number of ARL8S-A. Am I seeing that correctly? During the early 1970s, the government added 2 digits to the FSN making it a NSN (National Stock Number), in this case your FSN becomes 2920-00-569-8964, and you can google that number and get a list of many different part numbers made by many different makers, all catalogued under that stock number (yes, all equally interchangeable).

But in this case, the "reach" between the 2243 at 3/8-inch and the plug you bought is different, the ARL8S-A is slightly longer at 7/16-inch. Reach being the distance the plug protrudes into the combustion chamber. It's important. Too long and worst case bad things can happen like valves or pistons slapping the plug into pulp. Best case is your motor doesn't run as sweet as it could.

I don't know if the extra 1/16-inch is a mechanical show-stopper or not, but the charts Wes provided clearly say it's not interchangeable on the M38. The ARL8S plug is clearly not correct for the M38. Doesn't belong in your display case.

Nothing wrong with naming the vendor. People make mistakes sometimes. And sometimes they don't and we all learn something. Get it out in the open.

I thought it was a little premature for the "no cussing or pounding needed" when I looked up your part number.

Not enough space here to get into the military's mil-spec part numbering scheme, but it matters. The MS number for the 2243 and your plug aren't the same. Close, but not the same. Maybe more on this later.

[RonD2]

Page 149 of the M38 ORD9 lists 4 part numbers for the spark plug:

AC-5569357 (AC Spark Plug Division of General Motors)
WO-801791 (Willys-Overland)
WO-801656 (Willys-Overland)
AL-AR5S (Autolite)

To answer your original question "What plugs are under the hood of >your< M38 ?"

I'm using Autolite 295's. Got a box of 10 NOS delivered for $3.25 each.

[Naugha]

When I zoom in on the package of your new plugs I get a Federal Stock Number (FSN) of 2920-569-8964 and a part number of ARL8S-A. Am I seeing that correctly? RonD

Yes.
I will contact the supplier and see what’s up.
Thanks for catching an issue that is beyond my knowledge set.

Don

[RonD2]

Don,
Here's a link to the NSN look-up for 18 different part numbers catalogued under that now obsolete NSN: https://www.nsndepot.com/NSN/2920-00-569-8964

Curiously, ARL8S-A isn't one of them, but ARL6S is. Neither one is an M38 plug.

Not exactly pertinent, but mis-labeled government packaging wouldn't be the first time that parts like that were seen on the open market years later. It sure beats getting a correctly labeled but defective (rejected) government part that our government sold to the open market anyway (and then installing it). Sometimes our Uncle Sam can be an idiot that way.

Which raises the question: is there a part number stamped on the body of your plugs?

Good luck!

Btw, If you take up drinking, I discovered that an ice cold, but hard cider can go down pretty good in this hobby right about now. Slightly bitter green apples are the best.

[Naugha]

Using a loop, I see:

Autolite
MS35911-2
Resistor (In a script type font)


Also, I found a plug listing from another supplier (which may be wrong) that includes the MS35911-2 seen on the plugs I bought.

Autolite # BR4S, Champion # XED14, National Stk. #: 2920-805-2646, Mil. Spec #: MS35911-2.