My M715 'rework' project

[M813rc]

Back in November when I went to look at my Mighty Mite, I also ended up buying an M715 from the same chap.

It is a significantly modified truck, and had a known bad 350 V8 in it. That said, it also looked a lot like one I had seen pictures of and admired for many years (picture 1 attached), so I agreed to give it a new home.
This will surprise some who look upon me as something of a purist, as I prefer military vehicles in their stock service guise, rather than modified (except perhaps for safety features), but I'll admit I've had shocking ideas lurking in my head for years on what an ideal M715 could be.

The Marines kept the M715 in service in limited numbers well into the 1980s, so I saw quite a few of them. These sported 11.00-16 tires rather than the stock 9.00-16s, mostly because the 11.00s gave better performance in beach sand, which Marines tend to transit rather regularly. I liked the way they looked.

Having seen the M715s/M725 that Barrman and Sermis had modified with 6.2 diesel engines, I was duly impressed, as I have long been suspicious of the stock Tornado engine. Barrman said the 6.2 was pretty much an ideal engine for these trucks. I also think that most vehicles could benefit from being diesel powered. Since the Tornado from this M715 was already gone, and the 350 was almost assuredly toast, a 6.2 was a logical choice to stick in there, and I just happened to have one sitting around waiting for a home.

So.... how do I justify in my little brain the significant modification of a military vehicle?
The answer is to indulge in a little "Whifery" (What If...).
What if the M715-series had not been cancelled early and gone the full anticipated production run of something like 70-80.000, and what if it had then served (as it should have) into the 1990s alongside the Humvee? Would it not make sense that it would have had upgrades along the way? And would it not make sense that upgrades could include sharing common items with the Humvee/CUCV vehicles?
Since the military did away with all gasoline powered tactical vehicles during that time, surviving M715s would have had to get a diesel of some sort anyway, makes sense they'd use the common 6.2.
That would all make the concept of an M715 with 6.2 engine and Humvee tires quite logical and feasible. Since this is Whifery anyway, I will presume that there was a less modified M715A1 in there somewhere *, and I'll call mine an M715A2.

So, along we go with this rework. There will be some modifications of the M715 from 'as bought' as shown below to remove some of the unwanted civilian embuggerations.
If anyone is an actual purist, please look away now lest you be mightily offended!

Cheers

* PS - I had a little thought niggling in my mind for a while reference the M715A1 designation and why I didn't want to use it, and finally remembered that designation was used for a Kaiser Jeep proposal, that was not accepted, for production series modification. This included changes to the engine, and larger tires (10.00x16) for better clearance and off road mobility. I have a PDF copy of that proposal in my files.

Pictures -
1 the truck that led me to impure thoughts about M715s
2 and 3 are the one I bought, complete with troop seats and tools
4 and 5 are the Gladiator trucks the M715 was based on, which also explain where those pie pans in my front panel came from.

 

[NDT]

I had no idea USMC used M715s AT ALL! Do you have pics?

 

[flyfishtrailer]

I like your thought process on this one and agree that it would have used a diesel engine if production had continued. I will be watching the progress on this one!

 

[M813rc]

I had no idea USMC used M715s AT ALL! Do you have pics?

The Marines used all the types in the M715 series. M725s were used as ambulances and as radio trucks (without the red crosses, of course!). I saw them all on Camp Pendleton c.1979-1981, and in Norway in 1980.
The Seabees were still using a few M726s then too, and I saw one M715 used by USN Beach Masters.
One of my own M715s has faint USMC markings visible on it, as well as painted out USN markings on the tailgate. Unfortunately, the data plate is not the one that should be on the truck! I grew suspicious because the plate says W/W and my truck obviously doesn't have one. I looked at the VIN on the frame, it doesn't match the data plate. Or the title... (which does match the data plate)

Pictures of USMC M715s are like hens teeth, it seems. I took some in Norway in 1980, but they are in an album, in a box, which is ??? after I moved house. Most of the ones on the interwebs are of restored vehicles.
If anyone has in-service pictures of M715s in Marine markings, please feel free -nay, encouraged! - to add them to this thread.

I also took some pictures at Jack's yard outside Tucson a few years ago to document the markings (I collect as much information about Marine vehicle markings as I can).
There were numerous USMC M715s there (Jack seems to have a LOT of old USMC vehicles), but most were pretty picked over. My notes say that the hood on the bed of the M715 with the white hood is the one that actually belongs to it, the data plate said USMC and had the same serial number. The other hood doesn't look like it belongs to the truck it's sitting on, I don't recall if I checked that data plate.
In the b/w photo, you can see the nose of one, and the back of another M715 between the A-4s. The visible hood has Marine markings, the tailgate of the other looks like it does too, from what little of it that can be seen. Picture taken in Japan in the early 1970s, most likely at Iwakuni.

Cheers

 

[M813rc]

As anyone who looked at my Mighty Mite work thread now knows, in the wee hours when indoors because it is too dark to go play with real trucks, I often create photo notes to help me decide on, and keep track of, desired changes. I also do this in case I suddenly vapour lock, then perhaps my kids could use them as a guide and complete the truck the way I wanted it done.
Anyway, they give a good idea of where I plan to go with this project, so they are attached below.

The story on the bad 350 engine is as follows -
Someone had the bright idea that the M715 could somehow benefit from louvres in the hood, so they cut holes in said hood and installed two louvred panels.
(Yes, spellcheck, I KNOW Americans spell it "louver", but I didn't learn to spell here, which is why I also write vapour and colour and honour and ....)

Whatever purpose these panels were supposed to serve, they had one unintended consequence.
The M715 sat outside in a Houston frog-strangler rainstorm one day, and at the time had nought but a paper air filter over the carb, which happened to be directly below the louvres.
You've guessed it - torrents of rain poured in the louvres, straight through the filter into the carb, and filled the engine with water!
Afterwards, the then-owner dragged it inside and removed the spark plugs and water poured out the holes. Unfortunately nothing else was done to save the engine, so it just sat without plugs for several years. This sordid tale was all revealed to me prior to sale, and the truck was priced accordingly, so...

Cheers

 

[Mullaney]

As anyone who looked at my Mighty Mite work thread now knows, in the wee hours when indoors because it is too dark to go play with real trucks, I often create photo notes to help me decide on, and keep track of, desired changes. I also do this in case I suddenly vapour lock, then perhaps my kids could use them as a guide and complete the truck the way I wanted it done.
Anyway, they give a good idea of where I plan to go with this project, so they are attached below.

The story on the bad 350 engine is as follows -
Someone had the bright idea that the M715 could somehow benefit from louvres in the hood, so they cut holes in said hood and installed two louvred panels.
(Yes, spellcheck, I KNOW Americans spell it "louver", but I didn't learn to spell here, which is why I also write vapour and colour and honour and ....)

Whatever purpose these panels were supposed to serve, they had one unintended consequence.
The M715 sat outside in a Houston frog-strangler rainstorm one day, and at the time had nought but a paper air filter over the carb, which happened to be directly below the louvres.
You've guessed it - torrents of rain poured in the louvres, straight through the filter into the carb, and filled the engine with water!
Afterwards, the then-owner dragged it inside and removed the spark plugs and water poured out the holes. Unfortunately nothing else was done to save the engine, so it just sat without plugs for several years. This sordid tale was all revealed to me prior to sale, and the truck was priced accordingly, so...

Cheers

View attachment 899216 View attachment 899217 View attachment 899219 View attachment 899220

.
Ha!

I love old George's commentary about removing the "U" in a bunch of words.

Real similar to . . . (see below)

 

[NDT]

Will you try to fix that hood? I recall finding a decent hood was a challenge 20 years ago.

 

[M813rc]

Will you try to fix that hood? I recall finding a decent hood was a challenge 20 years ago.

Since you asked....

I've actually worked on this project a little here and there since December. Nowhere near the splendidly meteoric performance of Kendelrio with Gertrude!

I entertained several options for the hood, including complete replacement or trying to weld patches in. But I realized finding a better hood would be difficult at best and spendy. Welded patches would likely never be invisible (not with my skills!). I also really wanted to keep the original hood if possible, so finally settled on the simplest and most sensible answer - this vehicle is a utilitarian design, why not a utilitarian looking fix?
Which meant to just replicate the panels, but in flat plate without the louvres.

I drilled the rivets out (all 82 of them) that held the two louvred panels on. Amber is a whiz at the plasma table, she cut out two replacements the exact size of the removed panels. I then used the louvred ones as templates, clamped to the flat panels, to drill 41 holes apiece in them.

Everything was cleaned up and given two coats of primer. To be sure of a leakproof joining, I used liquid gasket material between the hood and the new panels, and riveted them on. My main concern was whether or not the new panels would flex, or allow the hood to flex, as they did not have louvres to add stiffness, and the hood metal was a bit wobbly with the big empty holes in it. But that was a needless worry, the panels and the hood proved to be very stiff once riveted together.
Any gasket material that oozed out was cleaned off and the panels were given a final coat of primer.

I'm rather pleased with the results. I figure that most folk won't pay much attention to the repairs, assuming they have a purpose or were supposed to be there. And in reality, the only person who need be satisfied with the repair is me, and I am.

Cheers

1- the unfathomable louvres
2- removed!
3- old and new. The brown is not rust, it is the residue from deteriorating plastic coating stuck on the metal. Solvent took it away nicely.
4- My coon-trap painting stand displays it's usefulness yet again
5- hood primered up
6- gasket material
7 and 8- all riveted on and then primered

 

[M813rc]

The topic of the hood brings us to the splendid buffalo hood ornament, which while very cool, absolutely does not belong on an M715!
A little web research revealed that is is from a 1947 Kaiser-Frazer automobile.

It was therefore removed, which left four residual bolt holes. Again, rather than try to weld them up and get them smooth, I went the utilitarian route and put four studs in the holes with lock nuts on the inside. The holes got a squib of gasket material just to seal them up and hopefully deter any future corrosion there.

While I was at it, I also unbolted the hood footman loop, put sealer in the holes and remounted it. Barrman has had problems in the past with rain water leaking in those bolt holes and dripping onto his air filter housing. Better safe than sorry.

I thought the buffalo might look good on Jason's former State Trooper Charger. I got a chuckle but also a firm "No!!" from him.
So the buffalo now keeps an eye on my home office from the top of a bookshelf.

Cheers

 

[NDT]

What are your plans for the transmission? The wet 350 might have the Novak adapter to couple a GM bellhousing to the T98. The 350 can handle 3200 rpm at 60 mph but the 6.2 not so much. So the T98 might have to go.

 

[67Beast]

Looking like a great project. As for the hood, a hood from any the FSJ Jeep's (J-truck, Cherokee, and Wagoneers) will fit. You just need to add the holes for the hood tie downs and blackout light brackets. And depending on the year you may have to remove the front cross bar from the civilian hood. And as a purist, I don't mind when people mod out trucks that were already cut up. It gets cringe worthy when someone takes a pristine truck and cuts it up to make some mud truck or something like that. And I looked through my archive of M715 pics for USMC pics and didn't find many either so it's good to see if anyone else has some.

 

[M813rc]

What are your plans for the transmission? The wet 350 might have the Novak adapter to couple a GM bellhousing to the T98. The 350 can handle 3200 rpm at 60 mph but the 6.2 not so much. So the T98 might have to go.

For the moment, the plan is to see how it works out with as few changes from original M715 as possible. The 6.2 mates nicely with the adapter bellhousing from the 350. We'll just have to see how driveable it is and go from there. That said, this will be a parade and show toy, not regular transportation, so I won't ever be in a big hurry to get somewhere, a lower top end is not a worrisome prospect.
I did toy with the idea of using the 700R4 transmission that came with the 6.2 (out of a 1991 Suburban), but that would require surgery to crossmembers and such. It is an option for the future, though, if my left leg becomes increasingly uncooperative as antiquity takes a further hold on me. I damaged that leg in a helicopter crash many moons ago, then got hit by a car about 25 years ago, so a clutch is less of a friend to me these days than it used to be.

Cheers

 

[M813rc]

And as a purist, I don't mind when people mod out trucks that were already cut up. It gets cringe worthy when someone takes a pristine truck and cuts it up to make some mud truck or something like that. And I looked through my archive of M715 pics for USMC pics and didn't find many either so it's good to see if anyone else has some.

Thanks. Happily, on this truck I will be reversing quite a bit of civilian modification and taking it back toward stock military, just not all the way. Should a future caretaker wish to return it to stock, it should mostly be a matter of sourcing the appropriate parts and bolting them on.
I too cringe at some of the abominations I have seen wreaked upon military vehicles (or antique civilian ones) and can get positively vocal on the subject of chopping up trailers like M416s to make offroad trailers. By the time they are finished, the abominators could and should have started fresh with a civilian trailer, but have instead ruined an historic vehicle and removed it from the pool of those available to collectors who would cherish it.

(Allright Rory, easy now lad. Shhhh...there's a good boy........step away from the soapbox...that's it..come on...)

I'd be very interested in seeing any USMC M715 series truck pictures you have!

Cheers

 

[Barrman]

2500 rpm at the drive shaft is about all most NP200 transfer cases can stand without overheating. 4th gear in the T98 is 1:1 so 2500 engine rpm will get you 48 mph with stock 9.00-16 tires. The 11.00-16 Michelin’s make 2500 rpm 52 mph.

Basically, you will get the same road speed as the bigger 10 tire siblings you have. Even though the 6.2 will turn more than 2500. It sure does sound happy and healthy at 2500. Even though I have a NV4500 in my 6.2 powered M715. I am transfer case limited to the same road speed.

 

[M813rc]

Thanks, Tim. I always value your input.

When I told buddy Scott, aka Reloader64, that I had bought these vehicles in Houston, his first response was "When are we going to pick them up?"
He also announced that he would much rather make the trip in air conditioned comfort at highway speed, so we would be taking his dually instead of Lola, my M1028A2. When I pointed out that Lola is air conditioned, he asked if I had missed the "comfort" and "highway speed" parts of his statement.
The man does have impeccable logic.
So, off we went and hauled the M715 home. Jim, the chap I bought the vehicles from, had already taken that unwanted headache rack off of the truck, and had replaced it with a custom set of steel tube bows he had. He wanted to keep the Humvee tires for his other M715, which wasn't a problem for me as they were a bit old and I had a set at home with much newer dates on them. The tires and wheels in the picture are just rollers, they look pretty good till you get up close and see that the tread is literally coming apart.

The keen eyed may notice that in the "about to head home" picture, the front bow on the M715 is vertical, and in later pictures it is leaned back about 15*. We won't get into how Scott figured out the M715 on a trailer was about 2" taller than the cross beam on his carport at home, but suffice it to say he was whole lot more upset about it than I was! I told him I intended to put stock bows on it anyway, and if desired the front bow could pretty easily be straightened so no real harm done, but he still moped a bit.

Regarding the 350 engine -
Once at Jason's shop, some ATF was dumped into each engine cylinder and left to sit. After a few days Jason called me and advised that he had the engine barring over by hand, and perhaps it wasn't toast after all. Shortly thereafter we dragged the truck into the shop and did a compression check on the cylinders, the results were bad enough that we didn't bother checking the 8th one, so it shall forever remain a mystery. I can't say I was disappointed, because I really didn't want any valid reasons not to replace that engine!

So, my 'spare' 6.2 was brought to the shop and set up on a test stand. It ran well, has good oil pressure, no problems found except a wonky starter and a leaky water pump, both of which were promptly replaced.

The 350 was removed and partially stripped down just to see the condition. Somebody had spent a lot of money on that motor, other than the water damage it was really nice inside. It is rebuildable, but for what that would cost I'd rather spend that on putting a diesel in.

Cheers

 

[M813rc]

As mentioned before, the engine came out of a 1991 Suburban, I bought it from a fellow SS'er in Corpus a few years ago.
As such, everything is 12v and I'm just going to leave it so, too many things to change/adapt otherwise to go back to 24v.

It came with all the fixtures, including alternator, power steering pump, and a/c compressor. All useful, since the M715 has power steering and power brakes on it already, and I'm sorely tempted by the a/c since this is a hard top truck. Having driven the M931 212 miles on Saturday in what ended up being 102* heat, the a/c is sounding reeeeally good to me right now!

The engine went into the M715 easily, requiring only minor modification of the 350 motor mounts. It bolted right up to the bellhousing already installed.
We found and ordered a four row aluminium radiator that will fit in the stock radiator slot. The new-looking two row radiator that came with the truck is inadequate for the diesel in Texas heat and has no oil cooler provisions, the four row has them built in.

My patched hood is back on the truck.

Next will be plumbing, exhaust, and rewiring. The current wiring looks like the ramblings of a drunken spider and the switches on the dash are just plain cheap garbage.

Cheers

Pictures
1 - looking pretty forlorn with no hood or engine
2 - engine and transmission as bought
3 - on the stand with new water pump and starter, pre-cleaning
4 - in the truck!
5 - Jason loading up on water, it gets hot in that shop
6 - hood back on, over the engine

 

[Barrman]

Your choice on the wiring but a M35 front harness works very well on a M715. There will be some extra blinker wire stuffed behind the headlights. But, it works.

 

[M813rc]

That sounds like an excellent option, I'll peek at Jason's parts truck today, or see what I can find at the convention. Your input is always valued, Obi Wan.

Cheers

 

[M813rc]

With all the travelling I've done in the last few weeks, including the MVPA convention (high quality show, great venue, pathetically small attendance) little has happened with the M715.
The priorities with this one are to get it operating in roadworthy condition, then start the cosmetic stuff.

My plan from the beginning was that the buffalo gooser bar on the front bumper would disappear, but that was set for "later" rather than "soon".
However, while we were installing the engine, someone (I won't mention Jason by name) made a somewhat ungraceful departure from atop the bumper and in the process got hung up on said buffalo gooser and darn near broke his leg. This raised his personal hatred for said bar, so he took out his anger upon it with a cutoff wheel. A little work with the grinder then removed most, if not all, sign that it had ever been there.

The front bumper itself is of high quality and made from heavy steel. You might notice, however, that in various pictures it sits at slightly different angles. That is because of the extremely poor way it was mounted, using bolts that are smaller than the holes they go through (except the one that isn't there at all), so it moves some. The mounting will be addressed in time.
As evidenced by the colour, the well for the winch holds water, so it will have to get some drain holes.

Cheers

 

[M813rc]

A little more progress...

The radiator has now been installed. It is a Luxerad unit designed for the CJ-7 with 350 engine conversion.
It has four rows and the required built in oil cooler, and fits perfectly in the factory mounting location.
There wasn't enough room between it and the engine to put the mechanical fan on (unless someone makes a shallow fan clutch unit that we failed to find) so the radiator has a shroud with two electric fans on it.

Various relays for glow plugs, fans, etc., and an auxiliary fuse block have been installed, along with a firewall mounted spin-on fuel filter assembly.

The previous owner had mounted a battery tray for a single battery on the front of the right wheel well. He had also added a cab heater unit from a civilian Jeep to the firewall, but this was in rather sad shape and rarely needed here anyway, so the whole thing was removed and the firewall holes plated over. This made room for a second battery tray at the rear of the right wheel well, so both batteries can be under the hood.
The in-cab stock M715 battery box so kindly provided by Barrman will now become a center console instead.

For the few times they are needed, I have had good luck with plug-in self contained heater/defroster units from the parts store (or Walmart, or...)

Cheers