Thirst for Knowledge

First off I'm happy I found this website. I've read several topics and overall the people here seemed well informed. That being said this probably won't be the only forum I ask questions so here it goes.

I love the M715, fell in love with it (along side my 1978-79 Bronco full body) when I first saw it in the movie tremors. Yet with that love I've never really looked into it because I figured I'd never own one. Well, I'm writing a book and I find myself in need of the knowledge anyway. :p

1st question is this:
I know the original engine wasn't considered the 'best' due to it's overhead cam. From what I've read many say that most just didn't know how to properly maintain it, others say it was a horrible design due to lack of knowledge OF overhead cams. What's the actual story behind this as everything I've read have said the truck was phenomenal for it's time...except for the engine? Was the engine good and the issue was just bad maintenance or was the design bad?

2nd question:
What is the 'best' engine, pre electronic BS where you need a computer degree to work on it i.e. an actual mechanically driven engine, that one can put into the M715. I know best can mean many different things especially when you take into account what it will be used for, I'm not opposed to multiple answers as long as reasons can be given like better MPG, better HP, better Torque that kind of thing. I am asking in general overall.

3rd:
Site recommendations to possibly buy my own M715, whether to rebuild or straight up buy, I'm not shy. I already have a '54 Truck in my garage I'm beginning to tear apart to rebuild.

I put in a 77-ish 4 bolt cheby 350.

I figured in 30 years I would still be able to walk into NAPA and get what I need off the shelf.

Sent from my SM-G930V using Tapatalk

The 230 got a bad rap not because of the overhead cam (even in the early '60's, that layout wasn't exactly cutting edge), but because of oil leaks (the civilian version's front engine mount utilized the timing cover which would would distort over time and leak oil [from what I've read]) and the resulting oil starvation if the oil level wasn't checked & topped off. It also was easily over-revved, with predictable results.

The buddy I bought mine from (and with whom I built it up) had a bad taste in his mouth from a Jeep Station Wagon he bought that came off the showroom floor with a cracked head. He could barely stand to look at the 230 in the M715. I haven't heard this problem was endemic like the afore-mentioned, ones, though.

The biggest problem for the M715 was the time of service it entered. The truck was developed in the early 60's to replace the Dodge M37 which also only had a 230 in-line six cylinder, so that is what the Army specified for the motor for the truck. Unfortunately by the time it entered service in 1967, America's youth was into the muscle car movement and loved the power of big V8's. So what happens when you get a bunch of 18 year old draftee's who are use to driving muscle cars and hot rods, soldiers who drive the vehicles beyond the capability that it was designed for resulting in a lot of over revving and blown motors. During this time period, trucks, especially 4x4 trucks were usually very slow and underpowered compared to more modern trucks. They were more an implement than a passenger vehicle. Think more tractor than car. The intended top speed of the M715 was 55mph. which was an improvement of the M37's top speed od 45mph. If you have ever driven a stock M37 then you know that after 45mph the truck really feels like it's going to come apart at any minute which caused most people to slow down in them, but the M715 runs so smooth that young soldiers kept pushing them past the intended top speed over revving the motor. There is a pic here on the Zone from a member who was driving a M715 on the German Autobahn in the late 60's with the needle just buried on the speedo. This high rpm has a tendency to starve the cylinder farthest from the oil pump, #6 in the M715, which would eventually lead to failure. The military and Jeep tried to correct the problem by adding a governor to the motor mid 68' which helped keep the trucks from being over revved. And it worked, but the problem had already developed a reputation in the military and old timers labeled it as a bad motor and that has stuck to this day. I have both a 67' M715 and an 67' M725 in stock configurations and both drive like a dream and have plenty of power for standard back road driving as long as I keep them under 55mph. I have even had the M715 up to 65mph for short bursts, but would never take them out on the highway as they were never designed to run at those speeds for a sustained time. I also have a 53' M37 as well and can say that the M715 will run circles around the M37 any day in both comfort and power.

Was the engine good and the issue was just bad maintenance or was the design bad?
I think the engine is just fine if you use it within it's design limits. The biggest issue is the cost of rebuilding an engine. Parts are getting harder and harder to find, and some people want a mint for parts. I agree with Beast a lot of these trucks were abused or neglected and the engines suffered the worst of it all.

2nd question:
What is the 'best' engine?
What do you want it to do? People have put in fire breathing 454s, multiple diesels makes (6.2, 6.5, 4&6 bolts, Ford diesels), Lucky put in a fuel injected Ford 300, etc. Is this a putzing around truck or something else? I totally agree with Kaiser715. Chevy 350 with your choice of transmission is a great simple combo. You have to decide how exotic or original you want to go.

3rd:
Site recommendations to possibly buy my own M715?
You can find a craigslist searcher that does the entire US. I just did a google search of "M715 for sale" and had a large number of sites to check out. Some of the prices were pretty dang shocking, though! You can also put something in the Wanted ads below.

This site is by far the best informed group of M715 owners. And a very polite group of gentlemen as well. There have been quite a few variations of the Zone that changed due to updates or server crashes that you can search in the archives or the PseudoZone archives. They're sub-forums under the bigger general tech lists. Lost of great information to be searched there as well. Good luck on your search, and certainly feel free to ask any technical questions about the truck for your book- gonz

Thanks for the responses.

So in fact there was nothing truly wrong with the standard 230 outside of kids being kids (ie dumb) and poor upkeep/maintenance? (Not counting being under powered)

In regards to my 2nd question, I did forget to put in what it would be used for, sorry about that. For book reference I would say every day use like a truck should be used, hauling and getting to places that may include some rough terrain however considering what I've just been told I'd have to put in a caveat that 60mph top speed will not be adequate, though we're not talking 120. I'd say for book sake 75 would be top speed?.
If we're talking real life and I bought one I'd more than likely go full vehicle rebuild to spec and put a classic license on it.

I've done google searches and come up with sites but all the sites I find seem to be out of date, hence why i asked. The only one I've found that's reliably up to date is vintagemilitarytrucks.com, and to be frank i've never trusted craigslist, for some reason i feel like i would need to go heavily armed to any interaction considering all the stories i've heard.

Well, the axle gear ratios are a huge limiter for a higher speed. Since they're at 5.87 gears a lot of people put taller tires on for better top end speed. I had XLs (like 36" diameter) on my truck and my top running speed with a 6.2 diesel, Spicer 3053a overdrive transmission and a NP200 tcase was 62 MPH before the tcase got very very hot. To have a 75 mph truck, you would need to put in a new engine/transmission/tcase and either regeared/swapped axles or taller tires. There a quite a few trucks that people have done here, so they can pop up to let you know what they did.

As Gonz said, the 5.87 and the T-case are not going to appreciate the 75mph. I have 4.56s with 37inch tires and now use my truck several times a week as a daily commuter 25 miles each direction. I do have the option of backroads, but I do like to let it stretch its legs on the highway for about 18 of those miles each way. 60-62 mph seems to be a comfortable speed with the engine at ~2500rpm and my NP200 whistling away. My max speed was 75...feels like 175.

65 would work with what I'm going to be 'using' it for in my book, granted it's a book but I like trying to be accurate when writing about things when I can. When I said max that was red lined for short sprints not comfortable cruising.
So if I understand correctly from what eighty and gonz have said minor changes to the gearing ratio and tire size should suffice with what I'm wanting? Or does this include swapping out the engine for something a bit more robust too?

I guess this is as good a time as any to ask how one determines what engine can be put into something like this. Is there a site out there that compares engines to engine compartment size and the like?

Sadly...and happily...this is making me want to buy one more and more LOL.

I have seen tons of these posts over the years since I first got my M715 way back in 2004 and here is my honest opinion, take it for whatever. If you are looking for something to daily drive at highway speeds and would like some comfort, then look elsewhere than a 50 year old military truck. Besides the obvious things like low gearing and top speed, there are a ton of other issues that most don't realize until they start driving these trucks on a regular basis. There is no insulation in the cab, this means that they are hot in the summer and cold in the winter, plus they are very loud. Yes you can put carpet in the cab or the peel and stick insulation under the cab to help, but just be aware that you'll likely never take care of all of it. Plus with the open top design and fold down windshield, these trucks leak and the old joke in military vehicles is that when it rains the driver always ends up with a wet foot somehow. This is why you find so many of them with rusted floors and rockers. Plus parts availability can be difficult, besides stuff like the motor and drivetrain, there are tons of parts that can be hard to find replacements for. For example the one door seal is imposable to find new, there are tons of the otherside seals but none of that side available. Tailgates are extremely hard to find if missing or damaged and when you do find one, expect to pay big bucks for it. Look I'm not trying to talk you out of a M715, as a matter of fact I absolutely love mine and drive it whenever I get a chance. But just trying to put a more realistic view on it.

The weakest links in the 230 design are...in my opinion...

1. The external oil line on the back of the head to feed the head...its hard to get at to change and does love to leak...replacing with braided stainless line or solid metal...like brake line...is THE way to go.

2. The cam oiling is a bit weird overall...keep the oil CLEAN and problems wont happen there.

3. Exhaust manifolds like to crack...keep the exhaust pipe holders all in good shape and make sure to NEVER overtorque the manifold nuts.

4. Valve cover gaskets like to leak...if replacing one, work slow and careful to get it on and NEVER overtorque it.

5. The ignitor...distributor and coil assembly...is steel on the outside of the shaft and the timing cover it goes into is aluminum...they love to weld together. Take out the unit and clean any corrosion off the shaft and out of the hole...then reassemble with anti-seize compound on the shaft to keep it from doing it. If you need help getting it out because it is frozen, just ask!

6. Rear main seal leaks. You can change it, make sure not to line up the ends of the seal with the horizontal parting line of the block and filler block...that will make it leak more.

7. Oil pan gaskets tend to leak...good news, its easy to drop the pan without having to take other stuff apart.

8. The clutch is a pain to change, the bellhousing is difficult to get off...hopefully you dont have to do it, it is challenging to say the least.

I also forgot to mention that I do not have the stock 230. I swapped in a fully rebuilt 318 with a NP435 transmission.

Yes it’s loud, hot, sorta uncomfortable, but I can’t get enough of it.

Quote:

---

Originally Posted by Beast

The biggest problem for the M715...There is a pic here on the Zone from a member who was driving a M715 on the German Autobahn in the late 60's with the needle just buried on the speedo. ...

---

He is right, Guilty as charged. My truck in Germany.

But I wouldn't think of doing it to my truck here in Florida. Those 230 Tornado engines were just fine. I love it and have no desire to change to another type.

But that doesn't mean that I do not like what others have done. At 72, I am just a "Stock" guy and strive to keep it as close to original as possible.

Holey crap that's suicide!!!!!!! Gotta be 90+ !!!!!:eek:

Quote:

---

Originally Posted by teking

Holey crap that's suicide!!!!!!! Gotta be 90+ !!!!!:eek:

---

That is a true photo, I took it in 1970 on one of our trips on the autobahn. The truck was a little over a year old, burned a lot of oil but ran great. No "Death Wobble" of the front tires.

Side note, when the tires were worn, the Motor Pool put recaps on it and didn't balance them. Talk about shaking! I "procured" four new Goodyear tires and put them on. Back to driving good again.

Also, I was 22 years old and not as careful as I am today at 72. But I still have an M-715!