Engine questions

[hobie237]

Ok, I'm sort of, well, completely new to the M715. I tried searching for a couple days, but, well, I suck at searching. Anyways, I have a few questions.

As background, I'm looking to get into an M715 for primarily off road use. Not like extreme rock crawling or anything, just the ability to go pretty much anywhere I want. I really like that they have a straight 6, there's just something cool about them.

I'll most likely end up keeping the stock engine for quite some time, provided I don't read anything that makes me too suspect of its durability. If it does go, however, I'd like to put in something newer that's ideally another straight 6. Anybody put in a Jeep 4.0L? How well does it go in? I know the wiring would be a pain, but aside from that, anything I'd need to know?

If it's too much of a pain, I think I'd just end up going with a Ford 300 straight 6, which, as much as it pains me to admit it, is a fantastic little engine.

I'm not looking for something super powerful. I'm just looking for something that will start and run reliably in temperature extremes (both high and low) and altitude extremes (again, both high and low) without undue drama, and make decent, but not huge, power, that doesn't leave me stranded on the trail and that won't cost a fortune every time I need to do a tuneup.

Suggestions? Thanks.

[Barrman]

Welcome.

Most of us went with V8's once our stock engine gave up because they are plentiful, cheap and powerfull. Plus, OD transmissions can be bolted to them.

The Jeep 4.0 will be more costly to go find and install compared to a V8.

The Ford 300 is a great engine and has been swapped into many M715's. So has the Chevy 292. A fuel injected Ford 300 requires a few firewall mods, but has been used with great success.

[randyscycle]

The biggest issue I can see with a 4.0L swap would be a lack of a stout enough transmission. Anything the 4.0L was installed in factory was generally a light vehicle, whereas the the 715 is around 5500-6000 lbs. There may be an adapter out there to add something a bit more substantial behind it.

As far as the engine, with the 715's gearing, it probably would do pretty well. The fuel injection would be an added bonus in my opinion too.

[Swampthang]

Doesn't the 4.0 share the same pattern as a 258/360? If so then a T-18/D-20 combo from a J series would bolt up to it.

[hobie237]

Hm, I'll have to keep thinking about it, and looking into what can be done with the stock motor, as that's the obvious cheap/easy choice.

[Mikel]

The biggest issue I can see with a 4.0L swap would be a lack of a stout enough transmission. Anything the 4.0L was installed in factory was generally a light vehicle, whereas the the 715 is around 5500-6000 lbs. There may be an adapter out there to add something a bit more substantial behind it.

As far as the engine, with the 715's gearing, it probably would do pretty well. The fuel injection would be an added bonus in my opinion too.

The AX-15 is a pretty robust light duty transmission that does very well behind 4.0's. Given the very low gearing of a M715, I would venture to say that a AX-15 shouldn't do too bad.

[Jester]

Unless you were going to FI, why would you bother to swap in another straight 6 with basically the same power as the Tornado?

I plan on running the 230 Tornado until it dies, then worry about a "upgrade".

[hobie237]

Fuel injection has other benefits besides power delivery- like altitude and temperature compensation.

[Mikel]

Unless you were going to FI, why would you bother to swap in another straight 6 with basically the same power as the Tornado?

I plan on running the 230 Tornado until it dies, then worry about a "upgrade".

The 4.0 is a great engine. Great power and low end torque, and bullet-proof.

[glenn]

I thought about a jeep 4.0 too. You can get bellhousings that will bolt to the stock trans I believe from Advance Adaptors, would probably have to change the input on the trans though. The Jeep 4.0 has a crank sensor that bolts to the back of the engine and measures off the flywheel. There are kits to move it to the front of the motor though. Painless makes a wiring kit/engine management system for swapping in some years of Jeep 4.0's. Where I live you can get the 4.0 cheaper than a fuel injected V-8 at the junkyard. I know the 4.0 will go a lot of miles before needing a rebuild. You could always go with a stroker 4.0 if you want more power. Of course all this won't be cheap. Any fuel injection/engine swap seems to cost more and have more bugs to work out than you expect. Probably the cheapest and easiest fuel injected set up would be a chevy TBI V-8 unless you already have scored a parts rig for cheap or nothing. Of course it would be cool to swap a Jeep engine into a Jeep vehicle, usually their engines are swapped out for another brand. My second M-715(non-running) might get a 4.0 in a couple of years when my son starts working on it. I plan on putting him in something big and slow for his first car.