Builds 68' M715, AKA "Smokey" (Can I post this Jeep on MUD?) (3 Viewers)

[Rock40]

It’s done.

Unfortunately, picking this up with the forklift like they did proved to be unwise. The rear shock cross member completely crushed and bent. It was likely coming out with the links and coils anyway but I wasn’t too happy about it. In the end it turned out OK as I worked a deal for the blaster to take the stock M715 axles and blast the cab for free. Looking at the frame, it still appears straight, I’ll confirm at a later date and correct if necessary

 

[Rock40]

Cab back in place....

 

[Rock40]

Drivetrain mock-up today....

The 8.1 liter is HUGE. With this spacing, I believe I can squeeze a radiator in. If not, the firewall will need a bit of massaging to get the engine rearward a bit more.

Popped a Saginaw box on the frame. The stock M715 steering box was full manual. Looking at the input on the box, I think the steering shaft will likely need to be a two piece design with a pillow block bearing. It'll go though.

Looking down at the SM456 from the cab. It lines up well with the Ranger OD in front of it. Of course the floor is going to get modified for the 5 shifters required for the drivetrain.

 

[Rock40]

So sweet! There's room enough as is to more or less have a flat belly. The SM465 is about 3/4" below the frame rail and the NP205 is about 1/2" low. Better then I was expecting and I guessed on the ORD Magnum clocking.

Green paint mark on the very lower edge of the NP205 shows where the belly would be completely flat.

Showing the centered drivetrain between the frame rails.

 

[Rock40]

Problem areas. The biggest issue is the front differential housing. Not really fair because the M715 axle won't be used but I suspect the same for the ProRock 60. Maybe worse due to the high pinion.

There is very little room between the oil pan and differential housing. Granted, the engine could still be moved up in the frame rails some but want to keep the center of gravity low along with the lift. At this point, I'm considering mocking up the stock GM Kingpin 60 to see it relates. Probably will next week. Overall, things could be a lot worse trying to get this much drivetrain in a 50 year old truck.

 

[WesternCruiser]

Looking great, Ross! I'm very interested to see where the stock Dana 60 differential will land (the modern kingpin version), as a starting-point; between that and having a Pro-Rock example on hand, it should be easy to see how close things will be. It IS nice to see those spool stands in use--glad we didn't toss them! That Magnum looks like it'll make adding a cross-member very easy, which is nice. Great work!

 

[Rock40]

Stuffing an engine this damn large into an engine bay designed for an inline 6 is proving to be...challenging.

This is the passenger side manifold. As is, it's mashed into the firewall and the engine REALLY needs to move back some more to be able to run a radiator/fan combination capable of cooling this beast. Prior to this pic, I added a slightly larger that 1" body lift to help alleviate things some. The EGR bit is really the issue as the manifold is longer to incorporate it. The options were hacking into the firewall bigtime or modifying the manifold...

Drivers side manifold, because it lacks an EGR port on this side, clearance is not an issue.

Modified manifold with the EGR port deleted and the flange turned down (toward the ground) about as far as I could. I'm hoping there will be room now once the firewall is clearance/modified so that the valve covers/heads will fit.

The plan is to have a professional welder friend of mine put the manifold back together with some silicone bronze. We'll cross our fingers and hope it holds.

 

[Rock40]

Firewall modification day...

Making some cutting marks

Ultimately this should be close, very close. The engine has been raised about 2.5" inches and pushed back about 1.5" inches. There's now approximately 7" of room for the fan and radiator combination.

 

[Rock40]

The plan is to pull the engine back forward about 1/4" from where it's currently at. That'll make a bit more room between the firewall and exhaust flange so the floor isn't getting cooked.

These are the cuts, they're not cleaned up yet but overall, not too bad

 

[CreeperSleeper]

Just cut it all out and build your own firewall...

 

[Rock40]

Just cut it all out and build your own firewall...

There is a real danger, don't tempt me...

 

[CreeperSleeper]

Hahahaha! It's amazing how easily things can spiral out of control. It sure looks like a tight fit! I'm interested to see how you design it to keep the engine cool and protect the passengers from radiant heat.

 

[Rock40]

Yeah, it'll be a trick. The plan is to place some sort of radiant material (Dynamat or similar) on both sides of the firewall to prevent cooking. The floor of my 40 gets so hot on long road trips that I have to wear sandals in the cab to keep my feet ventilated.

 

[Rock40]

Started the fab for the rear crossmember which will mount under the Dana 300 AA adapter. 3/8” for the main plate, 1/4” “wings” followed up with 3/16” wall 2” square tubing.

The plan is to TIG weld this all out to ensure good penetration and hopefully less warping

Drivers side leg is now done. Frame will be scab plated as shown. On to the passenger side now which will be a bit tougher given the fact that the mount needs to clear the front driveshaft

 

[Rock40]

Plugging away....

Removed the awful dual battery mount behind the drivers seat which was obviously a military “addition” at some point. Most of the bugger welds actually burned through the cab. Found a lifetime of crap under it

Also fixed the poor VIN plate

View attachment 1668658

 

[Rock40]

Crossmember complete....

 

[Rock40]

The level approximates the front driveshaft, since the drivetrain will all be above the frame, the crossmember needed to go up and over the front driveshaft

 

[jlclar09]

I have a 68 M715 and I am also getting ready to install an 8.1 Vortec in mine. I currently have a 350 SBC and SM465 in mine. I am debating on using a ranger box like you did and keep the SM465 or use the Allison 1000 that is in my donor truck... decisions... looks great!!!

 

[Rock40]

I have a 68 M715 and I am also getting ready to install an 8.1 Vortec in mine. I currently have a 350 SBC and SM465 in mine. I am debating on using a ranger box like you did and keep the SM465 or use the Allison 1000 that is in my donor truck... decisions... looks great!!!

Cool! sounds pretty similar. Depending on your tire size, I'd seriously consider an overdrive either with a Ranger or the factory transmission. This project is still slowly moving along, I'm just a bit bogged down with other projects that jumped in front of it for the time being.

 

[Rock40]

Time for an update:

Donated the old M715 axles to the blaster in exchange for some free work

Got the cab blasted. Not too bad overall for 50 year old metal