Has anyone replaced the cummins NHC 250 with the 8.3 CTA?

[Tom Thumb]

Hi all,

I've searched and read a bunch of threads and have not found anyone discussing the actual removal of an NHC 250 and installation of a 8.3 CTA. It's hard to believe no one has done this.

Initial concerns are:
1) fitting the smaller 8.3 into the same space that had the 250. Do you need to fabricate new mounts? Does the radiator and shroud need to be moved backwards? What about the drive shaft length?
2) I'm told the military didn't change the drive train when they went to the A2s. What about the torque converter? Seems that the torque curve will be quite different for these engines?
3) What am I missing?

I did see threads regarding not allowing the hp to go over 350, and I saw threads discussing including pyrometer for the egts, which I will do.

 

[98G]

The torque converter is different for sure.

 

[Tom Thumb]

Good to know. Thanks 98G

 

[swbradley1]

I read 98G's post and thought he was being facetious and then I remembered that they put automatics with the 250s as well. I was thinking about my XM813.


I crack myself up.

 

[Gunzy]

If you source the engine from an A2 just get everything. T/C, eng and trans mounts, trans to transfer driveshaft and anything that is changed to the A2. Seems like a lot of work. Why not just buy an A2 truck? You can compare it all in the parts T/Ms to make the list of parts needed.

 

[74M35A2]

Rear mounts are universal to the flywheel housing, so that should (?) change over directly. The front mount cross member is unique to each engine, so you would need that. Not sure about fan spacing. 8.3 will double your fuel economy, and can be easily turned up in both power and RPM (speed). Only downfall is that it will sound like a school bus engine, well, because it is. 250 engine at idle sounds like it is going to pull your house off the foundation. 8.3 is actually rated at a higher power than the 250, believe it or not. I'm happy with the 8.3 in my 925A2, and I have not even turned it up yet. People that do say it drives like a completely different truck after. There should be a large weight difference between the engines also, so what about the front suspension springs? Starter is on different sides of those engines, but no big deal.

 

[Tom Thumb]

After talking to those military guys, who've done this, it appears this is a costly endeavor unless you do as was suggested above, get an A2 parts truck. So, now that I know all this, if anyone is interested in a re-built 8.3 CTA engine, let me know. I've got an extra one sitting around...I'm having it checked out and ran. I'll post a video soon.


Thanks guys for the thoughts...Maybe next time I'll ask before I buy...

So, now I'm thinking of putting a Cummins 400 with a turbo in there. This all started when I realized my truck does 20 up hills while the new big rigs are going 60...and I have no emergency flashers!!! Seems like an accident just waiting to happen...

 

[Cape Coastie]

You don't have the flasher tab on your turn signal lever? Mine has one on the original lever but it took me a little while to figure out how it works. My truck is a 1984 so it is pretty early.

 

[fuzzytoaster]

After talking to those military guys, who've done this, it appears this is a costly endeavor unless you do as was suggested above, get an A2 parts truck. So, now that I know all this, if anyone is interested in a re-built 8.3 CTA engine, let me know. I've got an extra one sitting around...I'm having it checked out and ran. I'll post a video soon.


Thanks guys for the thoughts...Maybe next time I'll ask before I buy...

So, now I'm thinking of putting a Cummins 400 with a turbo in there. This all started when I realized my truck does 20 up hills while the new big rigs are going 60...and I have no emergency flashers!!! Seems like an accident just waiting to happen...

You'll turn that allison into a metal slushy if you're not careful with that 400. It seems a 290 or 350 seem to be a better fit without the risk though I'd like to see a 400 in one of these trucks for sure!

 

[MtnSnow]

and I have no emergency flashers!!! Seems like an accident just waiting to happen...

Ohh Yes you do! In the Operators manual it explains how to engage them. But here is a quick insight to them. There is basically two styles of turn signal controllers on the steering column. One has two little "ribbed wings" on the turn stalk which you pull outward against and then move the turn signal stalk "two clicks" UP kinda like you are going to make a right turn but when you pull outward on the ribbed wings it allows you to move the stalk one extra position (this is the Emergency flasher position)

The other style has a small tab on the upper portion of the turn signal body. slightly press down on that tab and it will again allow you to move the turn signal stalk one more position up from the right turn position.

Enjoy

 

[Two Stroke Madness]

You'll turn that allison into a metal slushy if you're not careful with that 400. It seems a 290 or 350 seem to be a better fit without the risk though I'd like to see a 400 in one of these trucks for sure!

A 400 Big Cam would be nice, but I would ditch the auto in favor of a Eaton Road Ranger 9513. Then you could do the home brewed double overdrive conversion to make it a triple overdrive with last overdrive ratio in the high .5 range. Even if you do all that there's no telling if the transfer case would hold up to all that power. A 90 MPH 5-ton would be something to see though.

 

[Tom Thumb]

Ohh Yes you do!

Well it's good to know I have flashers. I'll check it out tomorrow.

A 400 Big Cam would be nice, but I would ditch the auto in favor of a Eaton Road Ranger 9513. Then you could do the home brewed double overdrive conversion to make it a triple overdrive with last overdrive ratio in the high .5 range. Even if you do all that there's no telling if the transfer case would hold up to all that power. A 90 MPH 5-ton would be something to see though.

I've been offered a good price on a 400 big cam turbo. If I can make it work without too much $$$, I'll do it.

That is if my wife doesn't divorce me first...She doesn't understand that yeah, I'm spending a lot more money than I thought, but hey, it's not every day you see a RV that can do 90 on the highway, be able to cross 5 foot pools of water, and finish a baja course all in one day! That would be quite an achievement! What do you think? Would the Mexican federalies allow a retired civilian owned military vehicle into their country?

 

[Thunderbird]

Oh, they'll let it in. Out might be a different story.

 

[98G]

90mph on what tires?

 

[Two Stroke Madness]

Well it's good to know I have flashers. I'll check it out tomorrow.



I've been offered a good price on a 400 big cam turbo. If I can make it work without too much $$$, I'll do it.

That is if my wife doesn't divorce me first...She doesn't understand that yeah, I'm spending a lot more money than I thought, but hey, it's not every day you see a RV that can do 90 on the highway, be able to cross 5 foot pools of water, and finish a baja course all in one day! That would be quite an achievement! What do you think? Would the Mexican federalies allow a retired civilian owned military vehicle into their country?

The Big Cam 400 will have an SAE #1 flywheel housing, you can use the one from the 250 but you'll have to machine the area for the camshaft bearing bigger. That and I believe the front motor mount may be different. Other than that I think it's plug and play.

 

[Two Stroke Madness]

90mph on what tires?

16.00's could take it. At least for a few minutes.