5 Ton 290 Big Cam Swap

[ryanaubra]

Well, here it goes. I got almost everything i need, with the exception of time, to start my 290 big cam swap. I got this truck with a "Engine will not start" rating from Kansas. Picked her up for a song on GP. Got it home and realized it had main or rod bearing that was a little too tight on her re-build. It ill turn a 1/4 turn and then stop. So, the verdict was to swap it for a little more power.

She started out as a 923. The truck is virtually new, with 0 miles on the odometer and 9 hrs on the hour meter. Every inch of the truck is straight, rust free, and clean as a whistle, with the exception of the oil! I plucked the bed to remove one of the lockers from the rear axle to sell and fund part of the build. I am 86-ing the back axle anyway for now to do my bobber.

I found this 290 cummins (literally a barn find) and off to the races I go. I figured i would start this thread and hope to get any pointers and give any pointers that i can along the way. I have talked to a few of you out there that have done it and am ready to go. After the motor comes bobbing, crew cab, air bags, Axletech 4000's, 53" michelin's and a few other mods i have in mind. It ought to make for an interesting year! I look forward to getting any feedback i can from all of you and may need some help if any of you are not doing anything!&$! Oh, i have a crystal clean NHC250 I am parting out. Let me know if you need any parts! Also will sell whole. All you would need to do is possibly one crank or rod bearing and she is ready to go.

 

[ryanaubra]

Got the hood off, all the various and sundried items off of the motor, the trans dropped, ready to separate the motor from the bell housing. Not much more to report today, just a little progress on the tear down.

 

[Scar59]

PM sent, could use some small parts.

 

[Jakelc15]

I believe your bellhousing needs to be shimmed to have 0 runout with your flywheel.
Looks like a good swap. Keep those pics coming!

 

[ryanaubra]

Thanks for the tip. Planning on swapping bell housing and everything from 250 onto 290 and running the Automatic. The 10 -speed swap is a bit too industrious for now. Would it still need to be shimmed? Thanks.

 

[Jakelc15]

http://www.manualslib.com/manual/809857/Cummins-N14.html?page=95
Your original parts are probably within spec anyway but it's easy to check. Probably matter more with a clutch.
10 speed

 

[ryanaubra]

Sweet. Thanks for the tip! I'll check it out.

 

[Csm Davis]

Can the front engine mount be swapped from the 250 to the 290 ? Why not if no.

 

[ryanaubra]

I have researched and found some who have cut the front mount and fabricated a custom mount (photo courtesy of A&H Recon - thanks for the help!) . I have not been able to find any evidence of these 250 mounts breaking. I know the 290 will have a ton more torque and power, but the rear mounts absorb the majority of that. As far as i can tell now the 250 mount will bolt up. I am going to gamble on the 250 mount being fine and go with it. I am not going to be pulling a trailer or anything crazy with it, just a toy.

 

[JohnnyBM931A2]

Another bobber.. <sigh>

 

[Csm Davis]

Hey Ryan that mount looks like a 8.3 mount

 

[ryanaubra]

Don't know if you can see the mount in the picture. That is the factory mount from the Big Cam. This was in a Western Star cab-over.

 

[ryanaubra]

Here is the big cam mount. I should be taking the 250 out tonight and will do a side-by-side comparison.

 

[ryanaubra]

We got the motor out and on the ground last night. There were some questions both in my mind and from some of you about the motor mount interchangeability. You will see from the picture that the 250 mount is considerably different than the 290 mount. Also, there has been some talk about the 250 mount being weak. Let me tell you, the 250 mount is a stud!

Based on the way the 250 mount is mounted around the crank, the torque transfer to the mount is almost eliminated. The mount has a rubber bushing in the center to cushion, so any torque on the front mount [the torque is about a smaller moment arm due to the close proximity of the center of rotational mass i.e. crank ] should be essentially absorbed by the circular mount.

My mechanic tells me that we can pull the cup that the harmonic balancer is attached to off the end of the crank and swap to the 290 and run the 250 mount on there. We'll see how that goes. Hopefully going to fire the 290 up this afternoon on the engine stand!

And oh btw, there is exactly 1/64" of clearance in all 3 axes to get that motor out with the bell housing still on it. Tight!

 

[ryanaubra]

Ok. It was a long Friday + weekend on the build. we hit every roadblock that is possible and eventually called in the big guns. The guy i am working with works for a heavy truck dealer/mechanic and knows some people who know cummins motors from 30+ years of working on them day in and day out. With that being said, here is what all I learned this weekend:
1. Big cam and small cam motors have more differences that I was able to see on the surface. My original plan was to take the motor and swap all of the parts from the existing NHC 250 onto the big cam motor and make it an easy hook-up..... wrong! The overall block looks the same, and is the same, but it is not....I'll explain
2. The front motor mount is different.
3. The harmonic balancer offset and therefore alignment of all the pulleys and accessories is different.
4. The water pump, oil cooler, water neck, thermostat housing, etc... all different.
I could go on but i will spare the details.

In a nutshell, the 290 swap is on hold and after much discussion with professionals and visual confirmation for myself, it was determined that the NHC 250 motor -get ready for it ------ DOES HAVE PISTON OILERS!!!!!!!!------ I'LL REPEAT ------ DOES HAVE PISTON OILERS!!!!

Not to mention - if you have never pulled the oil pan off of a 250 motor and see what it looks like.....there is 10 gallons of oil in that motor at 60-80 psi.....you could lay down and take a nap in the space between the piston/rods/crank. Unless there is no oil left in the pan, the crank should sling enough oil to get the job done, without the oilers. The "experts" (i.e. seasoned professional diesel mechanics)I spoke with all said that as long as i do not get my egt's above 1100 degrees it will run perfectly for as long as i need it to.

So, luckily, i happened to have a freshly rebuilt, in-the-can 250 that was just waiting to be modified. So, I am going to be the guinea pig for all of you out there who have talked about putting the turbo on the 250 and have gotten conflicting information from multiple sources. Here is the new direction for my build:

Still going to crew cab, bobber, eventually Axletech 4000, etc.
Fresh rebuild NHC 250
Exhaust manifold, turbo
Aftercooler intake from Big Cam 300 set up on its own closed coolant system with its own radiator and thermostatically controlled electric pump
Intercooler
Real deal Jakes on all three heads
Pyrometer and boost gauge
Tweaked early injection pump with no boost compensation.

I am going to save the 290 for another project for a rainy day! If any of you out there are like me, you want to get a little more oomph out of your 250 but have been reluctant due to the fear of grenading it on a Sunday drive. Well, hopefully my hard work will dispel some of the myths and get you on the path to black smoke and turbo whistle before you know it. More to come.

 

[Shoprat 19th Engr]

Just remember to dial the bell housing in to the crank + or - .010 so the clutch will work freely

 

[Jakelc15]

I want to see pics of your 250 oil squirters. And you definitely aren't the first to put a turbo on a 250.

 

[Csm Davis]

Yeah here's a good thread or two.
http://www.steelsoldiers.com/showthread.php?t=28133

http://www.steelsoldiers.com/showthread.php?t=79077

 

[11Echo]

Another bobber.. <sigh>

This is the " 5-Ton Mods and Hot Rodding " forum.

 

[ryanaubra]

I know I am not the first one to do this swap. I have obviously read enough back and forth on the issue. The problem I have with it is there is always two sides to the story. Some people say - no it won't work and you are going to blow your motor blah..blah..blah... but never seem to have any real data on the subject, just repeating what they heard the last guy who didn't like changing a 5 ton said. The only real proof i have seen is the few who have done this swap and claim to get the awesome results, as long as you watch your EGT's. That is a no brainer. If your EGt's get too high on any motor then something bad is going to happen.

Let's get crazy for a minute and think about logic..... Why would Cummins and Uncle Sam re-design a motor and incorporate a flaw - i.e. remove piston oilers - and make thousands and thousands of them for use on both the civilian and military market. It doesn't make sense. I am no diesel expert, maybe I am putting too much stock in listening to the people who do get paid to build/service/repair/modify/hot rod diesel engines for a living, some for over 30 years? When they say to me that the engine has piston oilers then i tend to believe them.

With that being said, i am going to call a spade a spade and say that if you have a problem with someone doing a swap, modifying a 5 ton, bobbing, whatever, skip over the forum entitled "5-Ton Mods and Hot-Rodding" because it is likely to contain elements of exactly that. I have enjoyed reading the posts and liked the sense of help and good advice that most of the people on here give. That is generally what forums and "chat rooms" are for - help. That is exactly what i am trying to do - help anyone else out there who really wants to do the swap but was reluctant because of the evident dichotomy of opinions out there with very little facts. If i grenade the motor the first time i hit 30 mph, then i will figure out why, make a note about it, and try and let anyone else who may be considering doing the same thing not to do what i did because it did not work. Hopefully I will eventually have some useful information come out of this with some facts/data/pictures/results to back it up. That way the next guy who is considering doing the same thing may find it helpful to accomplish his goal.