Cummins NHC 250 vs 6CTA 8.3 opinions - Steel Soldiers::Military Vehicles Supersite

Cdub · 05-28-2007, 16:30

Hey Guys,

Since I've never owned a vehicle with either engine.
I would like you to let us know your experiences with
either engine. Something like this...........

Cummins NHC 250

pros / cons...........(likes or dislikes)

Cummins 6CTA 8.3

pros / cons...........(likes or dislikes)

Lets leave this as open as possible........anything from

Fording
Cold weather starts
Power
Speed
Reliability
Gas mileage
heavy loads
repairs
parts

List anything that comes across your mind about either or both the NHC 250
or the 6CTA 8.3

I'm sure the answers will surprise even the best of us......just have fun with it
and see what kind of answers we come up with.

Cheers,

C'dub

BKubu · 05-28-2007, 17:29

NHC-250
PROS -- parts availability, reliability, strong motor (not necessarily stronger than the 6CTA motor, but you get your power from 855 CI's, not the turbo)
CONS -- does not like cold weather (it will always start, but you will need some ether), older design so it is not as efficient fuel-wise

6CTA 8.3
PROS -- about the same power as the NHC-250, but it is produced by a much smaller and more modern power plant, whisper quiet (for those of you who like throaty motors, this one is not the one for you...it is almost as quiet as a Duramax), turbo if you like the whistle (but it is not a whistler like an LDT-465-1 C)
CONS -- parts availability, starts better than the NHC-250 in cold weather but still needs a sniff of ether

I've had both NHC-250-powered trucks (M929A1, M928A1, M932) and 6CTA 8.3-powered trucks (M936A2, M932A2 and now two M925A2s). While I love the 6CTA 8.3 motor, I would suggest that anyone who is interested stick with the NHC-250-powered trucks. This has much to do with parts availability. The parts for these trucks are not readily available. While this is true of all M939 series parts, it is even more the case with any parts that are A2 specific and the motor is one of those items. Beyond the 6CTA 8.3 motor, the A2 has a different cab, different air-intake plumbing, some different exhaust parts, different axles, CTIS parts, and probably some other stuff that I am not thinking about. I know some guys in active service have told me they would choose a straight M939 series truck or an A1 over an A2 any day. This has much to do with the perceived lack of power with the 6CTA motor and the poor CTIS design. With that said, I've owned some brutally strong A2s. I had an M936A2 that literally forced your butt back into the seat as it shifted through the gears. Remember that the M936A2 weighs over 37,000 pounds!

My $.02...

WillWagner · 05-28-2007, 18:40

Bruce, I say nay on the parts availability. Parts for the C are very easily had. If you need some and can't get any help, please let me know. As for the power, although they are almost the same HP, 250/290, there is no substitute for qubes. Torque is about the same, but I still feel that the 855 will still hang better on a long hard pull then the C. 505 CID, vs NH/NT, 855 CID.

BKubu · 05-28-2007, 18:52

I suppose I shoudl clarify. I meant parts availability on the surplus market. Yes, the 6CTA parts are available...especially since it is a more recent motor and is used in many civilian commercial applications...but it gets pricey going to Cummins or other commercial parts suppliers. Compare that to calling John Winslow or Sam Winer for NHC-250 parts. I will keep your offer in mind if I do need 6CTA parts in the future. Fortunately, my motors are running well at the current time and I don't foresee needing anything other than maintenance items.

Cdub · 05-29-2007, 22:16

Bruce, what can I say.......

......." That was just superb "......

Coooool........Thanks

C'dub

steelsoldiers · 05-30-2007, 12:05

Not that any of you would do this

but as far as bumping up the power goes, the 8.3 CTA would be a better choice. There are already aftermarket injectors, fuel plates, injection pumps, etc... available for the 8.3. You can safely increase the boost 15-20 psi to handle the extra fuel without worrying about head gaskets. The aftercooler will help keep the temps down. The P7100 injection pump is tough and very adjustable.

Usual disclaimer: add boost and EGT gauges before you start tweaking. Anytime you increase power, other parts downstream may suffer (ie the tranny, driveshafts, axles).

All that being said. I plan on keeping mine just as issued, well maybe with the exception of boost and EGT gauges, which should have been issued

moose · 12-11-2010, 01:47

I was just about to post this exact thread, glad I checked. Thanks to all who contributed and Cdub for posting it. I was hoping that more people that have experience in both or one of the two would give us their 2 cents. I have looked and seen a lot of aftermarket support for the 6cta, Banks even makes a power pack for this motor. I guess it is also used in motorhomes and mid-duty trucks in addition to its commercial uses. I am looking for a m928, and they come with both engines which is why I am interested in what you all think about these 2 engines. Basically, which one would you rather have and why. Thanks again for anyone that contributes.

Flat Black · 12-11-2010, 11:40

CTA motor all day every day and dont buy anything from Banks, its over priced junk. There are much better choices out there for ISB and CTA Cummins parts.

Look at the drag racers and sled pullers (running those two motors) and I can promise you NONE of them are running Gale's crap.

There is a replacement for displacement, its called boost. A very mildly built CTA will get you 400hp and 1200 TQ. If that's not enough call Scheid Diesel and open your wallet - a 700hp/ 2000 TQ motor is not far away.

A CTA is not new tech by any means, but newer than the NHC, which is basically BCIII tech from the 70s. A 14 LITER motor making 250hp is a joke. (would you drive a new Honda Accord with 35hp?? - no one else would either) Mechanical CTAs were made into the mid 90s at least and that is the motor you want for sure (Bosch P7100 injection pump). The CTA's may have been made longer and the newer electronic versions (ISC/QSC) are stout as well.

These engines have been used in tons of applications and there are plenty of sources for parts (other than Cummins dealers)

.02

emr · 12-11-2010, 14:28

Well alot of opinion, here, and alot of facts, sayin someone would not buy a 35hp honda, is an opinion, if it was a historical and hobby oriented thing the answer is , Yes. the 250 is a bullet proof motor in service a very long time and no major problems in the line in any unit I know of, of truck units that run or ran these, in fact alot are still strong in service, the ct motor is like well bruce said it best, different but very close . The 250 is quite up to the task when in low range just like most military motors, non of the motors we are dealing with are new tech, it is good to remind people what they are getting into, its a hobby. for those working these trucks I would still rather have the 250, but someone else may not....randy

wreckerman893 · 12-11-2010, 16:48

Having had a 250 that ran away (long story) and almost self-destructed I can tell you that getting parts is not a walk in the park.

I had to buy an engine just to get pistons and liners out of.

I tried several Cummins dealers in Alabama and all of them said that the 250 is an "obsolete" engine and most dealers do not stock and cannot get (from Cummins) parts for it.

I ended up selling the wrecker to a guy that ran a scrapyard and towing service....he told me he had a ton of money in the engine before he got it rebuilt (using his own mechanic).

It can also be a real pain to find an old school diesel mechanic that can work on the 250's and make the run right.

I would go with the newer engine.