Cummins NHC 250 vs 6CTA 8.3 opinions

M923driver · May 13, 2012

Take into account the condition of what you're buying. You're probably not going to need to go through a motor anytime soon if your get a low mileage/hours unit right from the get-go. Parts are available on the net for a model A Ford or my 1950 Chevy, you'll find parts for the 250, but it'll be harder than the CTA. Also, I love the torque band of the CTA, pulls really strong all the way to top gear. Buy the best truck you can find, hopefully a mid 2000's rebuild that will serve you well for a long time.

ModernDieselLegion · May 14, 2012

granted im in houston, but to all the people who think these parts are hard to come by..... dont go to cummins for this stuff as they rarely have an interest in 50 year old tech.

If i was in houston id go to stanley or m&d or somethin. i walked in and they had a full overhaul for me on a palate(from sleeves and pistons to every overhaul hard part) after about 5min in the back. im pretty sure with sleeves it was under 900 even...

i really want to put my extra Cummins turbo 6.7L common rail and NV5600 6 speed in our deuce when it gets here. it makes around 900hp and 2000ftlbs right now. should be fun at the offroad park.

73m819 · May 14, 2012

ModernDieselLegion said:
granted im in houston, but to all the people who think these parts are hard to come by..... dont go to cummins for this stuff as they rarely have an interest in 50 year old tech.

If i was in houston id go to stanley or m&d or somethin. i walked in and they had a full overhaul for me on a palate(from sleeves and pistons to every overhaul hard part) after about 5min in the back. im pretty sure with sleeves it was under 900 even...

i really want to put my extra Cummins turbo 6.7L common rail and NV5600 6 speed in our deuce when it gets here. it makes around 900hp and 2000ftlbs right now. should be fun at the offroad park.

Should be hard on axles, drivelines

Squirt-Truck · May 14, 2012

Just curious, what is the duty cycle of a 6.7L at that kind of power? Do you measure it in seconds or minutes or just really low percentages?

CraneTruck had a real neat comparison a few years ago on duty cycles for these newer high output engines.

tobyS · Mar 23, 2014

Hi guys...This is an interesting read. I started a thread for "road truck" that has led me here. I would like to make a higher speed truck, using Cummins engine, Allison tranny and frame from a 923, probably a school bus rear end and front end.

I have never built either engine, but it would seem that either should start with crank, rod and piston balancing and upping the R's a bit. Is that possible?

As for air...and doghead has pointed out it is much inferior to a turbo or blower... on the 250...how about an electric (24vdc, 1.5hp) blower with variable speed? I'll try and find some info on the amount of oxygen under 15-20" vacuum and compare to 1-2 lbs of positive pressure. In working with sawmill dust, I move a lot more under pressure than vacuum and have to think the same would be true on the natural aspiration 250 engine (for modest gain).

hailstone · Oct 21, 2014

if you want to go to a turbo and after cooler Why not just find an older 290 Cummins? Back in the 70's that the the engine before the NTC 350's. JMO

Moto2four · Oct 21, 2014

tobyS said:
Hi guys...This is an interesting read. I started a thread for "road truck" that has led me here. I would like to make a higher speed truck, using Cummins engine, Allison tranny and frame from a 923, probably a school bus rear end and front end.

I have never built either engine, but it would seem that either should start with crank, rod and piston balancing and upping the R's a bit. Is that possible?

As for air...and doghead has pointed out it is much inferior to a turbo or blower... on the 250...how about an electric (24vdc, 1.5hp) blower with variable speed? I'll try and find some info on the amount of oxygen under 15-20" vacuum and compare to 1-2 lbs of positive pressure. In working with sawmill dust, I move a lot more under pressure than vacuum and have to think the same would be true on the natural aspiration 250 engine (for modest gain).

Finding an electric blower that moves that much air at 100% duty will be impossible. And IF you found one, I'd bet it's amp draw would be in the hundreds.

EMD567 · Oct 21, 2014

All I know is that my M814, loaded to 32k on the tires, will walk away from deuces going up hills. Fast? **** no. But I will climb in that beast, and go to the left coast with out a thought.

PyroJoe · Feb 3, 2022

I noticed there were 2 or 3 posts on here talking about the P7100 and the 6CT. The M939A2 DOES NOT come with a P7100. It has an MW pump, similar to that of the early 90's DT466's. You don't "just grind a plate" or "slide a plate forward" and gain 100hp. @Neverenufhp has a lot of videos on how to adjust the MW, but the power potential is not there from factory like it is with the P pump.

DeMilitarized · Feb 3, 2022

PyroJoe said:
I noticed there were 2 or 3 posts on here talking about the P7100 and the 6CT. The M939A2 DOES NOT come with a P7100. It has an MW pump, similar to that of the early 90's DT466's. You don't "just grind a plate" or "slide a plate forward" and gain 100hp. @Neverenufhp has a lot of videos on how to adjust the MW, but the power potential is not there from factory like it is with the P pump.

It may be true but on a stock turbo the MW pump will give you more than enough power. You will have the ability to melt pistons with the stock turbo.

Cummins NHC 250 vs 6CTA 8.3 opinions

More options

M923driver

New member

ModernDieselLegion

New member

73m819

Rock = older than dirt , GA. MAFIA , Dirty

Squirt-Truck

Master Chief

tobyS

Well-known member

hailstone

New member

Moto2four

Member

EMD567

Driver for the Ga Mafia

PyroJoe

Member

DeMilitarized

Well-known member