Cummins NHC 250 vs Mack ENDT 673

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sandcobra164

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I have a quick question. Are these two engines anywhere near the same ballpark in regards to horsepower and torque output? I know what is in the manuals but can they be tweaked reliably to perform basically the same?
 

fuzzytoaster

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The 250 is going to be cheaper to acquire and more practical to find parts for. I can't speak on a side by side comparison but the 250 would be a more logical choice.
 

papabear

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Joe you have driven Proud American many times. She has the Mack ENDT and I'm sure you will agree she is powered right. I also have/had several 250's and I believe the Mack is a much stronger engine.
 

pmramsey

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There are three military versions of the Mack ENDT-673 engine each one progressively better in performance. The last version was usually coupled with the Spicer 5-speed overdrive transmission for best performance. The parts are not difficult to locate except for the unique water pump used by the military and those can still be found at reasonable prices. The Mack comes with a turbo.
 

fasttruck

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Mack ENDTt 673 weighs less than a NH250 and are easier to start in cold weather. You didn't say what chassis you have but my experience in the service was that a M52A1 with an overdrive transmission would run faster than a M818 with a NH250 and out pull a M52A2 with a Continental.
 

sandcobra164

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I am simply contemplating. I use my trucks for work and play and have a line on a M54A1 with the ENDT 673. It is a very stout truck but I want to gauge whether it can handle the same tasks as an M923A0 with the old nifty 250 in it. It would be classified as an M923A1 due to the addition of 14R20 singles currently. Heaviest I have pulled crossed the line at around 24,000 pounds and I rolled around 65 mph for most of that trip. No discussion of manual vs. auto, I have no trouble shifting gears. When I need a truck to do a job, I need the best tool for the job but I do love the sound of a Mack! I am not very concerned about top speed but I want confirmation that a Mack ENDT 673 can be turned up to act in place of a Cummins. 11 liters turbocharged should do the work on 14 liters breathing without forced air.
 

simp5782

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Joseph you see what I do with mine and it is pretty reliable. Just the hole we have on hills is an issue. Any truck is going to have it though. I even thought about swapping in the CAT7155 tranny to get rid of that hole with no turbo. I wouldn't go Mack by no means and if I had a choice to do a $2000 engine upgrade I would go over to a DT466, lighter with a turbo and unlimited resources for more power.

Stick with what you got and use the tips and tricks to get that little bit more power out of her.
 

Csm Davis

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Think I might disagree with Simp5782 mainly because of the manual transmission I feel that gives the Mack the edge for work.

sent from my decrepit fingers
 

simp5782

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Think I might disagree with Simp5782 mainly because of the manual transmission I feel that gives the Mack the edge for work.

sent from my decrepit fingers
Always trying to disagree with me! Just like the ex wife!

Sent from my SM-G860P using Tapatalk
 

AMGeneral

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Ok, I'm gonna throw my 2 cents in here,

Having owned,driven,and worked both over long and short distances,hands down the Mack kicks the 250s posterior in every way but 1,top speed.

The 800 series trucks will manage 56 mph,the M39s with the Mack will top out at 52,I cannot explain why,same gear ratio,same trans,same governed RPM.

The Mack really shows it's power in hard pulls,usually up that LOOOOOOOONG hill whilst towing another truck(or loaded),probably due to it being turbocharged.

The 250 CAN be made into a better runner(turbo,button change,more fuel) but you can do the same with the Mack by turning 2 screws in the IP.

The Mack parts are more expensive,that's true, but run 30 WT oil with a high Zinc content and keep an eye on your valve lash and it will last forever.

As far as filters.belts,etc. The Mack has 2 oil and 2 fuel filters,plus 2 belts.

The Cummins has 1 oil,1 Fuel and 5 belts,so kind of a trade off there.

As to the in cab noise,the Mack wins hands down, none of that normally aspirated rattle.

The Macks have their followers,as do the 250s, but every time I had a choice which truck I drove,it was an M39 with a Mack!
 

acesneights1

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As an owner of both, most of what's posted here is true but one thing not discussed. The radiators in the M39 series Mack powered are hack jobs and not nearly big enough. If you are just gonna use it for a toy, it's fine. Plan on working it hard, expect overheating problems and good luck finding a new radiator if you ever need one and you better have a lot of money. I love driving mine, it's a blast and blows away the multi fuel LDS but I'd take a 250 anyway of the week.
also ENDT 673 is a dry liner engine. Good luck if you ever need to replace one or do an in frame. They are a MF to get out and you will probably find cracks under it.
also the parts guys at Mack(around here anyway) are *******s and won't even talk to you unless you have a serial number from a Mack truck. I was lucky enough to grab a serial number off an old 70's R model with a 673.
a friggin t stat from Mack is 125$...
 
Last edited:

pmramsey

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Ah, The Radiator issue. Many of the military Macks on the road today do not have the original Mack radiator. They have the radiator used on the multi-fuel engines; the difference being the inlet and outlet hoses on the multi-fuel engine radiators must be reversed to accommodate the Mack engine. Call an equipment company in Memphis and they will go to the shelf and pull a multi-fuel engine radiator, send it out to a local shop to change the hose outlets, add $300 to the price of the radiator, and one gets a good reliable radiator for your Mack ENDT-673 engine. However, run it hard under load in weather like this week and operating temps can make one pucker a bit. Not many of us push our Macks super hard so the Memphis solution works great. If you avoid automotive type coolants, watch your coolant Ph., put the heat on your engine slowly, and take the heat away even more so, (no more than 3 degrees a second coming down, it has a turbo you know...don't ask), your radiator and engine will last and last.

I am 90% finished with a cab off restoration of my M54A1 built in 1965 that went through a depot rebuild in 1975. It came from the Army with the upgraded 809-series overdrive transmission, steering, and automatic engaging front axle. I found the correct Mack radiator in original and properly stored crates. I purchased two. (No I will not sell one.) The seller said he'd not had anyone call for one in over 15-years. I paid $595 each. The weight of the metal, finishing, and construction detail are just right for the job.

I enjoy my M818 with only 2700 miles since a depot rebuild. I have put all but a hundred miles on it since 2010. However, I would trade it in a heartbeat for a reasonable M52A1 Mack tractor any day.


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pjwest03

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We have coaxed gobs of power out of 11 liter Mack blocks. This one started as an E6-300 which is nearly the same casting. Mack didn't change much at all over time. The biggest change was the 4 valve heads and electronic econo-vance (junk) of the later ones. 115lbs of boost, methanol injection, propane, laser cut injectors, and a very built injection pump.

https://youtu.be/e_da8IzmxBM
 
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