Cummins NHC 250 vs Mack ENDT 673

Steel Soldiers is supported by:

pmramsey

Member
391
10
16
:jumpin:OMG...That is one sweet looking B Model Mack. I just love those old 50s and 60s Macks!:-D
 

pmramsey

Member
391
10
16
This is my last contribution as to why I prefer the Mack ENDT-673 5-ton over the Cummins NHC 250.
I have a 40-mile course over which I like to run a truck through its paces. It starts at Massie’s Corner at the intersection of US 522 and US211, runs through Sperryville on 211 up and over Thornton’s Gap (2,460 ft.) down into the Shenandoah Valley and turns north on US 340 following the south fork of the Shenandoah River to Front Royal. This connects back to US 522 and goes up and over Chester Gap through Flint Hill and back to Massie’s Corner. These are all 1950s type two-lane roads with posted speed limits of 45-mph for trucks and 55 mph for autos.
The route out of Sperryville is 6 miles to Thornton’s Gap and a climb of 1,100 feet that includes three switch backs nearing the top. This is not what one would exactly call a very high elevation.
Yesterday, the afternoon temp at Thornton’s Gap was 99F with a dew point of 74F and barometric pressure of 29.90. This meant the density elevation at which an engine would have to produce its power was 5,908 feet.
As with many non-turbo engines, the NHC 250 is incapable of producing more than 75% power above 5,500 feet and even that number is dependent upon proper fuel leaning which the military version of the engine does not offer. The power available yesterday going up to the gap would have been 73% of its max rated 240hp or 175.2hp. Without leaning, the estimated power output would be in the 68-70% range or 163-168hp.
On the other hand, the turbo Mack ENDT-673 maintains its full power output of 210 or 220hp (the last version of the engine installed in the 1970s rebuilds were 220) to over 10,000 feet. Yes, the Mack will run hot under these conditions as the turbo intake temperate can push 1500F under such conditions. An inner cooler and fuel leaning would have been nice additions.
The answer to the Mack vs NHC 250 is best answered with another question. Given that both trucks are very close in weight and if you are using your truck for more than recreational use, which truck would you have preferred to take over Thornton’s Gap yesterday; one with 163-168hp or one with 210-220hp?
There was a time when the Marines out of Pendleton would take an occasional convoy exercise going up to Big Bear Lake. If the weather was against them, it was not uncommon to observe an M35A2 blowing its guts out the stack and its M105 trailer slowly doing a jackknife. The Lake is 6,700 feet and density altitude can easily reach over 12,000 feet. Just hope the dry Santa Anna winds are blowing.
 

msgjd

New member
56
0
0
fasttruck posted: "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."


I concur with "fasttruck", plus the Macks seemed more responsive on hills than the m809-series. The last unit I was in would install macks in their A2-model trucks whenever a multifuel engine failed, and somehow got away with it in the paperwork. During my time in, we had all four 1950's-1970's versions of 5-tons in the motor pools. (gas/mack/multifuel/cummins) . We rarely could get an M809-series to start below 28 degrees. And if you got caught with ether you got in big trouble with Maint. By the time the (12V! wtf) preheater did its job there never seemed to be enough juice left to whip that motor fast enough. The first winter we learned quick to walk right by any M809-series and go to the gas 5-tons first. If none were available, it was off to find a mack next. Or, egads, an A2. To us, multifuels were undesirable unless they were in a deuce.

But it is true that any 855 cummins is easy to work on, and cummins 855 parts are easy on the wallet. I would only go to an ENDT673 to re-motor an A2 (multifuel). If there was an A1 and an A2 of the same model I wanted, i would buy the A1 hands-down. But I admit I have always had a soft spot for the gas 5-tons when they are set up right and have the (2910-00-562-0441) mil-upgrade zenith carburator . (not the coughing holley)
 
Last edited:

snowtrac nome

New member
1,569
2
0
The one advantage to Mack engines were the wide torque band, this is why mack was able to use 4 speed gear boxes long after every one else had gone to road rangers. with the military 5 speed this is likely why the mack had a better seat of the pants feel. One day I would like a mack powered wrecker, but its not in my budget right now.
 

msgjd

New member
56
0
0
I know what you mean exactly. Macks were always excellent luggers. I've hauled overweight-interstate part time for the last 30+ years. Even when the "new" CH-models arrived, you grabbed a gear, and like their predecessors they would drop below 1400 and just hover there no matter what. I haven't been in any post-1990's mack, don't know if the legend continues.

On the opposite side of the scale, it's been said lugging an 855 cummins does damage long before over-speeding will. I won't let any of my 855's drop below 1700 on a hard grade.

I would like to re-motor my M62(A2) back to gas if I had another spare engine, but with the price of non-ethanol gasoline (plus I make biodiesel) , I'm actually looking for a late-model 673 for the wrecker. Bad side is I don't have any spare parts for 673's. I have trailers full of crap for the others. I really should be thinking about selling out and fully retiring instead of adding to the incomplete life-long project list. :cookoo:
 
Last edited:

pmramsey

Member
391
10
16
B & B Military Surplus at Altona, NY there near where you live has supplied me with parts for my M54A1 for a long time. I purchased two Military water pumps and two Mack radiators from him as they are the two most difficult items to find for the ENDT-673.
 

msgjd

New member
56
0
0
m125 which might no longer exist at moore's

I have heard of B&B up there but they are a bit of a ride even for my location. About 40 miles south of them in Keeseville is George Moore's. About 10yrs ago someone on here posted "If you have a high tolerance for crotchety old men..." :roll: Well 'ol george and I butted heads for decades. You might've paid a fair price for parts and trucks if you caught him on a really rare day. He also had a bad habit of outbidding me at the DRMO sales locations in northern NY/VT. He could afford it #1,, and #2, he lived about 65 miles closer to the DRMO's. The last time I saw him alive was in 2008 I think when his grandkids were taking over. Good reasonable kids. But 'ol george true to form came out and overruled the deal, upped the price. The grandkids were very apologetic about their grandpa. I hear the grandkids still are much better to deal with, but they may have scrapped all the pre-1980's stuff by now. They have a bunch of newer stuff these days. Don't know what happened to the M125 that was there.


M125 keeseville.jpg as seen there in 2008

And he did have several A1-Macks and 673 motors & parts once upon a time. I bet his grandkids know they will be a long time undoing the previous reputation. Well, he did make some huge donations to good causes.

To george, may we butt heads again in the sky
:papabear::swbradley1: are you gonna sell me those trucks and parts, or not???


(which reminds me of another who must've been related, Harold Gilmore's sales & yard in Bomoseen Vt. As late as the 1980's you could still get M135 and M211-etc trucks & parts by the boatload. That's IF he would part with them. One day he wanted $2800 for a nice clean M215 dump. When I inquired again a week later, it was gone, at $1700)

To harold, I fear I've become very much like you with my "stuff"
 
Last edited:

Ajax MD

Member
532
1
18
B & B Military Surplus at Altona, NY there near where you live has supplied me with parts for my M54A1 for a long time. I purchased two Military water pumps and two Mack radiators from him as they are the two most difficult items to find for the ENDT-673.
Unfortunately, the owners retired and shut down just recently. They sold their stock to another vendor but I'm not sure who.
 

msgjd

New member
56
0
0
My 1st guess would be Tennis Industries. John bought out a good deal of stuff from george mainieri (RIP pal) at Vt Commercial Salvage several years ago now. But again, it's only my guess and I've been wrong many a time. Not starting any rumors here :whistle:
 

fasttruck

New member
818
1
0
Reference post 17: If you bring them the serial number for the engine they (the dealers) should be able to furnish parts. Same with transmissions and rears. If you bring the serial number for the truck and that serial number does not match the components in your truck there could be problems. I bought an expensive input shaft once for A TRT 722 only to discover when it was in the truck that a chassis with a Mack Clutch requires a different shaft than a truck with a Spicer. Transmission I got the number off was on the ground. Fortunately an old time parts man remembered selling a few chassis with Mack double disk clutches and 722 series transmissions and armed with that info I got the correct part.
 
Top