The Mack Trucks of Jones Transport

I have three Mack trucks with V8 Mack engines and they are a good engine also, but can be delicate under a heavy foot. Don't have that problem myself, but my trucks are not working units.   

Through the 1970's Mack analogy for their engines:

EN  = Engine

D    = Diesel

T     = Turbocharged

After April 1, 1980 the nomenclature was changed to comply with emmisions standards of the time. 

I have three ENDT-866B engines: Turbocharged V8 Mack engines with "Dynatard" engine brake. Also one ENDT-865B engine with "Dynatard" engine brake. Also a spare ENDT-865 without engine brake. All run very well and are not oil burners but have had good maintenance. All displace 866 cubic inches. 

"Maxidyne" tuning did prefer the low rpm lugging and this was very true with the inline six engines; so much so several would split the block through the main webs from the twist. This was corrected through thicker castings in the breakage prone areas. Every time I seen this was in a dump truck chassis. Of these, usually the ENDT-675 series engine which was commonly referred to as the "237" Mack engine, suffered this in the early days.  

The 866 series was rated at 375hp, the 865 engine being rated at 325. The 865 was "Maxidyne" tuning and usually had either a five, or six speed transmission. The 866 series engine had a nine, 10, or 13speed transmission behind it with conventional torque rise. 

I thought them one of the easiest heavy diesels to work on and maintain. Once you mastered how to run the overhead and governor on these, (with correct tools) they were very reliable. Clean fuel filters were a must as a stuck fuel injector would usually disallow the engine to start, or run away as they all worked together. The V-92 engines had a "breakaway" setup that allowed the other fuel injectors to work if one was stuck but the engine ran with a miss. Never seen a 92 series run away myself, but have the 53, and 71 series. 

DMiller is correct in the early V92 engines were not very good. When the "Silver" series debuted, there were vast improvements and GM gave a pretty good warranty on them for the time. The "TA" series of the 92 series was a pretty good engine overall. The "T" was for turbocharging, the "A" was for aftercooling which was water to air. Air to air aftercooling, or intercooling was gaining traction at the time but wasn't commonplace yet.

Never seen a 555 Cummins in an onroad application but a lot in articulated loaders and off road medium sized trucks in the mines. From memory, not a reliable engine and IIRC english built, vendored by Cummins. The 903 series was a decent flatland truck engine, and excelled in boats and watercraft where ample cooling water was available. Heat seemed to be the enemy to both of those engines as they were hard on valves, and head castings.   

The bad thing with those engines of any type running backwards is the oil pump is not lubricating anything. They did seem to want to start easy in either direction. I have a 6V-92TA in a 79 IH 4270 that has been in my family since new. It runs very well but the truck around it is beyond worn out. Easy starter when warm and does a good job as a "yard horse" for me. It starts cold but needs a "sniff" to get going under about 30 degrees. It was my uncle's lowboy tractor for a lot of years and always had good service. It was one of the "Fuel Squeezer" governor setups which was about a joke for pulling power so we did away with that back in 1980 just after the truck was out of warranty. Haven't looked back. We had the truck chassis dynamometer checked once and the engine was apparently right at 345hp and I want to say 1350 foot pounds torque but not very linear. Like most other two strokes it favored 1500-1650rpm minimum to operate at and deliver the best performance. The original RT-9509 Fuller transmission and 4.11 rears are still in it. It has always been reliable. 

I always found the two stroke engines easy to "play" with. Injectors, (fuel rate) and timing were easy to adjust and tailor to usage needs. A lot of the 92 series had more adjustability to the spray pattern than the 71 series had. For instance my 6V-92TA has 9B90 injectors installed. 9A90 injectors worked just a bit better for on highway use than the 9B90. Although the fuel injectors have the same fuel rate, the spray pattern was very different between the two series. The engine torque rise was much better with the seven spray holes of the 9B90 series as opposed to the five spray holes of the 9A90 series. I believe, (my thoughts only) the fuel atomization was better at lower rpm of the 9B90 series and there was less smoke because of this as the fuel was more completely burned. However, the 9A90 series in a line haul scenario seemed to be better with the longer legs and gear ratios of transmissions used on highway. Lot of "Cowboy's" out there that have to have the maximum power to the ground all the time and the 9B90 series worked well for that. Engines, clutches, transmissions, driveline, etc. were worn out faster too citing the heavy foot.

I never was a line mechanic so never worked against a clock, nor had paycheck depend upon how much was accomplished. Therefore had the time to do maintenance and repairs meeting my personal schedule. I like cylinder leakdown tests for measuring internal condition of the engine as a single example. Lot more information gleaned of condition rather than a simple compression test. This is true on any engine. It takes more time to do these tests, but tangible results can be ascertained and tracked. Taking the time to ensure oil leaks are addressed is yet another example.

We all do things differently so I'll not find fault in anybody's work. All you have to do is "Please the Owner" is how I operated on repairing anything. They're happy, I'm happy for the most part. We've all had our share of fuc* up's along the way too, (as I know I have) or wish we'd done something different. However printed literature, proper interpretation of that literature, and an open mind to other's input will take you far is what I've found over the years.