Big Cam Cummins reliability

You should rephrase it they are the best if you can do all your own work on the engine. Its getting harder and harder to find people to make the old ones run right. Half the new mechanics won't even know how to properly diagnose a problem because he won't have a computer to plug into

 

Bought my first truck,69 CO4070A,in 1974. Had a NTC 335,13 speed direct. Great engine,turned it up,would pull with anything on the road at the time. But,it does effect the longevity of the engine overhauls,and hard on fuel. But fuel was .30 so who cared.
Sold it,and bought a new 4300 Eagle in 1977,NTC 350,13 speed. Great engine,ran it till 1985,pulled the engine,trans,and put it in a new glider,ran that same engine till 1996. Inframed it several times in the 19 years I owned it,crankshaft never out of the block. Inframe cost was less than two thousand dollars,unless I needed counterbore work. Do it in my shop over the weekend,fresh engine ready to go on Monday morning. Finally sold that truck and engine,and bought a 95 9300 Eagle,N-14 500 redhead,cpl 1844,15 speed. Ran it 21 years till I retired,engine never had the head off. By far the best engine I ever owned.I've hauled specialized,oversize my whole life,so I don't crank the mileage widget haulers do,but my trucks worked hard,I maintained then religiously.
Cummins worked great for me in my career,very low cost of ownership,simplicity,parts availability,and the old N engines will just flatazz work. Everyone will have a favorite,but fwiw my 42+ years of Cummins N-series ownership,certainly helped me into my happy retirement. Still have an old Dodge Cummins dually,will never get rid of it.
My 9300 Eagle

 

I run a Big Cam every week....

How you take care of an engine determines how it takes care of you, especially these mechanical engines.
Don't lug it way down, and if you have a big fire built in it keep an eye on the Pyro!!

Big Cam & B model Cats both good engines. I started with Cummins back in the 80's and tend to still use them.
They require a tune up just as the old 2 stroke Detroits did, sadly many never got it and when they gave poor performance.... they were considered bad engines. Yes I have experienced this in fellow drivers!!

What CPL # is the engine you are looking at?
I ran around 78,000 and 79,000 lbs all this week and averaged 5.2 mpg. Considering it's a dinasour to most, it's still reliable if you take good care of it.

 

My dad had a bc4 cpl 838 with some fuel going to her about every 350-400k she was due for an inflame. Not a complete overhaul pistons liners rods&mains

The old mack e6 and early e7 vmac 1-2 with the p pumps were true million mile motors. Hard to kill with just a little bit of preventative maintenance. Not power houses by any means but they'll show up and get r done everyday

 

Old big cams are good. Easy to maintain,like everything else tho do proper maintaince an will run forever.worked on many of them, of corse im partial to them.

 

I've pulled 100k with my 400 with no issues. Make sure you get something that is geared correctly for what you will be doing

 

What’s the determining factor to help figure that issue out? Is it more about the weight and hills or are we strictly talking fuel Mileage? This wording gets thrown around a lot, just curious if it’s written in stone somewhere? Truck spec manuals or just plain experience advice?