Old School Engine Discussion - Small Cam Cummins Driveability

I will put in my .02, back in the day, when you took the pump to the shop, you would tell them you wanted a little more fuel, 20% increase was about average and it wouldn't hurt anything. The shop would calibrate the pump for that. Yes, they will change the button and spring, and adjust other things so it would all work together properly. To be honest, this is your best bet. Now, if you really into horsepower, it's a little different ball game. It's doable but with a cost. Goodluck

 

Turn it up and drive easy. Best fuel economy that way.

 

I've got a 1977 White road boss with a power tourqe 270 Cummins 13 speed with 3.58 rears and I put a #10 button and 400 torque spring in the pump. I haul logs with it and usually grossing around 88,000 to 100,000 and it will drag it 80 to 85 mph and it takes a hot b model cat to pass it!

 

I would find someone who really knows what they are doing and have them set it up properly.

I had the pump done on my NTC-350 a couple times back in 1977.
First time was done by "some mechanic" and it ran better than a stock NTC-350, had a .22 button, made black smoke and everything until the pump took a slug of water that scored the throttle shaft and other things.

Second time I take the pump to "The Man" who works at a truck dealership doing nothing but tune ups, setting up pumps and rebuilding injectors all day long and has his own after hours gig doing work for O/O's with their own shops.

I take the truck to him, he replaces the injectors with rebuilds from his own stock, ($25 per, exchange), puts the pump on the bench, goes through the entire pump, sets the rail pressure, makes changes to the throttle shaft, puts in a .32 button and does the top end set up.
Didn't smoke nearly as much, but man did it pull, picked up half a MPG, engine was a lot snappier.

After-cooler started leaking one day, took it to Cummins in Calgary and while I was there I had them dyno the truck.
It was making 350 HP at the rear wheels, in stock form they made around 290 HP if I remember correctly.

 

Back then that 238 was a 238 at the CRANK the 237 was at the wheels....grapes to watermelons comparison