Mechanical N14 maximum OE hp

You wanting to build something like this only in a mechanical version… ?



Cummins N14 650-700hp build

 

Need to find out what you have first like camshaft / pistons. Get that ser number to get the Cpl number and build from there. Camshaft may be compatible but the the cam key may not, just a starting point….

 

I have a mechanical N-14 in my truck.
ESN 11657055
Original CPL 1532, 350 hp.
It was overhauled in 2020, I bought it in August 2022, and have put nearly 300,000 miles on it since.
The overhaul kit was p/n 4024878 which is the lower compression, anodized bowl pistons, etc for a 430hp STC mechanical N-14.
No record that the cam was changed, and I have not checked timing on it.
It had 3078198 injectors in it (230 cc) and the pump appeared to be set for the original CPL 1532. #25 button, 150-160 psi fuel pressure, 27-28 psi boost on a hard pull.
I pull primarily flatbed all over KY, TN, IN, VA, NC, with occasionally forays farther out, and sometimes pull a reefer or rgn, but 90% of my work is flatbed.
Pulled pretty decent for what it was, got very respectable fuel mileage.
Fuel mileage for 2023 was 6.185 mpg for the year.
I ended up turning the pump up as far as I could. Throttle shaft screw all the way out, #0 button.
Fuel mileage for 2024 was 6.315 mpg for the year.
June of this year I sent the pump and injectors to Warren at Premco.
The injectors are now 250-255cc’s, and the pump was virtually unchanged. All he did was delete the AFC because the diaphragm was torn and the mechanism seized up.
I put on a new air to air at the same time because the old one had a massive leak.
Now it will hit 33-35 psi boost, 220-230 psi fuel pressure, and I’ve never seen the pyro over 825° post turbo.
Fuel mileage for 3rd quarter 2025 was 6.81 mpg, and for the year so far it is 6.35 mpg.
I really really like STC, and think almost all of its bad reputation comes from poor maintenance. I run a Fleetguard LF9009 primary filter, and Harvard 7502 element in my Luberfiner housing. 15,000 mile oil change intervals, with the 7502 element getting changed at 30,000 miles. I have had zero STC issues.
There are a few things I’d change if I were to build one, but I am very happy with what I have.

 

Picture from today.
Topping the last long hill westbound on the Bluegrass Parkway in KY.
If you’re not familiar with the hill, it’s almost 450’ elevation gain in approximately 2 miles.

 

You are correct. It doesn’t smoke much at all, and starts very easily. Even at 0° with no block heater.
It barely hazes on a shift the way I normally drive. If you gouge it on a shift you can get a cloud out of it, but I just don’t drive like that.
And, I live by the motto, “Load it like a shopping cart, drive it like an old fart.”
68 mph is my happy spot with this ole heap. 1,550 rpm with a 13 speed, 3.36’s and short tires. I come out of the big gear quickly because I like to be 1,700-1,800 rpm when I work it hard.