Cummins NT855 serial no. help

Even with a S/N it might not mean much. Who knows what's inside that engine now or if its even original to the truck. A previous owner could have built a Frankenstein engine too.

 

A 270 is considered a 290 just different fuel code. Just like the 250 also had different codes and also rated at 230 and 240 depending on chassis it went in to.

 

The 270 I used for switching and training in the late 70's pulled better than our 290s because the turbo/fuelpump combo was setup for a higher torque at a lower rpm (the torque came on at 1500 for the 270 instead of 1700 for the 290).
I was told the 270 had a bigger air side turbo wheel driven by a smaller (faster) exhaust wheel moving more air at a lower rpm and the pump was calibrated to feed more fuel earlier in the curve while still only pumping enough fuel for 270 /290 hp at 2100.
Our mechanic at the time was a wizard at tuning PT systems and loved the combo and even used a somewhat similar system on the 350 he built for me for heavy haul. Having a long torque curve in a high horse engine (for the day) was excellent when paired with a 5x4 trans and 5.29rears in 55k housings when pulling up to 250k loads on up to 50 wheel combos (2-8-16-16-8).

 

We made a lot of lower power NTC's into 400 + HP. You have no idea what you have anymore. We scribed data for what we had done.
The factory 270 surprised me. RTLO 7 speed overdrive with 5.29 rears . Gauges would read 80 MPH at 2500 RPM but not recommended, I was just along for the ride.
Those 270 BCIII, were torque monsters in their day. They really surprised me.

Ok but just what I remember. 250's were none turbo. Then they jumped to a 290 with a turbo.

 

Yes sir. You are correct. Was just using 250 as another example since it was the only other engine Cummins custom rated lower then advertised so to speak.

 

My 250 non turbo small cam has no cooling nozzles. You cannot build much power on that. The 270 Big Cams I thank had HT3B's and preformed very well with what was out there in the late 80's.