NT and NH parts interchangeability

[ke5eua]

I am looking at getting a new PT pump and can't help but notice if it is labeled military the price automatically jumps up a couple hundred. My question is are the PT pumps interchangeable between the small cam and big cams? I came across one that lists it fits both NT and NH engines but I also came across a thread that said nothing is interchangeable. I'm lost here, and I just can't see spending upwards of 600 for a pump just because it is painted green and has a nsn attached to it when I can pay 350 plus shipping for a cummins pt pump brand new.

I plan on rebuilding my current one and having it as a spare or selling it, not sure. Just want to put a new one in it for now.

 

[doghead]

I have to ask, since you read both answers(yes and no) on the Internet, how can another answer here(on SS) make you sure of anything.

 

[ke5eua]

I have to ask, since you read both answers(yes and no) on the Internet, how can another answer here(on SS) make you sure of anything.

Possibility that someone has first hand experience with it.

Comparing the two pump the mounting flanges are identical, fuel in, out, and return are identical. I just don't want to get something and end up being wrong.

Like I said, one seller said it fits both nt and nh 855 engines, but a thread from a couple years ago one person said the only thing the two engines share is the 855 classification.

If this was a turbine engine I wouldn't have to ask, but when I get conflicting info I have to ask the masses and hope someone has done it or knows it can be done with no ill effects.

 

[doghead]

The only person I would trust to know this for fact is Willwager.

 

[wcuhillbilly]

Im going through the same debacle myself as I have a 250 Nat Aspir in my 816 and a locked up core (parts-turbo/jakes/heads) NTC 350 laying next to it... Cummins keeps saying that they are the same with the caviot that the fuel buttons are differant...... well buttons can be changed.... I would like a straight answer too but the pretty lady at the parts counter at Cummins says she isnt sure, and most of the Techs in the back get a glazed look when I mention an 855,,,, there reply is "thats really old" I dont know,,, Isnt that similar to the early N14"?
So Im leaning to the side of the fence that yes they are the same, with the exception of the fuel button. If your in that deep, do the duel fuel mod... old truckers and loggers swear by it..

 

[WillWagner]

If you are asking if it will fit, yes it will. If it will work, maybe, enough to get you off the road. The biggest difference between a pump for the NHC and NTC is no turbo. The NTC pump has what is called an AFC, Air Fuel Control. This part is needed to let the pump make fuel pressure. As the manifold pressure increases, the AFC plunger is pushed toward the inside of the pump and allows the pump to increase pressure by uncovering holes in the AFC barrel. It is kind of a catch 22, gotta have manifold pressure to get fuel and gotta have fuel to get manifold pressure. The right balance results in a smooth but snappy acceleration with light smoke. MOST pump shops just throw things together to get the right rail pressure but the result is black smoke...wasted diesel gas...on acceleration. The NHC has a plugged AFC cavity and just makes the needed rail pressure by way of the governor part of the pump. If you use an AFC pump on a non turboed engine, the only rail pressure the engine will make is what is called no air fuel. It is usually around 45 to 70 psi. The rail pressure you need in your NHC is prolly around 125-150. The reason you only get the 45-70 psi is that there is no turbo to push on the AFC plunger and uncover the holes in the barrel.

As for hard parts, like heads, rods, cranks, yes, they will work, but, there are "performance parts" like pistons, cam, injectors that are CPL specific and timing, both the initial timing with the cam key and the cam follower shims are different from CPL to CPL.

 

[Suprman]

I sold a pump set for the cummins 400 to a guy with an 855. He put it on and said it was higher pressure and that would give him more power. He is planning on upgrading to injectors from a 400. But I don't know if there are different 855 engines and if so which one he has.

 

[ke5eua]

If you are asking if it will fit, yes it will. If it will work, maybe, enough to get you off the road. The biggest difference between a pump for the NHC and NTC is no turbo. The NTC pump has what is called an AFC, Air Fuel Control. This part is needed to let the pump make fuel pressure. As the manifold pressure increases, the AFC plunger is pushed toward the inside of the pump and allows the pump to increase pressure by uncovering holes in the AFC barrel. It is kind of a catch 22, gotta have manifold pressure to get fuel and gotta have fuel to get manifold pressure. The right balance results in a smooth but snappy acceleration with light smoke. MOST pump shops just throw things together to get the right rail pressure but the result is black smoke...wasted diesel gas...on acceleration. The NHC has a plugged AFC cavity and just makes the needed rail pressure by way of the governor part of the pump. If you use an AFC pump on a non turboed engine, the only rail pressure the engine will make is what is called no air fuel. It is usually around 45 to 70 psi. The rail pressure you need in your NHC is prolly around 125-150. The reason you only get the 45-70 psi is that there is no turbo to push on the AFC plunger and uncover the holes in the barrel.

As for hard parts, like heads, rods, cranks, yes, they will work, but, there are "performance parts" like pistons, cam, injectors that are CPL specific and timing, both the initial timing with the cam key and the cam follower shims are different from CPL to CPL.

Makes me wonder why the guy on eBay is advertising the pump as it will fit both nhc and ntc 855 engines.

 

[Floridianson]

Makes me wonder why the guy on eBay is advertising the pump as it will fit both nhc and ntc 855 engines.

Bottom line it will fit but the calabration could/will be off.

 

[WillWagner]

Bottom line it will fit but the calabration could/will be off.

^^This. It WILL fit, exact same bolt pattern and dimensions, but it won't work very well.

 

[ke5eua]

Thanks for all the feedback.

Now to just figure out which direction I want to go in.

I'm knowledgeable now and know what I need so I'll look correctly and not blindly just taking a sellers word for it.