NHC 250 safe power Mods.

[290smallcam]

Some tips for those who are adding a turbo to the NHC 250, and some need to know info. When adding a turbo to a NHC 250, you need to do 3 things. 1. Retard the timing. Stock timing is (0.2032) piston and (0.0290) push tube. Set it to (0.2032) and (0.036). This timing is for a stock NTC 290 S.C.. 2. Order a Cummins 855 S.C. camshaft part # 3023229 or 3023177. This is the 290 SC camshaft. The NHC 250 will not accept big cam camshafts. 3. compression ratio on NHC 250 has a ratio of 15.8:1. That's not real bad, if you tow or hot rod a lot you ll burn a hole in a piston. If you just drive normal you will be fine. If not order piston set for a 290 SC part # AR-08190 or 203090. The NHC 250 does not have piston coolers, so you will not be able to run it hard. They did make small cams in the 400HP range though. You can step up to 290-300 injectors only if you turn up ur fuel pressure. you add more stress on the camshaft when you turn up the rail pressure. Switch to a #15 or 17 plunger/fuel button. Research done by pittsburg power has shown that adding a dual fuel line will add 25HP and lower EGT by 100 degrees. You can go all out, but these are the cheap ways and make your NHC 250 live longer. So really you are building an 290 SC, but with more power if you change injectors, button and fuel pressure. If I remember the cam was around $300, pistons $490. Cheaper than buying a used 290 or 400 BC. Its like I have a 350 in my 5 ton now. What ive notice the most is power. itll move them 53 XZL tires. run smoother. was going to swap the 5 speed out but it dosent lag or bog anymore! Turbo boost should be 15-18 psi, any more is to high. If boost is more turn down ur furl pressure or check ur plunger/button size. Stock boost is 290/300 @ 15-18 psi. 350 is 18-24 psi. and 400 is 25-28 psi. Im sure you can get 400HP out of the NHC 250, but really! Why? If you need info let me know. add pryo too!!!!

 

[simp5782]

I would really like the specs that cummins did to make the NHC250 into the small cam 400 magnum. That is how you make something of that motor then.

 

[290smallcam]

I don't know. I seen a post somewhere that they made the smallcams up to a 400HP.

 

[simp5782]

I don't know. I seen a post somewhere that they made the smallcams up to a 400HP.

They did recon motors of small cams and turned them into big cams. Called em 400 magnums. They have stamped stainless steel valve covers and cross pipes to identify

 

[290smallcam]

Isnt the cam bore on a SC smaller? a big cam camshaft wont slide into a SC?

 

[290smallcam]

If I remember right, high power SC suffered short lived cams because there was to much pressure on the lobs.

 

[Crf450x]

I really try not to argue with people on here but adding a turbo is not even close to that complicated. Will the stock cam and timing be OPTIMAL? Probably not. But they surely won’t hurt anything. And I’d legitimately love to see evidence of the dual fuel line deal adding any measurable power because the logic simply isn’t there without more injector flow. Definitely not gonna add 10%. And even if it did (it doesn’t), how would adding fuel lower egt? Also, burning a hole in a piston is from heat or, in extreme situations, way too advanced timing combined with high heat. The lack of oil squirters will never be a problem until the egts get too hot. A turbo is very beneficial in regards to that.

That being said, if you want to do all the things listed, it won’t hurt a thing and will likely be better, but not noticeably so.

I hope I didn’t sound like an ass....that wasn’t my intention.

 

[290smallcam]

Pittsburg Power on their site has a book wrote by Bruce. It covers the cummins NTC. 104 pages!! His claims is proof I guess. He states 100 degrees cooler EGT with 25 more horse. Its called ..Have to re check. post latter.

 

[290smallcam]

google this... Diesel Injection of Pittsburgh Presents: How To Build A High-Performance Diesel Engine... A really good read. Full of facts and proof.

 

[Floridianson]

Pittsburg Power on their site has a book wrote by Bruce. It covers the cummins NTC. 104 pages!! His claims is proof I guess. He states 100 degrees cooler EGT with 25 more horse. Its called ..Have to re check. post latter.

I am by no means expert on getting big HP gains from the Cummins. I would believe 25 HP gains from duel fuel if all the other mods have been done and much bigger injectors. Got to feed those hungry puppy's at high RPM. looking at the Cummins 250 injectors with it's metering orifice and the small inlet orifice they can only flow so much even with a little higher rail pressure. You are not going to double the fuel inside by any means to the injectors. Will just adding a turbo add something sure would seem like it by raising compression but as said we still need more fuel on the top end plus other things to take advantage of it. To me to make real power we need to do some other mods. and for me that would have been to much work / money when I had the 250.

 

[Crf450x]

google this... Diesel Injection of Pittsburgh Presents: How To Build A High-Performance Diesel Engine... A really good read. Full of facts and proof.

Thanks for posting that! That’s a lot of reading. I’ll try to get through it this evening. Just remember those guys are in the business of selling parts/service.

 

[WillWagner]

400 Magnum was a short lived, cam eating shi t box. Early in the Cummins evolution of STC, Step Timing Control, they didn't have enough real world testing to see how the longevity of the engines would be effected by the increased cam/follower pressures. The BCIV's that were STC had a rash of cam failures that was later determined to be due to the oil feed cross drillings in the follower shafts being on the same plane as the force on the shafts created by the increased injection pressures. The pressures weren't from higher FUEL injection pressures, but from the oil fed hydraulic tappets...similar to GM valve tappets but with a bleed off valve incorporated. I was directly involved in the field diagnosis, testing of these engines after the inherent failures were popping up. Cummins Stopped field testing just prior to the BCIV development/release as a cost cutting measure. As time went on, LATE BCIV, New BCIV and early N14 engines, STC was a good system on low HP engines, up to<IIRC 410 HP. After that, again cam eaters.

STC engines were 365 to 444/450 HP. 444s were the first black....well, Bluke colored engine Cummins did. Bluke was a mix of black and blue, hence Bluke

The Magnun 400 was a Diesel ReCon engine. A Cummins subsidiary, with Cummins backing, but NOT CECo. They were black

And, no cam change on SC290's to go from non turbo to turbo, Timing, well, .006 on the positive end of injection will not be noticed.

 

[WillWagner]

They did recon motors of small cams and turned them into big cams. Called em 400 magnums. They have stamped stainless steel valve covers and cross pipes to identify

No, not true, Blocks are totally different. Absolutely NO way to do that.

 

[simp5782]

No, not true, Blocks are totally different. Absolutely NO way to do that.

Sorry will put CPL 695 is a small cam with big cam iii parts thru recon. Magnum being the designator as recon. Common thing in Australia apparently back in the day. It's still a small cam I guess in idea but its got all the other guts of a big cam and 400hp

 

[290smallcam]

so lets say I want to swap to a Big Cam? Which one will give me the best power and give me the MPG I want?

 

[Crf450x]

so lets say I want to swap to a Big Cam? Which one will give me the best power and give me the MPG I want?

A big cam has more power potential because of the ability to use higher fuel pressure. People have put them in 5 tons.


But you were just saying how happy you are with how it runs.......?

Cheaper than buying a used 290 or 400 BC. Its like I have a 350 in my 5 ton now. What ive notice the most is power. itll move them 53 XZL tires. run smoother. was going to swap the 5 speed out but it dosent lag or bog anymore! Im sure you can get 400HP out of the NHC 250, but really! Why?

 

[290smallcam]

Yea, but mybe someone knows of something better. I posted a tread about buying a M35 and putting in a Cat 3126B so I would have something with better MPG. Wont be doing that again!! WOW, started something bad! So ill just keep my 5 ton. Guess I could do a Cummins M 11 or Cat 3176B/ C-10 if fuel gets to $5 a gallon.

 

[simp5782]

Big cam is the smarter swap. Easily done in a day or so. Plus you have Jake's unlike the mid range cat motors that don't.

Allison 654 won't last long being hard or abused. Not many sae 2 auto transmissions that will take the power so you will have to see a manual install or sae1 automatic like an ht740 or 754. You will have to raise the cab. Make new engine and cab mount brackets. Move transfer case and driveline. Ect.

 

[Crf450x]

Yea, but mybe someone knows of something better. I posted a tread about buying a M35 and putting in a Cat 3126B so I would have something with better MPG. Wont be doing that again!! WOW, started something bad! So ill just keep my 5 ton. Guess I could do a Cummins M 11 or Cat 3176B/ C-10 if fuel gets to $5 a gallon.

With enough money and time, anything can be done. If you want to swap, a big cam or n14 would be cool. Personally I am 110% happy with how mine runs with the turbo and a little more fuel.

If fuel gets that high I’ll be looking for a smaller toy.....

 

[WillWagner]

Later production SC engines had things like suitcase WP, FFC lube systems, swept manifolds instead of the log type. Still had 5 -7 gallon pans and external suction tubes made of woven hose. The progression of those engines was just that, progression to fix the short comings and to simplify maintenance and costs. Here in the States, the ReCon Magnum was an STC engine with all of the above BC style parts with the addition of Step Timing to make it meet emissions for the years it was made, it was not a re man, it was a new and different engine so it could not be made to the old small cam emissions, it needed to meet the current in place emissions for new engines. Yes, it was a ReCon manufacturered engine, but was a new platform that when released, needed to meet the, IIRC, 1986 or 7 emissions. Don't know about the Aus engines except that long about the same emissions stds were adopted by Aus. Down under did have more HP available to them.