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Doing something with the nhc 250

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M934flatbed

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I was seeing what my options were on the nhc 250, if the oil squirters could be put in for a reasonable price or if I would be better off swapping a civilian 250 or even the 8.3, also is there any suggested brand of pyrometer? I'm going to to use it mainly for hauling loads and some mud play but not much. I have to get my injector pump rebuilt and correct me if I'm wrong, but I want to leave that stock tune? I've read some horror stories on here, she's still running strong but I like to plan ahead :) I'll accept all input, even from the wolfpack
 
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Lukes_deuce

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People have turned up 250s and have turboed them. They are stout motors and are the same block as the 400 big cams. The 250s cannot take the same stresses for long periods of time like a big cam due to missing some internal components, but for hobby and normal use, they will hold up. If your going to rebuild the pump, I would ask them to put a lower number button in than what you have. I think stock button is 27, and the smaller the number, the more fuel the pump will supply. Get a quality pyro gauge, such as Isspro, Autometer or Hewitt and keep it to 1200F or less. I also suggest the dual fuel line mod and some type of air cleaner mod. That should give you a nice little increase in power with out much money into it.

There are other options to add more power, just depends on your budget. You can take parts off another big cam motor and turbo your truck. (cheapest way & easiest) or drop in a good used big cam. I wouldnt put in an 8.3 unless it was free and you wanted to changed the driveline and etc.
 
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M934flatbed

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Lukes_deuce said:
People have turned up 250s and have turboed them. They are stout motors and are the same block as the 400 big cams. The 250s cannot take the same stresses for long periods of time like a big cam due to missing some internal components, but for hobby and normal use, they will hold up. If your going to rebuild the pump, I would ask them to put a lower number button in than what you have. I think stock button is 27, and the smaller the number, the more fuel the pump will supply. Get a quality pyro gauge, such as Isspro, Autometer or Hewitt and keep it to 1200F or less. I also suggest the dual fuel line mod and some type of air cleaner mod. That should give you a nice little increase in power with out much money into it.

There are other options to add more power, just depends on your budget. You can take parts off another big cam motor and turbo your truck. (cheapest way & easiest) or drop in a good used big cam. I wouldnt put in an 8.3 unless it was free and you wanted to changed the driveline and etc.
Click to expand...
Okay, so should I look for a 400 big cam to swap in? I'm new to being around the bigger engines but I've heard the Allison autos are good for 375 as long as you know how to show her some love and not romp on her
 
simp5782

simp5782

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The allisons are junk and do not like high torque or high temps.

Dual fuel line it. #16 button, adjust your rail pressure to around 175. Setup a ram air intake system and leave it be.

It will do fine. You can get up around 300 or so out of just the motor. If you want to add a turbo go for it. It will be fine as long as you are not working it. a 4LHR or HT3B turbo would be fine.

A big cam swap can be more work than most people want to do. It isn't hard but it has some fab work involved. With the allison you wont get the full benefit of the motor. Plus then your transfer case may have an issue.

I have a tuned pump for sale in the classifieds. It is adjusted properly for good power numbers. I ran a NHC250 for 250,000 miles. It can be a beast.

There is a 24v pyro setup on ebay for cheap out of California. I run it on my BCIII i never ran a pyro with turned up pump on the NHC250 as long as you use your head and feel when it is not pulling and just overloading the motor you will be fine.
 
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M934flatbed

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simp5782 said:
The allisons are junk and do not like high torque or high temps.

Dual fuel line it. #16 button, adjust your rail pressure to around 175. Setup a ram air intake system and leave it be.

It will do fine. You can get up around 300 or so out of just the motor. If you want to add a turbo go for it. It will be fine as long as you are not working it. a 4LHR or HT3B turbo would be fine.

A big cam swap can be more work than most people want to do. It isn't hard but it has some fab work involved. With the allison you wont get the full benefit of the motor. Plus then your transfer case may have an issue.

I have a tuned pump for sale in the classifieds. It is adjusted properly for good power numbers. I ran a NHC250 for 250,000 miles. It can be a beast.

There is a 24v pyro setup on ebay for cheap out of California. I run it on my BCIII i never ran a pyro with turned up pump on the NHC250 as long as you use your head and feel when it is not pulling and just overloading the motor you will be fine.
Click to expand...
How much are you asking for the pump? Mine is leaking like a siv and needs some work or replaced
 
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M934flatbed

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simp5782 said:
$450 shipped.. If you want a dual fuel line setup to go with it add $150.
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Yeah, I'll buy that pump and fuel line setup, will I need a turbo or ram air (I assume you mean through the hood bug catcher?) for that setup or will it be cool enough with my head on? And 910-599-1845 is my number, used to live in NC but live in Ohio now, text anytime but you can call during the day however you want to work out the details or just send me a link
 
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Lukes_deuce

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M934flatbed said:
Okay, so should I look for a 400 big cam to swap in? I'm new to being around the bigger engines but I've heard the Allison autos are good for 375 as long as you know how to show her some love and not romp on her
Click to expand...
I havent run enough power through the stock allison to find its limits. My 923a2 has some tweaks and the trans does great, even loaded with 16k to 17k in the bed. I know of a few people who are pushing a lot of power through the allison with lots of mods to the 8.3 with no issues. That guy is also trying to break the trans and has not had any issues yet. He works his truck as well. I know of a 929 with a big cam and stock allison, which gets used and that trans is still surviving. On the other hand, I was looking at a 931 with a big cam and allison. That truck needed a new transmission. Owner said the truck was pulling a loaded trailer out of a field and sheared the bell housing right off the block.

I agree with Simp, that any automatic transmission not designed for a specific torque will not last. For my use, I like the allison. If I was using the truck commercially, then I would of swapped a 10 speed Fuller in.

Last thought, which ever route you go with adding fuel to your motor, please add an EGT gauge. Its cheap insurance and its the best way to tell how your motor is reacting to modifications. It only takes one hot pull and the damage is done.
 
simp5782

simp5782

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Lukes_deuce said:
I havent run enough power through the stock allison to find its limits. My 923a2 has some tweaks and the trans does great, even loaded with 16k to 17k in the bed. I know of a few people who are pushing a lot of power through the allison with lots of mods to the 8.3 with no issues. That guy is also trying to break the trans and has not had any issues yet. He works his truck as well. I know of a 929 with a big cam and stock allison, which gets used and that trans is still surviving. On the other hand, I was looking at a 931 with a big cam and allison. That truck needed a new transmission. Owner said the truck was pulling a loaded trailer out of a field and sheared the bell housing right off the block.

I agree with Simp, that any automatic transmission not designed for a specific torque will not last. For my use, I like the allison. If I was using the truck commercially, then I would of swapped a 10 speed Fuller in.

Last thought, which ever route you go with adding fuel to your motor, please add an EGT gauge. Its cheap insurance and its the best way to tell how your motor is reacting to modifications. It only takes one hot pull and the damage is done.
Click to expand...
The thing that killed my Allisons was heat. Luckily on the A2 trucks they can cool the transmission better with the larger radiator for a smaller displacement motor as well as a Air charged cooler to supplement the heat exchanger. On a NHC250 towing in the summer months the fan clutch will hardly ever shut off.

The sheared off bell housing happened cause he had a u joint in the jackshaft causing a vibration and the bolts backed out and sheared it. Cause I have seen it done even on stock trucks especially dump trucks and tractors that get their frames torqued alot.

The allison wont last a long time behind a working truck with a big cam. period. Least it would't with my setup anyway.
 
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