NHC 250 Turbo Conversion in M923

[US6x4]

Doesn't he like to add .120" spacers to run rpms in the danger zone? His engines probably don't last very long.

 

[hethead]

Doesn't he like to add .120" spacers to run rpms in the danger zone? His engines probably don't last very long.

He sure does. His rail pressure must be sky high. He's having a lot of fun though!

 

[Lukes_deuce]

He sure does. His rail pressure must be sky high. He's having a lot of fun though!

This video definitely made my morning! I love me some "Tan buggy" action lol!

 

[hethead]

This video definitely made my morning! I love me some "Tan buggy" action lol!

Tan buggy! That bi#ch is one cheap hot rod!

 

[Superthermal]

Small cams can become 400 magnums. It's a small cam with big cam iii parts.

SIMP, Can you make a bullet list of the modifications you would do (short of drilling oil journals LOL) to a 250 small cam to hop it up.

From what I have seen you post in various threads here:
1. Fuel button, 20 or lower to 16 to get fuel at 200-220 measured not guessing.
2. Dual fuel mod.
3. Pyro for safety for "incompetent" drivers.
4. 1/2" Fuel delivery lines back to the tank pick up.
You also hinted at parts from a BCiii that could be used. What parts would you recommend? Part numbers would be nice but I know your busy.
5. Turbo? You had recommended two different turbos but I cant seem to find that thread tonight to cross reference. What would be the ideal boost pressure range?
6. Inter-cooler
7. Larger Injectors?
8. Specific exhaust manifold?
9. Specific Intake manifold?
10. Swapping the Pump?
After these modifications what would you feel the ballpark HP and Torque output would be around. I am just hoping to be able to spin 16.00s fast enough to clear the lugs of mud. Of coarse I am still eyeing for BC400s.

 

[hethead]

SIMP, Can you make a bullet list of the modifications you would do (short of drilling oil journals LOL) to a 250 small cam to hop it up.

From what I have seen you post in various threads here:
1. Fuel button, 20 or lower to 16 to get fuel at 200-220 measured not guessing.
2. Dual fuel mod.
3. Pyro for safety for "incompetent" drivers.
4. 1/2" Fuel delivery lines back to the tank pick up.
You also hinted at parts from a BCiii that could be used. What parts would you recommend? Part numbers would be nice but I know your busy.
5. Turbo? You had recommended two different turbos but I cant seem to find that thread tonight to cross reference. What would be the ideal boost pressure range?
6. Inter-cooler
7. Larger Injectors?
8. Specific exhaust manifold?
9. Specific Intake manifold?
10. Swapping the Pump?
After these modifications what would you feel the ballpark HP and Torque output would be around. I am just hoping to be able to spin 16.00s fast enough to clear the lugs of mud. Of coarse I am still eyeing for BC400s.

He’s going to answer better than me, but he’s also likely to mention piston coolers, lower compression pistons, and retarded cam timing (to allow for “fuller” injectors that start squirting sooner).

 

[Superthermal]

I pulled all the good stuff (manifold, turbo, aftercooler, etc.) off a big cam 350 about a year and a half ago and put it on my NHC250. I love it. If you are not planning on pulling a 40k# trailer up the Rockies, then all of that talk about piston squirters is a bunch of pointless nonsense. I made mine into a bobber, put 53's on it, and run it like a scalded dog all over the place. I added a boost gauge and pyro. I have never had the exhaust temp get over 700. Make sure it is intercooled or aftercooled. The one piece of advice i would give is replace your main seals. The increase in pressure blew both of mine after a little while.

I had planned on putting a 290 big cam in there, but soon realized that the front motor mount is completely different and would have to be custom fabbed. One day i may do it. Still have the 290 sitting here. If you want to get the fuel to it, do the dual fuel line mod and add an injector pump from a big cam motor, maybe injectors too.
View attachment 677437View attachment 677439

On the parts you pulled from a BC you listed:
1. Manifold, (I am guessing intake? or is this exhaust?)
2. Turbo...? Which one? HT3B?
3. Aftercooler...
4. Dual fuel mod
5. Pyro
6. Boost Gauge
7. Rail Fuel Pressure Gauge
8.?
did you you change the heads? injectors? did you do Jakes? etc... Thanks ahead of time for your reply.

 

[hethead]

On the parts you pulled from a BC you listed:
1. Manifold, (I am guessing intake? or is this exhaust?)
2. Turbo...? Which one? HT3B?
3. Aftercooler...
4. Dual fuel mod
5. Pyro
6. Boost Gauge
7. Rail Fuel Pressure Gauge
8.?
did you you change the heads? injectors? did you do Jakes? etc... Thanks ahead of time for your reply.

If you'd like even more info on the 855's there's a fbook group I found called Cummins 855 enthusiasts. It's exactly that. The 855 was a dominant long haul engine for 50+ years and this group reflects that. Lots of old truckers who've been running 250's, 290's, 350's, etc. turning them up and pulling 40 tons everyday so they've learned a lot and are happy to share. Also some guys who drag race them and do truck pulls at 4,000 rpm with over 120 lbs of boost. Wide range of knowledge.

 

[Superthermal]

Pic from post

Lets See Your 5-Ton!

How well does the M54 blow the 5 Chime? :ditto::?::?: Is that a K-5 or P-5? I want a P-3 (a la Southern Pacific) for mine.

www.steelsoldiers.com

I have a few questions:
1. From this JIMK the owner of this pic has the EGT pyro on the exhaust side of the turbo. Others have it in the exhaust manifold pre-turbo. What are the benefits of either? Which is correct or best practice?
2. From the turbo here is this the Cummins BCIV Exhaust Manifold - 3052859 that is pictured?
3. With the HT3B turbo I am seeing some that have a split intake and others that are single throat... if that is even the description to use... Which is correct for this setup?
4. What size aluminum tubing is this... 4"?

 

[hethead]

Pic from post

Lets See Your 5-Ton!

How well does the M54 blow the 5 Chime? :ditto::?::?: Is that a K-5 or P-5? I want a P-3 (a la Southern Pacific) for mine.

www.steelsoldiers.com

I have a few questions:
1. From this JIMK the owner of this pic has the EGT pyro on the exhaust side of the turbo. Others have it in the exhaust manifold pre-turbo. What are the benefits of either? Which is correct or best practice?
2. From the turbo here is this the Cummins BCIV Exhaust Manifold - 3052859 that is pictured?
3. With the HT3B turbo I am seeing some that have a split intake and others that are single throat... if that is even the description to use... Which is correct for this setup?
4. What size aluminum tubing is this... 4"?
View attachment 879169View attachment 879170

I believe that’s 3” tubing from the compressor to the intake manifold (I was wrong, it’s 3.5”). Pyro’s can be installed before or after exhaust turbine. They read about 200 degrees cooler when they are installed after. They also don’t react quite as quickly so I believe preturbo is the better option. You shouldn’t see over 1100 degrees there. I keep mine under 1000. On the manifold/turbos questions I have no idea.

 

[WillWagner]

Manifold is N14. Turbo also looks to be from N14. HT3B did not have marmon flange compressor outlet. Don't remember model number, it is a divided entry. The turbo/manifold combo above will make things work sooner, small port manifold and turbo, however, the exh ports on N14 were small to increase exh gas velocity, the stock heads on a non rebuilt NHC are big, like twice as big. There are heads with small ports. The two types can be intermixed, small and large port, on the same engine.

 

[Superthermal]

Manifold is N14. Turbo also looks to be from N14. HT3B did not have marmon flange compressor outlet. Don't remember model number, it is a divided entry. The turbo/manifold combo above will make things work sooner, small port manifold and turbo, however, the exh ports on N14 were small to increase exh gas velocity, the stock heads on a non rebuilt NHC are big, like twice as big. There are heads with small ports. The two types can be intermixed, small and large port, on the same engine.

Your comment: "Turbo also looks to be from N14"... Does this N14 turbo have a part #? Or model name? as either would help. From what I understanding from the above comments is the N14 "stock" turbo has a quicker spool when used with the N14 smaller port manifold, which I presume will help with the larger gaps in my M813 5speeds ratios to help get some boost around the 1500 rpm range where the motor drops back to when shifting up through the gears. Is there a preference here for the stock N14 turbo (yet to be named part number/model) vs the HT3B? If I was to use the N14 exhaust small port manifold will it work with an HT3B turbo as well?
Thanks for helping the blind, dumb and deaf get their turbo setup list correct...

 

[simp5782]

You need a Big Cam exhaust manifold and a HT3B, 4LHR, T46/ST60, HT60 turbo. If you dont care about the $350 manifold cost then just buy pulse manifold from a diesel distributor.

N14s came with HT60s which is just slightly more flow than an HT3B.

4LHR/T46/60s are 350hp turbos

If you want both I can ship you a manifold and a HT3B turbo

 

[Superthermal]

With exhaust connections It appears these sections are 5" and are a "standard" off the shelf S sweep and 90 degree sweep. This is a muffler delete. Any input on how the exhaust side is done here? Is it better to use a flexible section to remove vibration stress from the turbo/exhaust connection?

Lets See Your 5-Ton!

I could be mistaken, but that looks like GL LOADING OPS TRAINING to me. rofl :popcorn:

www.steelsoldiers.com

 

[simp5782]

With exhaust connections It appears these sections are 5" and are a "standard" off the shelf S sweep and 90 degree sweep. This is a muffler delete. Any input on how the exhaust side is done here? Is it better to use a flexible section to remove vibration stress from the turbo/exhaust connection?

Lets See Your 5-Ton!

I could be mistaken, but that looks like GL LOADING OPS TRAINING to me. rofl :popcorn:

www.steelsoldiers.com

View attachment 879230View attachment 879231

That is a pulse exhaust manifold so it's gonna sit higher than a standard big cam one.

Looks like it just ducks out thru the same fenderwell hole

 

[US6x4]

Yes, it's best to have a flex section but it's very difficult to find the room to add it in.

FYI, the compressor tubing on my bht3b turbo is 3.5"

 

[Superthermal]

You need a Big Cam exhaust manifold and a HT3B, 4LHR, T46/ST60, HT60 turbo. If you dont care about the $350 manifold cost then just buy pulse manifold from a diesel distributor.

N14s came with HT60s which is just slightly more flow than an HT3B.

4LHR/T46/60s are 350hp turbos

If you want both I can ship you a manifold and a HT3B turbo

If you want to send me a PM with a price on what you want I will start counting my pennies..