So who has bumped the power on a 6CTA cummins

[Ecscnvb]

Nope, they are a perfect fit. They will rev to about 3100-3400 in an 8.3L. You’ll want to manually shift the trans when you really need the power, as these will not change the trans shift points. During normal driving, no problem. The 8.3L in marine apps spin up to 3400, but they do use a different harmonic damper. Don’t know that p/n, sorry.

What is the redline on these motors?

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[74M35A2]

Diesels really don’t have such. The stock governor on our mil spec 8.3 pulls out fuel at 2200-2300rpm. If you are asking at what rpm it throws a rod, I’m not sure that is known here, or anywhere besides the tractor pulling group.

 

[Ecscnvb]

Diesels really don’t have such. The stock governor on our mil spec 8.3 pulls out fuel at 2200-2300rpm. If you are asking at what rpm it throws a rod, I’m not sure that is known here, or anywhere besides the tractor pulling group.

3400 is ok?

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[74M35A2]

It is in marine with the appropriate damper. Ask member grendel here. He has a GSK (governor spring kit) in his 8.3 and has wound it up. He also felt abnormal vibration at elevated RPM that the hi spec damper likely absorbs.

I can’t promise your engine will stay together at anything over 2200rpm. Heck, it may not even stay together then. That’s why the military sold these trucks, they are 25 years old.

 

[Ecscnvb]

It is in marine with the appropriate damper. Ask member grendel here. He has a GSK (governor spring kit) in his 8.3 and has wound it up. He also felt abnormal vibration at elevated RPM that the hi spec damper likely absorbs.

I can’t promise your engine will stay together at anything over 2200rpm. Heck, it may not even stay together then. That’s why the military sold these trucks, they are 25 years old.

How do I get in touch with him? I'm new to using this site. Thank you.

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[MAdams]

Can we put 3-4 questions together before posting rather than chat room style?

 

[grendel]

I would not rev the 6CTA in our trucks over 3K. Cummins says they see a lot of snapped crank shafts due to differential harmonics. No damper in the world can manage that. The marine motors mentioned use a different crank.

The 5.9L springs for a 6BT - Bosch P7100 work and they're down rated in our pumps. So a 4k rpm spring is about 2950 in ours. It's what I put into most of the trucks we've built. They're happiest under 2800 rpm - ish... every motor is different. Keep in mind, it's not just springs... it's the entire enchilada that keeps your motor safe and generates power AT HIGHER RPM - without air and fuel mods, I'd stay at stock mil spec 6CTA RPMS.

It's pump timing, fuel loads/injectors, turbo/air, air restriction and then of course, exhaust restriction and valve spring capability. Get a EGT and boost guage before you do fuel/air mods, please.

Most of the trucks we've done use a bigger turbo, different injectors, different pump calibration, different intake with a charge air cooler, stacks and a PAC brake.

 

[Ecscnvb]

I would not rev the 6CTA in our trucks over 3K. Cummins says they see a lot of snapped crank shafts due to differential harmonics. No damper in the world can manage that. The marine motors mentioned use a different crank.

The 5.9L springs for a 6BT - Bosch P7100 work and they're down rated in our pumps. So a 3400 rpm spring is about 2950 in ours. It's what I put into most of the trucks we've built. They're happiest under 2800 rpm - ish... every motor is different. Keep in mind, it's not just springs... it's the entire enchilada that keeps your motor safe and generates powers.

It's pump timing, fuel loads, turbo/air, air restriction and then of course, exhaust restriction and valve spring capability.

What do you do to the trucks that you build? I need some more power to accomplish my goal more efficiently but need reliability too.

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[grendel]

What do you do to the trucks that you build? I need some more power to accomplish my goal more efficiently but need reliability too.

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I made a few edits since you quoted me.

What is your goal?

 

[Ecscnvb]

I made a few edits since you quoted me.

What is your goal?

What do you mean you made a few edits since I quoted ? Have as much reliable power as possible.

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[grendel]

What do you mean you made a few edits since I quoted ? Have as much reliable power as possible.

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Read my previous post that I edited while you were responding.

 

[74M35A2]

Then you want an ISL. Same engine, but 400hp/1200ft-lb stock.

 

[Ecscnvb]

Read my previous post that I edited while you were responding.

Can't afford a new motor right now. I just need to get some more out of this 8.3 for now. I know there is some more power to be extracted out of it safely.

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[98G]

Can't afford a new motor right now. I just need to get some more out of this 8.3 for now. I know there is some more power to be extracted out of it safely.

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When you kill it (and you will), I have in-frame kits. Silverstate55 bought the rest of my NOS 8.3 blocks so talk to him for a block.

 

[Ecscnvb]

When you kill it (and you will), I have in-frame kits. Silverstate55 bought the rest of my NOS 8.3 blocks so talk to him for a block.

Kill the motor? Are you saying don't turn it up? What's in the kit?

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[98G]

Kill the motor? Are u saying don't turn it up? What's in the kit?

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In stock form it's a gutless turd that will live forever.

Turn it up all you want. It's still a gutless turd except now it will catastrophically fail at any moment.

You want more power? Put in a big cam Cummins with the appropriate transmission and transfer case. This is probably the cheapest way to do it.

The above are my opinions and observations. I don't expect to convince you.

The In-frame kit consists of 6 pistons and liners, wrist pins, main bearings and rod bearings, and the appropriate gaskets to rebuild your 8.3 while leaving the block in the truck.

Most probable failure modality will be to melt a piston. Second most likely will be to lose a bearing.

 

[Ecscnvb]

In stock form it's a gutless turd that will live forever.

Turn it up all you want. It's still a gutless turd except now it will catastrophically fail at any moment.

You want more power? Put in a big cam Cummins with the appropriate transmission and transfer case. This is probably the cheapest way to do it.

The above are my opinions and observations. I don't expect to convince you.

The In-frame kit consists of 6 pistons and liners, wrist pins, main bearings and rod bearings, and the appropriate gaskets to rebuild your 8.3 while leaving the block in the truck.

Most probable failure modality will be to melt a piston. Second most likely will be to lose a bearing.

Have you done anything to yours?

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[98G]

Have you done anything to yours?

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I no longer have anything with an 8.3, although I have had many of them in the past.

I currently have three 5ton trucks, and they all have the NH250. One of them was modified by the previous owner. It has EGT and a turbo, although apparently the fuel was not turned up. (It gets noticeably better fuel efficiency, and pulls hills noticeably better than the others).

Everything is a compromise. To gain performance in one area, you lose something somewhere else. My opinion - the military left a lot on the table in terms of performance. This went directly into reliability and longevity. I'm certain there's room to cut into that margin to some extent, without reaching the limit.

The problem is that you only find the limit by exceeding it - something breaks.

What task is it that you need to accomplish that a stock 8.3 won't do? And is that task within reach of a turned up 8.3?

Have you considered that the transmission is close to maxed out with the stock engine settings? (When you kill the transmission my buddy Lindsey has one still new in the can)

 

[aziator]

I no longer have anything with an 8.3, although I have had many of them in the past.

I currently have three 5ton trucks, and they all have the NH250. One of them was modified by the previous owner. It has EGT and a turbo, although apparently the fuel was not turned up. (It gets noticeably better fuel efficiency, and pulls hills noticeably better than the others).

Everything is a compromise. To gain performance in one area, you lose something somewhere else. My opinion - the military left a lot on the table in terms of performance. This went directly into reliability and longevity. I'm certain there's room to cut into that margin to some extent, without reaching the limit.

The problem is that you only find the limit by exceeding it - something breaks.

What task is it that you need to accomplish that a stock 8.3 won't do? And is that task within reach of a turned up 8.3?

Have you considered that the transmission is close to maxed out with the stock engine settings? (When you kill the transmission my buddy Lindsey has one still new in the can)

My buddy is an Allison mechanic with a large city contract and has been rebuilding Allison transmissions for well over 30 years. His advice to me, leave the engine alone so as not to blow up the transmission. He said exactly what you mentioned, they are about maxed out with the stock 8.3L...

 

[Ecscnvb]

I no longer have anything with an 8.3, although I have had many of them in the past.

I currently have three 5ton trucks, and they all have the NH250. One of them was modified by the previous owner. It has EGT and a turbo, although apparently the fuel was not turned up. (It gets noticeably better fuel efficiency, and pulls hills noticeably better than the others).

Everything is a compromise. To gain performance in one area, you lose something somewhere else. My opinion - the military left a lot on the table in terms of performance. This went directly into reliability and longevity. I'm certain there's room to cut into that margin to some extent, without reaching the limit.

The problem is that you only find the limit by exceeding it - something breaks.

What task is it that you need to accomplish that a stock 8.3 won't do? And is that task within reach of a turned up 8.3?

Have you considered that the transmission is close to maxed out with the stock engine settings? (When you kill the transmission my buddy Lindsey has one still new in the can)

Have a tree company. Pull equipment and use it as a dump truck. It does the job but lags when pulling equipment and loaded in the bed. Have heard governor springs, turning fuel up and advancing the timing will give it some wake up and not be to harsh on the drivetrain. What do you think?

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