Twins for a Cummins Big Cam IV NTC 315

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getblown5.9

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A buddy of mine has an 88 Freightliner with what was originally a BC IV NTC 315hp cummins, but it was upgraded by Antrim Diesel a few years back with heads, rocker boxes, injectors and a couple misc things to bump this motor to the 425hp range. Lately he has been hauling equipment for some road crews at night, and the name of the game is to be quick. Being able to make the runs quicker and getting 3 loads a night vs 2 is the best way to make money, so he wants to build a set of twins for the truck to keep the heat down and hopefully be able to help his 4mpg fuel mileage.

I believe it has a Holset on there now, but I need to figure out what size it is, and what would be a good match for it to build a set of twins.

But before i get ahead of myself, will this engine even be able to handle twins, or would he just be asking for trouble if he goes through with building them.
 
Head gaskets will be the first issue.
I'd advise him to upgrade to something in the 500+ h.p. range. You could buy something ten to fifteen years newer for what it would cost to compound that old club and keep it together.
 
I agree.

Search commercialtrucktrader. There are more than a few 450+ N14 and Series 60 trucks under $12k.

Maybe even consider water injection?
 
It would be my guess that it's a 0838 cpl number, that is working against you from the get go, 17:1 pistons don't play well with high boost numbers on a big cam.

I would stick with a HT4 as a single, good for almost 800, if that's what is on it then the turbo is not what is holding that engine back.

I have thought about building a smaller set using a HT3 or HT60 as the high pressure charger and building of that, but haven't got around to it.
 
have him look into converting to full flow cooling, and wether his rear end gears and number of transmission speeds match the increased hp and specific usage for the truck, the old 855's are great engines
 
You might see if you can find a set of the 475tt turbos. They'd bolt right on and support big #'s but he'll need to pull the timing way back to keep it from doing the head shuffle, especially if it has 17:1 like smokincat said.

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Charger said:
have him look into converting to full flow cooling, and wether his rear end gears and number of transmission speeds match the increased hp and specific usage for the truck, the old 855's are great engines
Click to expand...

As many gears as this guy.
[ame="http://www.youtube.com/watch?v=VvB8xkRoH7E"]YouTube - Broadcast Yourself.[/ame]
 
chevota84 said:
You might see if you can find a set of the 475tt turbos. They'd bolt right on and support big #'s but he'll need to pull the timing way back to keep it from doing the head shuffle, especially if it has 17:1 like smokincat said.

Sent from my DROID X2 using Xparent Blue Tapatalk 2
Click to expand...

If it does happen to be that way, everything is matched to make that engine work, the timing is set weird as it is. 0838 and 0840 cpl numbers are not the best choices to do much of anything too.
 
Charger said:
have him look into converting to full flow cooling, and wether his rear end gears and number of transmission speeds match the increased hp and specific usage for the truck, the old 855's are great engines
Click to expand...


He said something about it has a high volume, low flow cooling system. I do not know much about these larger engines at all, but this is his lifeline and he works it 5-6 days a week hauling dirt/stone out of the quarry, but he pulls some equipment whenever he can to make extra money, so it has to be reliable. If twins are pushing it too much then he wont do it and just deal with it for now.
 
To convert it properly it would need to have the radiator, oil cooler and the restrictors taken out of the water manifold, plus some other odds and ends.

The top water hose from the radiator to the engine might be a 1.25" maybe 1.5". In comparison the top hose on my engine is 2.5" and bottom is 3".

It would be at the top of my list to make sure it stays cool before I went to far on engine mods. Just my 2 cents.
 
FWIW , the cam in those formula engines are crappy.

If purchasing a bigger hammer is not an option, I'd recommend about 250 pounds of fuel pressure with the right turbo (HT4C).
 
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