Hey all, I'm thinking about swapping to a cummins and need some input. I know I want a 12 valve and would prefer a 96-98, but I recently found a rebuilt 91 cummins bored .020 over with a rotary pump with a bully dog spring kit for $1400. What kind of power is possible and how would I go about intercooling it and could it be swapped to a p7100? Eventually i would like to reach around 850 lbs torque. So what I want to know is if the motor described above will work for building that kind of power.
Thanks!
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FYI, this post will probably get moved to the "Diesel Conversions" section...

Why a 96-98? What about the 94-96 P-pump engines? Or are you strictly out for the 215 hp pump?

Yes the rotary engines can be swapped to P-pump if you track down a pump, injection lines, front gear housing, pump support bracket, and other misc things. The rotary pump should be able to produce your torque target number with some pump tuning, better injectors, and a turbo upgrade. I have a friend with a 91.5 that laid down a little over 900 ft-lbs with a bench tuned pump and matching injectors (both by Sheid Diesel, with stock pump cam) and the Gillett Diesel 60mm compressor upgrade and 16cm2 exhaust housing on an H1C body. It's pretty smokey though.

However, given that your engine in question is bored .020 over (any idea why?) and the fact it already has Bully Dog, of all things, in it means it has probably been rode hard and put away wet many times. I would steer clear of it and hold out for a complete and hopefully less molested P-pump engine, if that is your ultimate end game.

 

Well I'd rather have the 215hp pump but I guess as long as it's a pretty pump it can be tuned to where I want it. Thanks for the advice and I'll keep looking for a motor. Also my truck has a zf5 in it will it hold up after a rebuild or should I be looking for a different tranny.

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why a 215 pump when you could have a 180?

 

There have been people who run the ZF-5 behind the Cummins, but after personally destroying a few ZF's behind the oh-so-mighty 7.3 IDI, I would look for an NV4500, NV5600 or ZF-6 speed (I've heard 50/50 on the ZF-6 behind the Cummins; I've read they shift quicker than the NV5600 or G56, but I'm not sure on the durability and they can be a pain to source cheaply in my experience). It takes a LOT of work to rebuild the almost-all-aluminum ZF-5, and to be done properly it needs to be machined out and sleeved where all the bearings meet as they have a tendency to spin bearing races and oblong holes in the aluminum case after some abuse (or so I've heard from a transmission rebuilding friend of the family who used to manage a medium duty Ford dealership in St. Louis).

It's all just hearsay until you choose a path and find out....