A few questions about 1st generation 12 valve

[79gmccrewcab1t]

I am at the start of transplanting a 1990 non intercooled 12 valve from a school bus into my truck and had a few questions about this engine. From what I read cummins changed the injection pump in 1991 and added a intercooler to the 12 valve, can either one of these be adapted to my engine, and do I need to go to a larger turbo before I add on a 4''.
Also what kind of torque and horse power can I realisticly exspect from this engine without reinventing it? Any help would be greatly appreciated

 

[argve]

Injection pumps are interchangeable the calibration settings on your current pump can be changed to gain the usable power with the intercooler and larger exhaust. The turbo you have on the engine currently is plenty enough but you may want to increase the turbine section size to help it breath easier. Going with 4inch all the way back will allow you room to increase the fuel via larger injectors and more tweaking on the injection pump.

 

[79gmccrewcab1t]

Cool thanks for the info. Can hardly wait to get started

 

[rebel_horseman]

The only thing that changed in '91 was the injectors. The '91.5 trucks used a slightly different injector tip that didn't flow as much fuel as the non-IC trucks. The '91.5 trucks also came equipped with the 21-cm2 turbine housing as opposed to 18-cm2 on the rest of the trucks. That's why they are called the lag-master turbos because it takes forever for them to spool. The 4" definitely helps temps, but if you go too far you'll need to upgrade the turbo to allow it to flow more air and get them temps down.

As far as numbers, 300 HP at the wheels is easily attainable with only a little bit of work. Definitely upgrade the fuel pin to one that will allow you to get enough fuel through the pump...I have the DennyT stage 2 but the Stage 1 would probably smoke less. And also install the 366 governor spring, which also makes a world of difference in drivability and also frees up some lost HP.

If I had to guess, my truck is probably in the neighborhood of 300 HP and 700 ft-lbs, more than enough to do what I want. And I get 19.5 driving 70 to work and can touch 22 if I drive 55 and keep my foot off of the smoke pedal.

 

[79gmccrewcab1t]

Ok so correct me if I'm wrong, I wont need to go up on my injector size cause they were larger to begin with?
And another question,when I was driving my donor bus to the shop to strip the enging I noticed the RPM's were sitting at 4000 going 65.The previous owners said it could run like that all day long but it kinda makes me nervous. Does this sound right and if so do I still need to go to a 3200 spring?

 

[rebel_horseman]

If the engine is originally a non-IC engine, the injectors will flow plenty fuel to get you to the 300-350 HP range.

It's interesting the RPMs were so high. You may already have a 4000 RPM spring in it and if that's the case then you do not need the 3200 spring. The Dodge trucks came stock with a 2400 RPM governor spring and the extra RPMs are great. And, since it was built by Cummins with that RPM spring (I'm assuming) then yes it can be run all the way to max governed speed all day long.

You might want to check the Cummins ID tag on the driver's side of the engine on the timing gear cover. Get the Cummins Parts List (CPL) number and do a search on the web to find out if the motor originally had a 4000 RPM max speed. That CPL will also tell you the OEM power levels.

Lastly, if you're turning up the pump you'll need to supply the VE with more fuel. The lift pump that came on the Dodge trucks was OK for stock (or slightly more than stock) applications but not much more. Most of us have upgraded to a low pressure piston style lift pump similar to what came on the 2nd Gen Cummins trucks. These pumps will be plenty adequate for stock to moderate power levels. The entire kit can be found here: http://www.dieselautopower.com/product_p/12v 1st gen piston pump.htm

 

[79gmccrewcab1t]

K i'll do some surfing and check out that spring.

I had seen those lift pumps before and was planning that with my next purchase.
Before I had shut the engine down to pull it I noticed fuel had been leaking badly from the injector pump but couldn't see the exact spot. How difficult is it to pull the injector pump from this non intercooled and does it require any special tools or tricks, and after its pulled do you have any place that you would recomend sending it to have rebuilt and it turned up?
Thanks for your help

 

[rebel_horseman]

The pump looks like it's a chore. I haven't had to remove mine. There are 3 bolts holding it to the timing case; 2 are fairly easy to get to and one is a monumental pain in the butt to reach as it's tucked up behind the pump between it and the block. Cummins makes a special half-moon shaped wrench to reach the bolt. Having the motor out may make a world of difference as you may be able to figure a way to reach it.

Piers Diesel is up in your neck of the woods and they can probably do everything you need, or at the very least point you in the right direction/. There are a lot of good folks up there with these trucks. Check the Northwest Bombers site, CumminsForum, and 1stGen.org for any specific info or help.

 

[79gmccrewcab1t]

Yeah prob would be easier with the engine pulled thanks again for your help