12V rebuild advice

[SEdgar]

hey everyone! I was wanting some input on rebuilding my 98 12V Cummins. I am fairly new to the 12V world.
I LOVE my 98 it’s my daily driver, I am wanting to build my Cummins with reliability and fuel economy being first priority, with out sacrificing too much HP and torque. I have about 7-8 k to invest, and want to get the most bang for my buck. Any advice you could offer me would be greatly appreciated! I am considering buying a used 12 valve from a school bus to rebuild and replace the engine that is currently in it, and then rebuild the current engine as I have the cash. Thanks!

 

[GAmes]

Why do you feel your engine needs a rebuild? Is it burning a lot of oil, like a qt every 1000 miles? Does it have excessive blowby? It is reliable from the factory, mileage and power can be improved. You don't have to sacrifice anything.

 

[SEdgar]

It doesn’t burn any oil, and no blow by. It does have close to 500,000 on it. I plan to use it to pull a 25’ enclosed trailer on a very long trip. I thought it would be a good time to get it rebuilt and replace any parts that are worn out so I’m not stuck on the side of the road. What would you recommend?

 

[Stox5225]

Well, aside from a complete rear down which may not even be necessary, I would say pull the head and freshen that up. It will give you the chance to inspect your cylinders and pistons and let you know if you need to dig further. Breathability is key to these things, so I would personally have LOVED the finances to get my head ported and polished. Would make my cam more useful. For 8k, I would say:

Valve train refresh with heavier springs
Port and polish head
Moderate cam shaft like a Colt Stage 3
BW K27
5x.012 injectors.
AFCL
Aftermarket exhaust manifold.

Make sure the transmission can handle it. I don’t know jack about autos (if that’s what you have), so that could get pricey causing that above list to shrink.

My .02

 

[SEdgar]

The transmission is automatic, but I replaced it with a BD aftermarket transmission, torque converter and transfer, it’s built to handle 1000+ HP so I’m good there. Thank you for the advice, I am going to have the head bolts replaced so while the head is off I will go through it and see what it needs.

 

[GAmes]

At 500,000 miles mine didn't burn any oil or have blowby either. I towed literally hundreds of trailers bigger than a 25 ft enclosed all over the US and Canada (before and after 500k), including a trip to AK with my 13,000 pound 5er in tow. At about 750k it started to burn some oil. I replaced it at 800k. If it is working leave it alone.

 

[Cummins12V98]

If you have not changed out the injectors a set of stock Bosch 215's will help with power and economy.