My 08 6.4 has 208,000 miles. It's starting to begin to have all the BS coolant pressure issues as usual. I have an h&s mini max, dpf ******* with 5" straight pipe, CAI. EGRs are still present but "turned off" in tuning. Getting to my question, would it be a better insterest in money to completely build my 6.4 (pushrods, pistons, RCD valve springs, h11 studs, bigger injectors, basically everything but connecting rods cause the price is outrageous) or should I do a 5.9/6.7 cummins conversion? I'm looking to get 700-1000 reliable HP out of this build. And no, I'm not going to get rid of this truck, too much sentimental value.

 

If it were me, I'd do the complete build. I'm planning a Cummins swap for my truck when the 6.0 decides to the bed but the 6.4 can be an absolute monster once all of the emissions junk is off and it has a little bit of work done to it. You'll be looking $5-10k for a complete 6.7 depending on mileage plus you'll have to factor in new motor mounts, modifying the wiring harness, transmission adapter plate...you get the picture. In both cases, the truck will be out of commission for a while. Cummins swaps aren't terribly difficult but getting all of the little gremlins worked out is a pain, my buddy did his last year and still doesn't have a fully functional dash.