Duramax/cummins conversions?

[Edahall]

Originally Posted by Skunksmash

What's the most horsepower that you can make with a 12 valve and not hurt fuel economy. Only thing that concerns me about the 12 valve cummins is they're what... 150hp stock? If I ever considered the swap, I really wouldn't want to go DOWN in hp lol. Down from my 350's already low factory 220hp, to 150hp... I don't think I could bring myself to do it.

Increasing horsepower doesn't necessarily decrease fuel economy if driven in the same manner. More often than not, it increases fuel economy.

The 1st generation 12 valve was rated at a conservative 160 hp. However, it actually put out quite a bit more than that. Even in stock form, they'll pull harder than a 454 big block. One big reason for the very conservative horsepower rating was because the rest of the Dodge truck (such as the transmission) couldn't handle more than that. That said, it is quite easily to get 300 hp out of these engines with just some simple adjustments. After that, it'll require different turbos, etc. The VE injection pump is limited to about 450 hp max.

The 2nd generation 12 valve with the P-pump is a different animal in terms of power. These suckers can put out over 1000 hp without too much difficulty. Everybody wants these engines for the big power so they cost more money on the used market.