Quote:

I read you can build up a street engine slant-six to get approximately 250hp on all motor.



My only comment is 200, MAYBE 225 all motor is more realistic. 250 NA, while not impossible, takes LOTS of experience with slants.

With forced induction, 350-600 seems (relatively) easy. Slants have overbuilt bottom ends, and they slant AWAY from exhaust/induction, making them PERFECT for turbos.

Good luck!

vm