207 is the way to go as far as a factor block is concerned. Sean (ASG) had a stock block 207 in a GC8 running 10.2 @ 137MPH at the drags, which was making 440hp on pump and close to 500hp on race fuel. Although it is arguable how long that motor had left after it was sold 10,000km later.

Even if you needed to build the motor from scratch a 207 would be preferable in my opinion. That is not to say that a 257 can't make that power, it is just their fatality rate is higher when it comes to built motors.

If you did a 257 with a set of rods and pistons it be a killer motor still, and it could get you close to your planned goals. There have been few 257 motors with just pistons making easy 340 - 350HP (pretty sure one of Justin's Libertys had this for over 30,000km).

But to see a streetable motor that will handle 400hp look at Daz's build (or Tinos for balla $pec build). To be honest Daz, Justin or Troy need to chime in and write an essay and school us all.

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MY01 JDM EVO VII - 230KW / 430NM @ 1.6BAR