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Why not just use the proven/bulletproof R5 block? An engine in the 420-430 CI range can be built easily.

I'm going to look at a complete R5/P7 next week, and that will be my plan if I end up getting it.



Initially that was the route I was going to take. I even ordered a crank from Winberg to go up to 400 cubes. After waiting 6 months for a one-off crank and with no firm deadline on when it would be done, I decided to take my money and go with the XR2 option instead. I feel like the XR2/P7 engine combo can be a viable answer to the small block guys who are craving more hp. Take a look at all the SB2 high horsepower combinations... no big secret that the heads are the key. I have had conversations with a few different well known head porters and they all agree the P7's have more potential than the SB2's. Unfortunately for us small block Mopar guys, there is no known proven recipe to use these heads in a 400+ cu.in. engine.



The exhaust guide could be offset a bit to get a bigger intake valve in to give it some air, the cam would be a matter of trying a few. I think a R5/P7 in the NMCA N/A 10.5 class would be a real competitive combo in a good car.