Great Post Andy, I was gonna ask if you wanted me to ship you my 337, I'm glad you found one. was the 337 OOTB or ported? As I mentioned in another post the 'as delivered' 337 ports are only about 1/2 way between a 906 and a real Maxie, the 337 does have excellent taper from the plenum as delived though.

Please reiterate how much you felt the top-line Jesel valve gear/timing belt and dry sump may have contributed to the overall performance. I'm thinking somewhere in the area of 50-60 HP @ 6000RPM compared to a conventional wet sump/chain 'flexi-pedestal' system.

I would say OOTB the Indy 2D would definately be a mis match, but when you port it right that will narrow the performance gap quite a bit, and of course running the same Dommy with an open 4150/4500 adapter on a true dual plane would probably Skew the A/F and EGT's quite a bit....even still I'll bet the 2D torque (with the optimum jetting) between 3500 and 5000 was pretty insane.

If those EZ-1's worked that well with that 'not so great' exhaust port, I can only imagine what a full tilt -1 or equivalently MW intake ported SR would have done

I'm probably not the only one who would really appreciate seeing the corresponding Dyno powerband graphs; peak to peak numbers are cool and all but it's really way less than 1/2 the 'big picture' of how components perform against one another.

Looks like the 337 is the only viable "fit's under the hood" big single....you've inspired me to start porting it to get it to full MW size cause I think we can make up that ~15 horse deficit pretty quickly. It's even more impressive knowing it's a 4150 base which you would think puts it at a severe disadvantage to the 4500 flange competition.