Just to be clear...

I really had no doubt the 337 would be a very good intake, both Andy and Dwayne's dyno testing proved that to me)...it's just that my particular 440 2D has a lot of porting and ( correct me if I'm wrong) everybody who tested their 2D's againt a 337 never had the level of deep porting this one did, and even on 572" motors ( Old Hippie and Firefighter both have 572's) the advantage of the ootb 337 vs the ootb 2d was clear to see ....but not really 'eye popping' dramatic, especially considering the heads and short blocks they were compared on. You all tested 2Ds, just not THIS 2D.

To put it another way I assumed the ootb 337 superiority would be even less dramatic ( if at all) against MY Ported 2D....thats really all I was saying because I ran the 2D with both the as delivered MW ports and ported even deeper than the Dr Air article intake. Before I ported it you could feel the ootb 2D was holding my 517 back by around 4500-5000, but ported that went away and she would pull hard all the way to 6800. I suppose the dual plane cross section hits a choke point as cast and the deep porting helped, I had to go up 3 jet sizes as result of the porting I did.

When I learned that my good friend Hollis Page (HPEngines on Moparts) had teamed up with 30+ year veteran NASCAR porter and engine builder Larry Smith, well, it was pretty much a slam dunk. I had the 337 for several years and I gambled that if I ported it it might be worth changing out the 2d for it, turned out to be the right choice. I supposed as much as I ported the 2d, this motor still wanted a bit more.

So to be fair, I never tested my ported 2D against the as cast 337 ( I wanted to do a back to back chassis dyno test but my gut was it would be a wash - A few less lb/ft but maybe a few more hp up top. Didn't seem worth going after to me. Add to that the motors tested probably (by the bench flows quoted) weren't quite as high flowing at .300-.600 as my Chapmans, so the torque/hp trade off might have even been less dramatic on my motor, not below 5000 or so anyway.

You can probably tell from the pics my 337 has been worked masterfully... And (ported to ported) there certainly is an improvement over what was already a pretty stout manifold. What suprises me is I never would have believed the ( already very good) throttle response and off idle roll-on would be better with a single plane over a pretty healthy dual plane.

Turns out the manifold and heads (and Fast knows these very heads hands-on) seem very well suited to one another.

I have a vintage Holley Pro dominator W2 tunnel ram I'd love to let Larry work on next! I figure I have close to Indy race intake flow...that (as Andy points out) fits under a stock hood and has better street rpm velocity for better roll-on torque and drivability.