Just scored a Super Six and matching trans

Insofar as ever seeing one in "real life," I take it that's a "no." (RE the 225 Hyperpack 197 HP motor.) That's what I meant about "weak-kneed"marketing. Mopar made practically NO EFFORT to get this package "out there."

"Was it the head, d'you figure? I'm thinking it was probably more down to the super-long stroke."

Well, lets look at a couple of things here RE the /6 head.

NHRA 500 cubic inch Pro stock motors turn 10,000rpm as a matter of course, and have a stroke that's well over 4". I realize that they have all kinds of engineering that enables them to do that, and make 2.4 horsepower per cubic inch (over 1,200) doing it, but that is a good indicator that long stroke motors CAN make HP at elevated RPMs. But, they need a suitable head to do it.

The 225 /6 has six individual cylinders the size of the cylinders in a a 300 cubic inch V8. Said differently, a 300 cubic inch V8 has 37.5 cubic inches per cylinder, just like a /6 does.

The "good-flowing" heads on the contemporary, 300+ cubic inch G.M. V8s that run well, all have intake flow capabilities in the 300 cubic feet-per minute range. Even the Cadillac Escalade LS heads "in the box" flow over 300 cfm. Lots of racers use these heads on their LS motor race cars, and run like crazy! 300 CFM seems to be a reliable number for a competitive engine in the 300 cubic inch range, if you want to go fast with a G.M. LS V8, normally-aspirated.

Slant six engines that have ported, "big valve" cylinder heads on 225's (same size cylinders as a 300 CID V8, remember) are limited to about 200 cfm intake flow, because of the original, small dimensions of the ports and valves. Our "big" 1.74" intake valves are the same size as an original 265 cid Chevy intake valve, which is an antique (1955) engine. The 1967 302 Chevy V8 (Z-28) came from the factory with 2.02" intake valves, and ports to match, but feeds the same displacement per cylinder as a /6 (225.)

Now, tell me again, Dan, about how "adequate" these /6 heads are for high performance.... Sounds like they need to flow about 50-percent more to equal the flow of these V8 heads. That's a bunch.

But, with enough boost, that all goes away, and the /6 can tolerate a LOT of boost, reliably!

That's why I feel that forced induction and the /6 is a marriage made in heaven!


Just my 2-cents,and probably overpriced at that...