"TURBO. (period)
The /6 head is a big throttle valve stuck on low."
I am glad to see that somebody "gets it" with regard to the slant six cylinder head issue.
Though there have been countless examples of attempts by some pretty knowledgable hot rodders over the years to make a significant amount of power out of a naturally aspirated slant six, in these "exercises," they have never gotten much over 300 horsepower because that cylinder head, even when ported to the max and fitted with the largest size practical, valves, just won't flow enough air to generate the kind of power we'd all like to see. Car Craft (or, maybe, HOT ROD) magazine did a feature story (and, it's available, online,) on a full-race version of a slant six a few years ago, and the engine builder pulled out all the stops; even built an EFI system for it....! A lot of professional work went into that engine in an atttempt to make as much power as was possible, with the final result generating a little over 300 horsepower.
There are exceptions (aren't there, always?) to my contention, however; two come to mind... the Team Green 1961 or '62 Lancer that beat a new Hellcat 3-in-a-row, last year, running low, low 11's. Just as impressive, is the MAD MAX car from California, another naturally-aspirated early A-Body that runs exceptionally fast! Both of those cars have been subjected to weight-removal in the extreme, though, and are nowhere near the curb-weight of most A Bodies. I think they both weigh in the neighborhood of 2,200-2,300 pounds. My car, a '64 Valiant, 4-door sedan, (which is just 35 pounds heavier than a two-door, post) has the back seat and door panels removed and has no headliner, no front bumper nor brackets, no radio and no heater, and no power anything. It still weighs 2,700 pounds, ready-to-race. That's seventeen-percent more than the two "lightweights" I just mentioned. On a 300-horsepower engine, seventeen-percent would be fifty-one horsepower...
Tom Wolfe and Ryan Peterson, both FABO members, have both built turbocharged 225 slant sixes that generate just over 500 horsepower... They have never had those engines on any kind of dyno, but Ryan's '66 Valiant weighs almost 3,000-pounds (including driver weight,) and has gone 127 mph in the quarter. while Tom's '70 Dart is heavier at about 3,350 pounds, so runs a quarter-mile speed of 120 mph... about the same power as Ryan's, according to the Wallace automotive calculator.
The difference from naturally-aspirated to turbocharged is dramatic.
Those runs, referred to here for reference, were made on twenty-eight pounds of boost in each car, which is a lot, and not something you'd want to utilize every day, but it doesn't seem to have damaged their engines.
I built a clone of those two engines for my car, but am basically, chicken and have yet to go over 15 pounds of boost...but, will. soon, out of curiosity. At 15 pounds, my car has run a 6.60 eighth-mile at 91.5 mph. That equates to a 12-flat at 112 mph, quarter-mile, according to the Wallace calculator.
I am pathetically ignorant, of forced induction AND slant sixes, this being my first of each, so, I have run up a considerable amount of blind alleys, wasted hundreds of hours by doing some things twice and others, three times, so, I must apologize to anyone who has followed my halting progress, and has had the patience to endure what must have seemed like an endless string of excuses from me as to when something MIGHT get done... I AM sorry.
But, at age 77, I figure if I can still fog a mirror, and turn a few wrenches, I am one lucky S.O.B., and I will stay with this oddball, weirdo, project 'til I am satisfied that it runs liked it should.
Update; I have had miserable (1.90) 60-foot times because the exhaust side of this 66mm turbo is just too big and won't spool quickly-enough to give me the grunt I need to launch energetically-enough, so, I am currently installling a 50-hp nitrous system to help spool the turbo. Once the turbo is spooled, (about a half-second, or so...) the nitrous will shut off, completely. I don't need it for the rest of the trip...
Wish me luck!
It is ONLY my opinion, and, you know what they say about opinions... but, to me, a slant six without a turbo is like a rhinoceros without a horn!
But, that's just me...