Nope. The 170 and the 225 were designed side-by-side, from the very start. The engine size was not "increased" to 225. The valve sizes were considered ample for the 170 and adequate for the 225 in their intended applications. See if you can get hold of (many-decade Chrysler head engine engineer) Bill Weertman's 3-volume "History of Chrysler Corporation's Slant-Six Engine" from Chrysler Historical, or pick up Weertman's awesome Chrysler Engines 1922-1998 book.
You are correct, sir! I was referring to the fact that the only /6 you could get in an A body in the first year was a 170. There were no 225 Valiants 'till 1961, I think. I just said it wrong, and you are right.
Er…that's wrong, too. There was nothing "weak-kneed" about the Hyper-Pak; go read any/every road test of cars so equipped, and the accounts of how eight Hyper-Pak Valiants came in 1st through 8th in the NASCAR compact car races of '60 and '61 (and there weren't any after that because it wasn't much of a competition with the Hyper-Pak Mopars so completely stomping all other comers). Moreover, the Hyper-Pak kit was a good bit more complete than you seem to understand (going by your "a few parts" comment).
When I said "weak-kneed" I was referring to the marketing of that 225 Hyper Pack. I never saw one "in real life" did you? Scarce doesn't even do justice to the lack of those 197 HP engines in the real world.
They ran okay,but couldn't turn the rpm's that a 170 would, so that substandard head (for the displacement) kept them from being a stellar performer in class racing. I believe also, that the NASCAR Conpact race-prepared Valiant were 170... not 225s, because there WERE no 225=powered Valiants yet.
"Hyper-Pak kit was a good bit more complete than you seem to understand (going by your "a few parts" comment).
"
All I ever knew about was a carb/intake manifold, headers, 10.5:1 pistons and a cam and kit. Was there more? That's a "few parts" to me. What did I miss that was significant?
Sure, the stock head isn't conducive to massive airflow, but it's hardly the can't-get-around-it obstacle you seem to think it is. Those NASCAR Hyper-Pak Valiants were wound up to over 7,000 RPM…y'don't (can't) do that if the head's so irretrievably in the way. A carefully-chosen slant-6 head has a lot of room for porting and bigger valves. There's pretty constant chatter about wouldn't-it-be-nice-to-have-a-new-slant-6-head, and maybe it'll happen sooner or later, but consensus so far amongst those with fast slant-6 cars is that the head is not in the way as much as you seem to think it is.
They HAD to wind them up because they were only 170 cubic inches... and COULD. The 225 is a moot point because they didn't exist in Valiants, yet. I think the head IS in the way because these engines seem to pick up more than most, when a turbo is applied. Proof of the puddding, so to speak. Ported versions I have read about are lucky to flow 200 cfm, and given the displacement of a 225 cylinder, that's not enough.
Mmmm...no, not so much. The Australians and South Africans who bought factory high-perf 2bbl and 4bbl versions of it starting in '67 might disagree with you. As might the Argentinians who put their local larger "906" slant-6 blocks to good use and devised such droolworthy items as this 24v head.
We agree.
I dunno, maybe. I tend to think in E.T. numbers rather than horsepower numbers. There've been some pretty impressive E.T.s from slant-6 cars without forced induction, as it seems.
The only normally aspirated cars that have posted really impressive e.t.'s that I have seen are very light cars. There are turbo sedans running in the tens at 3000 pounds.
True enough…
Yup.