Well… a 130-ish HP V8 in a full-size car is kinda hard to get excited about 😂
I never really bothered to learn about Chevys smaller than 350, but sometimes there are advancements (especially in that era) in head design for efficiency or emissions that leads to new engines that appear similar. The LS series was absolutely dominating V8s and Chevy went ahead and designed the LTs because of direct injection & other advancements.
It’s nearly the same where, a few years ago, the German Engineering Borg determined that 500cc cylinders and nearly square bore & stroke delivers optimal combustion with minimal mechanical losses for the cylinder size. It’s why over the past few years we’ve seen so many 2.0L 4-cyls & 3.0L V6s from Deutschland, and then top them with two turbos to generate relatively huge power with a nearly optimized ICE 😎
The 307 was rated at 195 HP, although that was under the old system (gross vs. net?).
It's always surprising to me how light those old cars were for their size. I just found a site that listed the curb weight at 3690# (though that was for the 6-banger and manual transmission - say 3800# for the 307/PG)?
Interesting to hear about the German engineering conclusions. I'd heard that it was a tradeoff between thermal efficiency (and thus fuel consumption) and top end (and thus power).
The theory is that a narrow bore results in less surface area for a given displacement, and thus better thermal efficiency.
However, to achieve the same displacement then requires a longer stroke, which limits the maximum piston speed and results in more reciprocating mass.
As well, a narrow bore limits the size of the valves, and therefore limits how well the engine can breathe.
My 307 was hard on gas (rare to break 20 MPG Imperial on the highway) whereas I remember a couple of delighted 305 owners claiming 26 MPG Imperial, which was very good for the day.
But that's not apples-to-apples either - my 307 was old and tired, running in a big car, and coupled to a Powerglide; the 305s were in Novas or Camaros, and would have been paired with 3-speed TH transmissions.
The 307's 3.875" bore would have certainly allowed for better breathing than the 305's 3.736". Remember that the valve area increases with the square of the diameter.
The 307's stroke (3.25") was significantly shorter than the 305's (3.48").
I'd love to see a controlled comparison of these two engines (i.e. installed in two identical cars).
So back to the Germans - looks like they figured a square (bore = stroke) is the best compromise, and get around the valve size with forced induction. Makes sense, and it seems many other manufacturers are now going that way.