Join Date: Sep 2001
Location: lexington, ky, usa
Sorry to disappoint you, but the SBC wasn't built to be *perfect*. The key word is EVOLUTION.
VERY rarely in engineering do you start with a clean sheet of paper, and say, "What would the perfect widget look like." Usually, you take a widget that already works, and put a new twist or two on it.
Chevy developed their V8 to give more power, and less weight. But, it was an evolutionary, not a revolutionary design. It was just an extension of their existing inline sixes.
In my driveway sits a neglected 1951 Chevy Half Ton pickup, with a 1956 235cid inline six cylinder motor. The 235 has a 3 9/16" bore, and a 3 15/16" stroke. The 216 it replaced had a 3 1/2" bore, and a 3 15/16" stroke.
Somewhere I have an early ad celebrating the Chevy V8 -- weight was the chief advantage touted. Other manufacturers tried Inline 8s to get the power of more cylinders. The V8 thrived while the Straight 8 died; due to weight, and life of the l-o-n-g crankshaft needed for the Straight 8.
And don't forget ease of manufacture. V8 engine blocks are cast from iron -- they needed to be relatively cheap and reliable to pour, for mass production.
But, evolution is pretty efficient, after all. If you were to start from scratch, you probably wouldn't end up too far off of where the SBC ended up. Cylinder size (bore) is limited by several factors. Speed of flame travel is one -- with too large a bore, you can't get full combustion. Stroke is also limited by several things, including what's already been mentioned here -- rod speed being one of the bigger ones. So with roughly a 4" bore, and roughly a 4" stroke, you've got a pretty good picture of what the "ideal" V8 would look like. (Maybe NOT ideal to a TC gearhead, but ideal for mass production.)
Want more power? The best (easiest, cheapest, etc.) way to do it is more cubic inches. Already got a ~4" bore and a ~4" stroke? Add cylinders. That's how we went from the inline six to the V8, and have you seen the Dodge V10?
BSME Washington University St. Louis MO, 1992
"Soon to be... 383"