I have something to add about stroker rod ratios, but it's about 385 big blocks and BB's in general though. When I was doing the dyno work on my present blown engine I first fired my 4.5 inch stroker with 6.6 Chev. Eagle rods and stock flat top pistons. After foolin' around a bit we switched to 6.8 inch rods and power- forged pistons (same flat tops and compression ratio) that weighed the same. The difference on the dyno was not subtle. The second piston rod combo. made over 125 more ponys@ 6500 and about 70 at idle. The second combo also rev'ed up much quicker. More about that later. Blowers tend to bring out such things between setups really quick.
In 1953 Chrysler did several studies on hemi heads that come to the conclusion that a 3300 feet per minute piston speed was optimal for the intake stroke of a naturally asperated engine. This report said that stroke/rod ratio's (stroke into rod length) of 1.6's to 1.9's was optimal. Generally speaking, below 1.6, a engine won't rev. (rod angle greater than 15.5 degrees varient) Above 1.9's due to higher bob-weights it won't rev. Remember too that the actual power numbers may be exactly the same in this range.
In 1966 G.M. released a famous white paper on it's new 396/427 that was a virtual mirror copy of the Chrysler paper from the 50's.
Same 3300 target piston speed number at 6500 RPM's. They showed the math for a 427 with stock stroke and stock rod length that optimized the then new square port heads to you guessed it, 3300 feet per sec. piston speed, for a 427's displacement, at 6500 rpms. When Chevy up'd the stroke of a 427 to 454 and left the rods alone savy drag guys knew where they messed up. Cube for cube the 427 ran better than the 454, it was the rod angle that changed. Power stayed the same. The measured voumetric effeciency for the 427 at the intake valve was over 100% on the head at 6500 rpms. It droped off to the high 80's for the 454 's larger intake charge. But the net intake airflow was the same. So Chevy rated the 454's power at 500 rpms below the 427. Hmmmmmmm.
People, it's not got any better since then. Yes, todays small block heads have caught up with thinking that Bill Grumpy Jenkins and Chevy was talking about way back in 67. (together with combustion chamber designs)
Todays thinking at the big three puts the rod ratio's right square at 1.75's because that's the best combo. for overall considerations. You guys can do the math on your favorite brands. I know I did that, one bored night. And when I plugged in the numbers on various famous winning engine combo's, certain things popped right out at me.
Remember too that we we have gone from stroke/bore ratio numbers of around .75's in the 60's and 70's, to the presant thinking in stroke/bore ratio's around .9's. And longer, lighter rods are in that equation, together with better head designs. At a 3300 ft. per minute piston speeds of course. JUST KIDDING.
For hot rodding in general the longest rod you can jam into the hole is the right one for a street car. There is NO disadvantages other than bob-weight and fitment issues. Even if your rod ratio is too long and the your heads are the latest maxed out super duper flow monsters, you can cut back to a smaller head. In the real world most of us don't use such heads. And we run our headers through sidepipes or mufflers. So the long rod ratio's work for most of us mortals using normal stuff. And that's a lesson the big three finally figured out.
Racing engines are the exception, but it's amazing to me that the 500 cube pro stock motors out there all run 7 inch rods w/ratio's around 1.8's. I know, I just got off the phone with a local pro stock engine builder that supplies engines to the pro stock crowd. And he concoures with what I just reported above. He also claims that his engines make more power per cube than a NASCAR cup engine too. Guess he doesn't worry about gas milage either, like the cup guys do.
You guys need to look a bit better at what the factorys are doing, and a little less at what the hot rod books are saying. Even the factorys have race cars, and they usially win.
cobrashock