Here I go jumping in.........
I became a believer after sitting down for a bite to eat at lunch about twenty years ago. I noticed this old man sitting alone toying with his calculator. After a few minutes he notices I am emersed in an article on how to control detonation on particular cylinders of a given racing engine while other cylinders were ok. We strike up a conversation, and he explains that he is a retired engineer from Germany. The article explained that it was common practice to physically reduce cylinder pressure by the tedious process of removing material from the piston of the offending cylinder and rebalancing the recyprocating assembly until detonation was eliminated in order to achieve this to produce a dynamically sound engine which yields more power throughout the RPM range despite having different compreesion ratios from cylinder to cylinder. He explained that pratice was antiquated, and he and his company had been utilizing individual cylinder timing to achieve the same thing. YES THIS WAS OVER TWENTY YEARS AGO. I am only starting to learn how to do this with my MSD programmable digital-7 now! He goes on to say they also have incorporated other methods to help keep detonation at bay like employing a Methanol/Ethanol - Gasoline mix(sound familiar?) variable timing, and longer connecting rods. I asked about the longer rods and this is what he said. You divide rod length by your stroke and you will get your rod ratio. A rod ratio at or near 2.0 is optimum. He mentioned some of the same benifits that Squire, Wiseman, and Bigtime were talking about, but he went on to say two things that caught my attention 1, the piston had a longer "dwell time" at BTDC, which could benifit cylinder filling(normally aspirated applications) and at TDC, which helps the engine require less advanced timing, allowing a more complete burn and reducing the potential for detonation. and 2. Optimum rod ratio allows your engine to utilize it's intended design potential by providing a platform to work off of.
Think about it. Drag race type inductions, heads, camshafts, and headers are designed to make power by moving the max amount of air/fuel possible through the engine in the shortest ammount of time. The three most common ways to achieve this is supercharging/turbocharging, nitrous, and high RPM. High torque applications utilize a different aproach by overbuliding the application (i.e. 632ci mountain motors, usually employing 2 and 3 stage kits) to accomplish the same results. While it's the upper half that receive's all the attention, the bottem half is running out of steam well before realizing the full potential of the upper half. So as a result we see component failure and correct this by installing even stronger parts to compensate. The more power we dial in, the stronger the bottem end needs to be. You gotta ask yourself SELF! "Why is the rods trying to exit the crankcase as we increase horsepower while rev limits, static load (vehicle weight), and distance/duration (1/4 mile) remain the same?"
Here's an example:
Take two people (Keep it "G" guys), one tall with long legs, and the other short with short legs. Let's use them to represent our "long rod" and "short rod" in this example.
Now lets take them to the top of a hill and establish a given distance (like the 1/4 mile) of say 100 ft. . The for the puposes of this example the race will be going in the downhill direction to focus on the top speed aspect (where most bottem end failures occur). Soon after the race begins, the short guy's leg speed begins to "top-out" and results in the guy falling down (rod failure) because the increased demand is just too much for him to maintain. The taller guy on the other hand, continues to gain in speed and completes the course without incident. Now if you would shorten the hill to maybe 15 ft., I'm sure the shorter guy will have an increased usable operating range to utilize any performance benifits that he may have over the tall guy. You just won't win races after a face plant before realizing your engine's full potential. Cramming all the billet, mega forged, unobtanium rods with super light bob weight kryptonite crankshaft/hocky puck pistons in there is just not enough, and is a band aide fix at best.
Now I know there's gonna be alot of flack about this subject, I've got it amongst the guys around here. Smokey Yunick says to "STUFF THE BIGGEST ROD THAT YOU CAN POSSIBLY FIT IN THERE!". David Reher says "IT DOES NOT MAKE ONE OUNCE OF A DIFFERENCE, RODS JUST CONNECT THE PISTON TO THE CRANK."
Here's my .02.......You increase the stroke you mess with the rod ratio.
Poor rod ratios= Kaboom. High end parts and parts cycling just keeps you going a little longer, that's all. Don't cheat your azz out of fart.....fix the problem, not treat the symptoms. Still not convinced? Go check out the the WWII war birds......LONG ROD.
Turns out the old man was an engineer at Volkswagen. Wish I could've talked to him a little more.......when's the last time you heard of rod failure on a Volkswagen?
Aloha,
Mistah