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Originally Posted by bigbrownbird
Hi guys,
Smokey Yunick once said, "put the longest damn rod that you can in an engine." Obviously, going with long rods and a stroker crank would give a power boost. But what about putting longer rods and shorter pistons with a stock crank? It should build more power, but how much, and where in the RPM range are we talking? Is this a good practice to be doing on a street engine? And the most important question, Is there a set of long rods and short piston for a 474 (460 block) and are they justifiable in price for power? Just a thought running through my head while staring at my block on a stand...
Thanks guys,
Lee
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:: puts on his Mechanical Engineer hat:: Okay, longer rods...
Yes, longer rods are better. The longer the rod is, the closer the piston gets to perfect sinusoidal motion, which decreases the maximum instantaneous speed and acceleration, as well as increases piston dwell time, so that combustion gets closer to perfect constant-volume combustion.
All that engineering crap to say that the longer the rod, the higher the compression ratio you can run on the same octane without knock. Your engine will also be more efficient. Now, it won't be
that much more efficient (and remember, efficient equals power) for the same compression ratio, but like I said before, the magic of longer rods is that you can run higher compression without knock. And increasing compression is where you really get the increases in power and efficiency.
The longer rods will also decrease stress on your crank, due to lower accelerations, if that is something you are concerned about.
This whole stroke/con rod length ratio issue is actually why I really like Mopar engines, and why I would really like to build up a Dodge 383 into a solid-lifter high RPM screamer. It has the bore of a 426 but the stroke of a small block. And rods a mile long to boot. Excellent... ::tents his fingers::
Anyway, hope this wasn't too boring, and I hope this helps!
Mike