Okay, I'm getting ready to start a project with Dart's BigM block, but confused on this standard deck vs. tall deck.

The only thing that makes sense would be the option to run a longer rod, but it's unclear how it would benefit performance.

Can anybody set me straight on this? Thanks!

This project will be bored=4.500, stroked=4.250 making it 540ci. At this point, we're uncertain if we'll use a power-adder (eg. blower).. we might even run alcohol. It's too early in the game to tell.  

There is very little to no power to be had by using a "long" connecting rod. From the research I believe a good rod ratio is between 1.5 and 1.9:1. A more important aspect of the engine is the piston weight and ring pack space that can be decreased/increased by changing rod length. In your case you should use a 'long' rod otherwise your choice of a tall deck will only add weight to the front of the car and increase piston weight with no advantage.  

Short BBC's aren't really designed for anymore than a 4 inch stroke without getting into the wristpins.A 1.5 ratio with a 4" crank and 6.135 rod is acceptable on short decks.Depending on application and the other issues related to tall decks,intake spacers,hood clearance,headers,distributor......then it's easier to stay out of the wristpins and have better rod ratios.Recommend internal balance crank kits,better on bearings at higher rpm's.Maybe there's some new rings for the wristpin issue for short deck 540 and 496's with 6.385 rods.   WIEDER  

Here's a good link on rod-to-stroke ratio:

http://www.strokerengine.com/RodStroke.html  

"Kind of like a vibration" above 5500 rpm? This isn't very good information if you ask me. John Lingenfelter built many 383's with stock'ish pistons and 400 connecting rods and I guarantee you that some of them saw upwards of 5500 rpm. How does side-loading present itself as a vibration?  

First post didn't take! Bearings and vibration connection is referring to external counterweights at higher rpms.Just picture a whipping wet noodle of a crank before you upshift.Low rpm engines that are ext. bal. with shorter rods will survive fine I don't argue that point.I just think of more friction with side-loading caused by shorter rods with is not good for higher rpm's.Internal balancing to me would be the way to go.   WIEDER