I tried looking it up but cant find it.  

Your kidding right? A windage tray will help improve engine lubrication by controlling the interior windage at high engine speeds. By controlling the windage from splashing against the crank the factory claimed a 7 hp increase in power for a 340.  

I knew I would get that. No, I'm serious. Like I said before I'm pretty new to all this. I looked at some pics on places like Summit, but they don't tell how they work. I figured they went right underneath the crank, but I don't quite understand what exactly they do. What is interior windage?  

A wind-age tray is usually a stamped piece of sheet metal that is mounted between the crank shaft and the oil pan.  On slow revving i.e. stock applications there benefit is slight.  However race and high RPM applications claim that they actually free up more horsepower.  When the crankshaft is rotating say at highway speed a horizontal vortex of swirling air is generated.   The oil in the engine that was pumped up high and residual from the crank assembly is draining back to the oil pan gets caught in this vortex and is spinning too. Some estimate that anywhere from 1 to 3 quarts of oil can be caught in this vortex.  Which leads to why a wind-age tray is such a great thing. (1) this much swirling oil acts like a small load on the engine and robs HorsePower. (2) with that much oil NOT in your oil pan at High RPM you could have a potential oil starvation or cavitation problem,  KABLOOWE.  A wind-age tray acts like a scraper and removes the oil from the vortex letting it drain back to the oil pan.  It does not actually touch the crank shaft but it is close enough to it to skim off the oil and let it drain.  

Just imagine those big crank counterweights and connecting rods spinning just above a pool of oil 100 times a second. It creates a bit of a vortex as you might imagine. It's bound to pick up at least a mist of that oil and carry it around with the spinning assembly, right? Well, it's worse than that-it can pick up a whole lot of the total oil capacity at high rpm and just kinda wrap itself up in it in an extreme situation. That creates a lot of drag on the spinning assembly, and might even uncover the pickup so you lose oil pressure. Part of the reason for deep-sump designs is not just to increase oil capacity, but to move it down away from the crank. If you could move the oil level down 10" you wouldn't have much of a problem, but you can't because of ground clearance. The tray and any other pan baffling are about oil control. The baffles seek to keep it from sloshing out of the pan from g-forces, and the tray seeks to seperate the oil reservoir from the crank as much as possible-making the reservoir a semi-sealed package. They even use crank scrapers that are cut to just clear the crank and rods and skim off any excess oil. All this is why the ultimate bucks-up builds use a dry sump system with the oil kept in a seperate tank when rules allow. Most of the power savings are at higher rpm levels as you might imagine. Milodon has long been a mopar favorite and has good pans and trays. The MP tray can stand to have the drain-back louvers bent open a bit more. I would start building a little library of engine building books and you can peruse whatever subject at your leisure-always good reading for a motorhead.  

Thanks guys. I don't quite consider myself a motorhead yet, I'm just getting into all of this. I think what sold me on it was my friends 55 chevy. I've been looking for some good reference books, but I'm afraid to spend 30 bucks on a book and have it not help very much. This site is great, I've learned a lot from coming here. I also paid for a subscription about a week ago, so I should get my first issue in a few weeks.
I saw the pics of the trays, but I couldn't figure out exactly what they did. I figured it had something to do with the oil around the crankshaft but I wasn't sure. Anyway thanks again guys.  

A good book for the beginer is "How to Rebuild Small-Block Mopar-Engines".It covers 273-360 engines.This book is loaded with good info.  

Thanks 340 man