I'm no expert but maybe the Nissan is a Better chassis to adjust and make faster? Is that affecting these rules?

In theory it is, but I've never seen one that out-handled the other cars by a noticeable amount. At Barrie the r/t neons and 240's run nose to nose every weekend with the  rules they have in place. If the r/t neon only has to run 2200lbs at Sunset that's the way to go. As soon as a well built one shows up and dominates the division then they'll be adding 500lbs to them as well. I don't see why tracks can't hire a 4-cyl only tech guy. Sunset did it a few years ago, and the guy in the position knew his stuff. The problem is not "nobody can keep up with the 4-cyl combo's". The problem is the tracks have never hired anyone who knows anything about them. They all rely their old school carb'd V8 guys, therefor the drivers do whatever they want because they know they wont be caught. Guys start to spend 3-5 grand on motors, less and less people can win, and the car count goes down.

so how much will the dohc 240's have to weigh?

depends who you are whether you get weight added and how much. always ask Ted first before you race so you know what the rules are for that night and also that way you get an idea of what mood he is in

The Nissans from what I have read have to weigh 2500 lbs. the Nissan chassis is one of the simplest chassis' to set up in my opinion due to the fast that it is an independent suspension, rear wheel drive car that has 170 hp stock. Yes guys are now putting upwards to 5 grand into their motors.. To win what?! $250, maybe? This class is supposed to be an INTRODUCTORY class.. Does "introductory" not mean beginner class or for new people to get into the sport? If you think you can do well and think your a good driver, go to the super stock class and then see how you stack up.. The mini stock class is getting way way WAY out of control..