What are the max engine limitations you are allowed to have in the monster truck class in ROAR? Thanks

ROAR and RC Pro allow up to .28 sized engines in any Monster Truck or Truggy.

http://www.roarracing.com/downloads/2007rulebook.pdf

Ok, thanks.

According to the rule book, it does not specify engine modifications. Is there an addendum that explains the sanctioned rules concerning engine mods?

As far as I know, there are no rules that cover engine mod's. Many sponsored and factory guys run modd'd engines. It might make sense to include a stock and unlimited class, except that there is only so much time in the day and more classes add to the time to complete the race day. Besides, in the end having a professionly modified engine doesn't make as much of a difference as having a lot of time on the track.

I agree. Driving skill is paramount. But when you get to the nationals, all the drives that made it are so very similar in skill (that is how they got to the championships to begin with) that skill is basically equal between evreyone. What actually becomes a major factor, barring errors and bad luck, is material quality. What I mean is given two very very good drivers with equal or very near equal driving skill, the differnce that decides the winner could be the car and engine. These drivers would be so skilled to begin with that they could push their vehicles to the very edge of the material capabilities. I.e. they have the skills to utilize every last gram and every last oz-in of their cars and engines.