sorry for the confusion, I think I already posted this. Here I go again. What is the biggest engine upgrade I can do to my tornado bb. I doesnt matter the engine brand. Also, will I have to beef up any chassis components. Thanks again.

Polish and porting...

well, you could put how ever big an engine that you want in it but it would take alot of modding. also it would be to much for the car to handle. you would be blowing gears like crazy. a direct drop in would be a OS cv-rx.18. lotsa power. If you want even more power, get a os tz.18. its enough power to be blowing you gears out but it would be alot of fun. you wouldent have to modd much for that motor ither. its a rear exuast port so you would have to buy a new header

I agree with Jumpanddrop.....
A big block is unrealistic unless you have Mad modding skills and it would be almost undrivable anyway.
Personally, I would use Redcats exchange program and go with the sh.18 motor. Then get a Motor Saver Air filter and a Redcat Header. Then buy a good quality Pipe. You will be Surprised at the difference these changes will make!