what exactly would i need to do to my engine if i changed my 400ex piston to a wiesco 10:8:1 piston. whats the next step after adding this cam?! would i have to change the gas at all? thanks

 

or the 11:1 ross racing piston?

 

Anytime you bump up compression, you almost always have to go up in octane on your fuel. You run the risk of having detonation with too high a compression without the proper fuel. The best thing to do is to contact someone who specializes in 400EX motor upgrades. If you get a certain piston from them that's going to increase your compression, they should be able to tell you what octane you need to run.

 

i was told you could just run regular fuel as long as its not over 11:1