Piston 11:1 or 10:1

[Got_Mort03]

I am rebuilding the top end on my 03 400ex and i dont know what cam, and piston to get a 10-1 or 11-1. will the 11-1 blow the head gasket or will it be fine?? The engine is completely stock all i have done is put a pipe and filter on it so far...any help would be great:)

[ghak99]

11:1

[4TraxRider]

Definately get the 11.1. Your gasket will be fine and you'll love the added power. While you have your engine apart, you might consider a new cam to take advantage of the new topend.

[RED121572]

11.1

Remember, replace those headbolts with at least brand new stockers!!!!

[SnellCRP]

With a stock 400ex unless you can measure the volume of the combustion chamber and the compression ratio of the piston your compression will probably not be a "true" 11:1 so I would definitely go with the 11:1 if you want a noticeable increase in power. You also could bring the deck height up to increase the compression by using thinner head gaskets, but unless you have the tools and measuring equipment I would leave that to your engine builder.

[quadmxracer]

Definetly go with an 11:1 it makes a very noticable difference, and I would also suggest a new cam also to bring out more power, and if you got the dough have your head ported and polished. Also consider a full exhaust. Just my 2cents.