12:1 piston

[hippy440]

if you used a 12:1 weisco piston with xr head gasket and no base gasket what comp would you have?:confused:

[400exJOE]

I think that the compression is for the xr400. When I put on my 10.8-1 piston w/ the oem thickness for the 400ex it comes out to 10.5-1. So figure 12.0-1 plus maybe .3 extra for removing the base gasket.