416ex gasket and timing chain ?'s

[yzbill]

Ok i might buy a used 400ex and do up the 416 kit. I have read enough about these and figured i might as well replace the timing chain so my ? is i hear people talking about using different gaskets and it messing with the timing. What if i just bought a xr400 head and base gasket and put in a xr400 timing chain as well would'nt this all work perfect(and the chain not have that extra slack) in the 400ex engine?:D

[Bad Habit]

The xr400 are not going to affect the timing, they're going to affect the compression ratio because the head gasket is slightly thinner. I guess in reality, the cam sprocket is going to be very slightly closer to the drive sprocket and would, in theory, put more slack in the timing chain, but the chain tensioner will easily make up the difference in slack.
I'm not for sure, but the EX and XR timing chain are probably the same part numbers.