Xu9J4 / Xu10J4Rs

[mollisk 2 1 Cars]

Does anyone have experience of fitting high compression pistons into a XU9J4 bottom end fitted with an XU10J4 cylinderhead. Inparticular I would like to know if there are any clearence problems due to the diameter of the exhaust valves and the geometry of the combustion chamber with respect to the piston pretrusion.

 

Thanks

 

mollisk

[welshpug 1,657]

do you mean the 10J4 or the 10J4R?

 

same valve sizes regardless though, and I believe the centreline and inclination is the same, I'm sure someone like Sandy could confirm for you.

 

its the 10J4RS that has different valve diameters where you may need to enlarge the exhaust cutout radius.

[mollisk 2 1 Cars]

It is an RS head that I am planning on using.

[welshpug 1,657]

exhaust valve is larger by 1mm iirc, so you need to confirm what the radius of the XU9j4 valve cutout is.