40 zize engines good new
 

with the demise of the irvine 40 next choice OS 46AX , they did change the shape of the crankcase sort of an unequal pentagon shape, the good news is head bolt spacing the same ditto on bore of liner. The Davis head fits the new AX46 along with the older one I have the older one with Davis head which is the new style
flat top anular rings machined in the side martin