I don't think the JS pistons will fit the MAP con rods.get 10.5:1 and a thicker head gasket. Or 9.5:1 and thinner. Likely the former is safer.
JS Motorsport Compression
Copper cylinder head and base gaskets in various thicknesses are now available to adjust compression. Standard thickness is approx .040″. Adding .040″ to a head or base gasket will lower the CR approx…jsmotorsport.com
What about these - nothing in 10:1?
Complete set of two Norton lightweight pistons 750 to 1007cc. For JSM longer rods.
Norton pistons, Wiseco, JEjsmotorsport.com
Their website says 9:1 with.040 off the head. Wonder if their numbers are with a base gasket?Seems you get 8.5:1 or 10.5:1 compression ratio, nothing in between. My head has been planed and now 8.5 becomes roughly 9 or 10.5 to 11. I was looking for 10:1 Any suggestion on manufactures would be appreciated
Answering my own question:Their website says 9:1 with.040 off the head. Wonder if their numbers are with a base gasket?