yes thanks, very helpful, didnt want to hijack someone elses thread tho.
So honda isnt being very helpful with engine number. Is there somewhere i can find out what my MC16E-1040461 is?

Also whats the deal with pistons? tygas mc18 top end kit comes with a 21 unmarked piston, and the 21 kits letters dont match the piston letters they come with? is it just the head gasket that is different between 18s and 21s?

The rebuild guide on the main site is awsome, very informative.
Is there anything else anyone would recommend doing during rebuild? while everythings opened up?