I called cen and spoke with mike, he told me I would need the .18 head to ensure a tight fit.... i left whatever head gaskets were in place from the nt16 in place... I don't know if its bent or not.. doesn't matter anyway as my os engine arrived today... won't get a chance to do much until next week as I hve to go to Boston for the weekend... Girlfriends family stuff..... I will not give up on the cen engine, I'll get a new gasket and try it.. maybe i'll compare the 2...