thanks jmac i was planning on running 95 or 98 octane with the higher compression from the flat top pistons. But how else can i raise the compression to 10.5:1 or even 11:1? would that involve shaving the head, and decking the block? and the closed chamber oval port head your talking about is that from an a14/15? Head work is in the pipe line but just not yet. Ive already gone over budget on the first stages of this build and im getting all the machining at a discount, parts at trade and doing the work myself. I am a qualified mechanic im just new to modifications and have never really had the opportunity to do this sort of work.