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high compression head volume

Moderators: Curt!, Pa

Post Sun Sep 28, 2008 6:44 pm

Posts: 83
I have a pair of aluminum high compression heads, 8.2 marks. I read in some posts here that this number means the "combustion chamber" in inches, right? But does it also includes the deck clearance volume and gasket thickness? If so, how much would be the head volume only? I measured the head volume - water - and it holds 120ml. Thanks in advance.

Post Tue Oct 14, 2008 3:44 am
Yes 8.2 is the nominal head volume in cubic inches. I've never seen Harley factory info to say if this included gasket thickness and piston clearance, but 8.2 cubic inches is 134 ml. Are these 7 or 9-bolt aluminium heads?

Post Tue Oct 14, 2008 7:31 pm

Posts: 83
They are aluminum nine bolt heads, stamped 8.2, so maybe they had been milled down for increase the CR or even to fix some gasket surface damage. I measured the heads with water, spark plugs in place, and they sure hold 120ml. At least they hold the same amount of water LOL. According panic's booklet this volume gives a 6:1 compression ratio for a 74" engine. Curiously I also have a pair of low compression iron heads, stamped 10.5, but they hold 9.3 inches of water, and not the number stamped in their casting...both heads milled down? who knows...
Thanks for the reply.

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