Thanks Derek, that is quite a formidable spreadsheet !.
And that thickness is consistent with Roger Williams who says in both TR6
books that the US head will need about .080 removed to bring the compression
back up to 9.5:1
According to Richard (zero decked, standard pistons) 3.5 - 3.416 = .084 for
9.5:1 CR
Less than I was expecting.
Vance once told me he had .120 removed from his 74.5 for a target CR of 9.6:1
but he did not totally zero deck the block but left it .010 above the pistons
so I guess that would account for some of the difference between .084 and .120
(the more volume between the piston and the top of the block, the more you
have to remove from the head to get the same CR ?)
Stan
From: Derek [mailto:saffrontr@tiscali.co.uk]
Sent: Saturday, January 05, 2008 2:02 AM
To: Foster, Stan
Cc: 6pack (6pack)
Subject: Compression Ratio Calculation
Stan,
Have sent you a seperate email attaching a spreadsheet which details the
various heads fitted to the six cylinder range. According to the spreadsheet
the standard head fitted to the 74.5 is the "219019" and it is 3.5" thick. The
219019 number is stamped onto the top face of the head on the manifold side at
the front of the engine.
Hope that this helps.
Derek
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