Listers,
the comp prep book has all the answers to all your questions. I quote:
<paraindent><param>left</param>the first operation with the cylinder head
is to measure from the combustion chamber face to the valve cover surface
so that the present combustion ration can be determined. The stock
combustion ratio is present if the cylinder head is 3.460" thick. LAter
heads have thicker cylinder heads, ie: up to 3.550" thick.
To acheive acompression ratio of 10.25 it will be necessary to mill
0.085" or 0.175 from the head. tHE HEAD SHOULD NOW BE 3.375" THICK.
This 10.25 C.R. is now correct if zero deck clearance as described
eariler has been carried out. If f you have not established zero deck
clearance, the compression ration will be 10:1.
</paraindent>There. That's it. BTW, the 12.3 number is milling
0.165".
Other points of note:
<paraindent><param>left</param>Average non-decked piston to block height
measure is aprox 0.016".
Head gasket, once torqued, has a cc volume of about 3.7 cc.
Finished chamber volume for 10:1 cr. chamber should be 41.6 cc.
</paraindent>General porting and polishing is required. It took me about
25 hours bit is well worth it.
<paraindent><param>left</param>The sharp edges in the chambers must be
raduised to prevent hot spots.
The intake pors are "horrible" and must be rounded and smoothed and
matched to the intake manifold and gasket. Make a 1.3" template from a
cut down old valve.
</paraindent>For more info just go buy the book. There are some good
photos of what things should look like which do no photocopy well.
While you're spending a week or two of your spare time doing the head
work, why not send out the bottom end for balancing? Buy a header.
Presto, a 125 bhp TR6 (late spec cam and exhaust, were same as the late
PI systems in UK). Much more mid range torque, still idles, a real joy
at 70-80 mph in 4th. Trust me, I've done it several times now.
Dave Terrick
Winnipeg
...someone balance and blueprint my brain please
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