The "887" and the "913" heads both have the same bolt pattern as the "848"- - - -the difference is the compression ratio. Either of the earlier heads can be brought up to 848 compression specification by milling 3/32" (.090") off the head gasket surface, but the intake valves also need to be recessed the same distance to protect the edge of the valves from the flame front as it travels across the top of the pistons. Correct the rocker arm geometry by putting 3/32" shims under the rocker shaft stands, and 11/32" diameter lash caps on top of the exhaust valve stems.

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Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!