Compression rings use the pressure of combustion to help seal them against the cylinder walls on engines that are actually burning fuel. Pulling a vacuum against a cylinder with a closed intake valve will definitely draw oil past the rings. If the 848 head was originally installed on a Canadian Pontiac 261, it will have the coolant holes drilled into the head to allow the flow of coolant past the siamese-cast cylinder pairs. There will be a total of six holes. The 261 head gasket is also different than the 235 because of the 3 3/4" bore size.
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
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