I plug my compression gauge into an air compressor line occasionally to compare its reading to the tank gauge. 80 PSI translates to about a 5.5:1 compression ratio, which is a bit low, but a lot of the time low cranking speed and/or slightly sticky valves can combine to give a somewhat lower than accurate reading.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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