I won't use it anymore. Its too easy to get a false reading if anything moves or the cap rocks coming off. I use a ball micrometer and a dial caliper to verify clearances. Its more expensive to go that route so if you're only building one engine its probably not worth it but for me and as anal as I am about stuff like that it was worth it.
This is definately the best way. Just answering the op's questions about the Plastigage.
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