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Yes you are correct The service manual focuses on how well the motor compresses during the first four strokes. If compression jumps up "quickly" it indicates good pressure. If it is slow to come up...

Yes the 20 times number is high. The thought being if you are getting that high of pressure, the cam timing is either very short or, off.

Thanks for the kudos! Good luck on your endeavor.

67 Kaiser, there is an old engineering rule of thumb for cranking compression. It should be 15 to 20 times the compresion ratio. I don't know if you can find the ratio however. That is a pretty good...

67 Kaiser, You didn't mention how low but, most engines running on gas wont fire when cranking pressure drops much below 70psi. The real check is a leak down. More than 10% indicates valves or rings....