PocketAces said

Was the engine warm when you did the test? Also, did you hold the throttle wide open? Did you crank it enough to build pressure (at least three to four revs)?

I'm no expert, but I think your next step is to squirt some oil into the spark plug hole and see if the compression increases. If it goes up it indicates rings.

You could also perform a leak down test to see if the valves are leaking, but if it were valves (or head gasket) I would not expect the compression to be down evenly in all cylinders. Maybe do a leak down on 2 and 7? On mine I was able to hook my compression tester fitting to a compressed air source and then listen/feel for air escaping from the exhaust pipe (exhaust valve), carb (intake valve) or oil filler cap (rings). You should get some leakage past the rings, so you have to decide if it's excessive.

Do you have an oil pressure gauge, or just a light? It might be worth getting an oil pressure gauge hooked up to confirm you've got good oil pressure.

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SLOPAR72 said

Leakdown test and go from there.... It is odd that all cylinders are down. Whatever the problem is will be abroad. If your leakdown seems OK could it be a valve timing issue? Its strange, i had my timing set at 34 total 18 initial and when i went back to check it 5 months later it was at 44 total and 28 initial, maybe it did skip. It does bounce around a lot with the light around 22-2400.

JW

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Cudafever said

In other words your timing chain may have stretched. Turn the motor over until the time marks line up at 0 then pull your dist cap off, turn the crank in the opposite direction, until the dist rotor just starts to move. look at your harmonic balancer. How many degrees do you have. 16 degrees would be a badly stretched timing chain.

A leak down tester is best. but if you don't have one, a little oil will tell you if it's rings or valves that are leaking.

All three of these things can lower your compression.

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