I find a lot of difference in compression gauges, so it matters that you have some experience with YOUR tester. That said I think 140-170 should cover the range of different testers.
Seeing as yours didn't come up much with oil, I expect your ring seal is OK.
I don't understand why you couldn't get the last Cyl. ? the #1, behind the alternator is the hard one. You can get an idea of the one you didn't test by cranking the engine with a spark plug in only a known good cylinder, then again with the plug in only the untested, should sound the same. If it sounds like it is turning over much faster in the untested cyl. It probably has lower compression.
Usually when it has a rough idle but ok at high speeds, it is the valves, as they don't have the time to loose as much at high speed.
Bad ring seal, causes lots of blow-by, oil leaks, etc.
several things con cause rough idle, PCV valve not sealing closed, Idle jet in carb., bad/dirty spark plug, air leak in vac hose/ intake gasket/ decell valve if yours has one.
I would check the valve adjustment, as this is required often, and most people don't do it until a problem arises<g> and these days you have to use an oil additive because they took the zink out of the oil. Without this the valves will close the gap quickly.
Good luck, RGS in Da"Burgh, PA. USA
posted by 151.201.4...
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