Hello all, just recently starting having trouble with my 66 289. the engine was rebuilt 20,000 miles ago as far as I know. the engine was missing and after replacing all the plugs and wires and resetting the points and timing I found the upper plate of the distributor does not seem to sit tight against the bottom plate thus constantly changing the gap of the points. worn out I guess, but maybe just a cruddy design from what I have heard. well after all that and no change in symptoms I decided to do a compression test. I found cylinder 4 had 0 lbs of compression and cylinder 5 had 5 lbs of compression with all other cylinders checking 110 - 118. well cylinder 4 was open shut case because the intake valve spring was busted. but cylinder 5 looks like its burning clean just like the other 6. I tested the valve springs on cylinder 5 and they were in spec. valve guides are fine. the exhaust valve did have a little bit of striations on half of the valve seat which might indicate leaking and a bent valve but I don't see this reducing the compression to 5 lbs, I could be wrong. I replaced all the valve stem seals because they came with the head gasket kit, even though the old ones still had some life left in them. also I am pretty sure the valves are not the harden kind because the seats have little dents probably from carbon being sandwiched between the valve and the seat so perhaps I should change over to the harder valves, I don't know what do you think? before I put the heads back on I was looking for any advise you all could give me about what else to check, ( lifters, cam shaft, piston rings?) also I was going to use a chiltons manual to adjust the valves, it is the later 66 engine which has the notched rocker arms, the manual says with the piston at top of the stroke tighten the nut until the push rod has no play in it, I assume this means you tighten it until just the free play is gone not until the push rod is tight because it seems like the pushrod never gets tight due to the hydraulic lifters right?