Some of these symptoms could be caused from the motor being out of time. Was the timing checked? If that is okay or if you can't tell because it won't run at all, make sure the distributor isn't loose. Meaning the clamp that holds it in position is tight.

If that seems in order then a compression test will tell you a lot. Near equal compression in all 4 cylinders is more important than a high numberin any one or all. A broken valve floating around in a cylinder is going to be obvious. There isn't normally room in there for anything except fumes. A bad reading in any cylinder is more likely a burnt valve, bad valve seats or maybe a broken spring (easily detected by removing the valve cover). Spitting out through the carbs is another hint that there may be a bad intake valve somewhere, although trouble usually comes from the exhaust valves first. Heavy oil consumption can be a sign that your valve stems are not sealing correctly. Heavy damage can occur to the seats if they are still the type that require a coating of lead or a lead substitute to protect them.

Removal of the cover, then the head will give a good visual on the condition of the valves. Things should be clear then. This will also give you a chance to inspect the cylinder walls for any obvious scoring. The head is probably the easiest thing to repair and replace. Damage to the cylinder walls, cam shaft or crank-piston assembly is a much bigger problem.

Oh and just for fun, check the oil at the dipstick to be sure there is no water in it. That will be obvious as water and oil don't mix. Water there means a crack in the block or head somewhere. Not Good.

Any repairs to the head should begin with it being checked for cracks by the shop doing the work. Any new seats installed should be hardened to allow for the use of non leaded gasoline.