My son has A 70 396. Gave it a compression check, two cylinders were 90, the rest were 130. Put some oil in the 2 low ones, and no change. He had put on a complete set rebuilt heads on a few years ago, because compression was low. The old heads you could see light through the seats. So he thought that was his problem then. The car actually does not run bad, and is not burning oil.Any ideas? Also when he put the new heads on, he also replaced the cam. Thanks

Sounds like the rings are worn. If it runs decent and he isn't concerned about maximum performance, I would leave it alone. Seems once you get into an engine, the work and money never stop. It doesn't work well to just replace rings. You will get into boring oversize and new pistons and then as long as it's out, maybe a little more compression and hey, the rectangle port heads breath better, so let's get those and now I need a bigger cam and may as well go roller, so we need roller lifters and might as well get roller rockers and that new aluminum intake will be better and that 950 demon carb should feed this beast, oh and new 2 1/8 primary coated headers to get it all out and the 3" exhaust etc. etc. etc...... :p

Until it starts smoking noticably or running rough, just drive it..... ;)

I aggree. It is probably rings.
If your oil rings are doing their job, but the compression rings are a little worn, it won't burn oil, but it will loose compression. Usually if the compression rings are worn though, it will allow vacume to suck oil around the oil ring and it will burn oil.
It should have made some diffeence when you put the oil in the cyll checking compression. Are you sure you put enough in? Did you crank it over once or twice after adding oil?

I aggree with S_c_SS. Just drive it.

I suspect valves since putting oil in made no difference.