Its unlikely the valve springs caused the low compression. It takes very little effort to shut the valves. The springs main purpose is to hold the lifter on the cam lobe. Even a very weak spring will can close a valve at low rpm. Tired springs show up as a miss at medium to high rpm. The weight of the lifter, push rod, and rocker arm is to much for the spring to keep on the cam lobe. As the rpm's increase, the lifter starts jumping off the cam, as it does the valve is held open, thus creating a miss.
A bent pushrod will limit valve lift, so low compression is a result. If you think about how the lifter rides on the cam lobe, it opens and closes as it goes up and down the lobe ramps. With a bent push rod, the length of that push rod is now shorter so the lifter doesn't start to open the valve till higher up on lobe ramp. Not only does not start to open till later, it doesn't open as far, plus it shuts quicker. This short lift cycle means less air for the cylinder and less compression.
You should also be looking for a bent valve or broken piston ring, both can cause little to no compression. Chuck the valves in a drill and spin the slowly looking for a wobble at the stem to head connection.
Go to local parts house and get some valve lapping compound. With a electric drill, you can spin the valves slowly while pulling them up against the seat, the compound will leave a nice dull ring where the two surfaces meet. If the valve is bent, it should leave a gap where no contact was made.
Another easy check after you lap all the valve seats is to assemble the head and poor a thin liquid ( paint thinner ) down the ports and see if the valves are holding. A very small seep is acceptable, drips are not.
A crude spring check can be made using a bathroom scale and wood blocks. The key is to compress each spring the same amount. Take two blocks of wood the same length and place on each side of the scale. If you have a piece of flat heavy steel, place it on the scale to spread out the load. Now place one spring on the scale and lay a 2x4 across it and the blocks of wood. You may need to adjust the hight of the blocks at this point, now stand on the 2x4 and see if you compress the spring. Adjust the hight till you get about 75 lbs of compression. Check each spring and write down your findings. I would expect them all to be close to each other. The is no need to know the springs actual specifications, you are only interested in how they compare to one another. If there is any doubt, new springs are fairly cheap.
