To check your distributor timing place cylinder #1 at TDC using the notch on the crank set to 0 degrees specified on the timing marker (notch at 12-oclock). Follow spark plug wire from cylinder #1 and #4 and note its location on the distributor. Pull the distributor cap and look to see if the rotor is pointing to cylinder #1 or #4. Pull the valve cover. Whichever cylinder the rotor is pointing to should have the valves closed (firing position), this can be verified by checking the rockers on that cylinder are loose. The other cylinder (#1 or #4) that it is not pointing to should have the valves open (exhaust position), which will have the rockers engaged and tight.
If the rotor is pointing to the cylinder with both valves open, your distributor timing is reversed, the spark is firing with open valves and no compression. If that is the case, remove the distributor, rotate the engine 1 revolution by using the crank pulley nut back to 12-oclock, and reinstall the distributor. Verify the rotor is pointing to a cylinder with closed valves.