A few things come to mind for you to check.
Is there a vacuum advance on the distributor and is it hooked up to a vacuum source - should be.
Are the plug wires installed correctly? Firing order is 18436572. Sounds like you have the #1 wire installed correctly. Driver side plugs are 1357 and the passenger side is 2468. The wires on top of the distributor should match 18436572 in a clockwise direction viewed from the top.
If all is correct, re-check the valve lash. Warm the engine and have everything ready to go. Pop the covers off and back off the valves 2 full revolutions. Place the engine at the #1 TDC and check the distributor rotor pointing at the #1 wire. Adust the following valves:

Intake: 1, 2, 5, 7
Exhaust: 1, 3, 4, 8

Rotate the crank one revolution until #6 TDC. Adjust the following valves:

Intake: 3, 4, 6, 8
Exhaust: 2, 5, 6, 7

Finger roll the push rod until zero lash (NO movement) and go one half turn. Once set - leave it alone because the lifter will start to bleed down. If you do then the valves will be open at ignition and causing that popping noise.
Should fix that popping problem.