351 Cleveland popping and ticking sound

[jczar]

I need some help. I have a Ford 351 Cleveland. The problem that started my investigation was a popping and ticking sound out of the drivers side exhaust. The popping sound only occurs when I am at steady speed. It does not pop when accelerating or deceleration. I replaced the exhaust header gasket. I cleaned and sealed the exhaust slip pipes. I checked the following: timing @ 34 degrees, vacuum 17 to 18 Hg and holding steady. Checked to see the wires were correct to plugs. Adjusted the air/fuel mix. Checked distributor for cracks and burns. Checked rotor to #1 plug at TDC. Replaced spark plugs. Removed the valve cover and checked the rods. They do not appear bent (spun each one). Checking the compression it seems to have low compression. I squirted oil into #6 and compression came up 4 pounds. The engine starts and runs fine. Added Sea Foam to fuel thinking possible buildup around valves. No vibration, no smoke. Any ideas would be much appreciated.

Compression
#1 = 90 #5 = 92
#2 = 92 #6 = 70
#3 = 100 #7 = 92
#4 = 100 #8 = 90