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Having a real tough time with my 71 Nova and need some help. Have a rattle coming from both back cylinders and wont run like it used to, smooth and fast. Now it acts off balance and rattles like its off timing or missing, but not. When I floor it the engine doesn't backfire through carb but just misses. I must mention when I first started if after sitting several months I got a bad metal on metal noise for a few seconds. Stopped cranking it, waited in fear, and tried again. Started right up but now this problem. What I have done to try and render my ailing car.
-rebuilt Edelbrock 1406 carb with fresh rebuild kit - found no real issues.
-rebuilt Flamethrower distributer, cap, internal cap, new module, wires, plugs, but kept coil. Cap was worn along module from 2006.
-Took to local crappy garage who I thought they would be helpful, wrong. Told me carb was internally leaking (BS, hence the rebuild) and that #7 cylinder was not fully firing. Compression on all cylinders good and timing was on along with all spark plugs firing. They removed drivers side valve cover to check rocker arms and push rods. all seems good.

SO, I got it to run a little better with all my improvements but it still rattles and still is not running smooth. No smoke or smell of gas. I again removed the drivers side valve cover to check and yes all push rods are moving up and down with rocker arms cannot find any real play in valves or equipment. Rods are tight. I did notice one push rod on #7 is spinning. Read that's normal.

I have removed the ignition wire from the back cylinders but barely change in rattle but does run rougher when done.

Any other tests I can do to determine what's wrong?
If cam damaged why would the valves appear to still be moving the same amount as the others!??
Lifters damaged?

If a crank bearing is damaged would that cause these rough running issues or would that be a different type of noise? No noise from under the car just above around rear valves area.

Rods look straight along with springs and seats.
It has a double link timing chain from 06 installed along with high flow water pump.

Any help appreciated. thank you.
 
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