I recently bought an 08 charger RT with 81k miles. I've put about 1k miles on it since the purchase. I drove to work with no problems, left about an hour later and the charger cranked up and missed pretty bad. This had happened one other time but quickly went away, so I went ahead and drove home. The miss didn't go away. Did a compression test to see if I had dropped a valve seat, 0 compression on #6. Popped the valve cover, everything looks fine at first glance. Hooked up the compressor to #6, exhaust valve is leaking, everything else seems fine. I got a flex cam and looked in the combustion chamber... Everything looks fine.. no scratches, valve looks normal, no metal pieces. I am confused. I can't see any breaks in the spring and the heads were replaced right before I bought it. New springs, pushrods, valves, and new pistons. Any help or advice would be appreciated, thanks

 

Roll the motor over slowly, and watch the valve train, are both valves opening/closing when they should?

 

They appear to be opening and closing properly. I pulled the covers and let the engine run for a few seconds at first and couldn't see anything wrong. I ran a compression test and leak test after that. I still haven't been able to find a problem. The spring looks fine, I even tried pulling/prying up a little while I had the air compressor on to try to seal the valve. No luck. Made a valve spring tool and can't get the spring retainers to break loose to get the spring off. Tried nylon rope, no luck, looks like I'm going to have to pull the head. Really didn't want to though