2001 Forester- EJ25 SOHC
Ran fine before I removed the motor for head gaskets, various seal replacement, rear access panel reseal, new spark plugs, etc. Heads surfaced and cleaned, but I did not take the cams out or do anything with the valves. Put it all back together and...had a loud knock from the left head. Drove fine; plenty of power; no issues beside the knock. Put about 30mi on it. Next morning, started up fine (knock still there). Drove it about 1mi and it started to lurch and lose power. Barely made it back home after stalling and restarting with decreased power. Parked it and the catalytic converter was glowing red hot. Today, 3 days later, took off timing belt cover...still timed correctly with belt tight and pullies and tensioner working. Started it...motor quiet without the loud knock, but is now rocking from side to side. Confirmed spark from each plug wire. Removed exhaust from heads and found oil in #3 valve area all other clean; #3 plug very black.
knock
hot CAT
rocking motor
oil in exhaust
Any ideas?