A customer recently showed up to the shop with a check engine light on his Taurus SHO. Very nice car by the way even with the 90K miles on it. He complained that it ran a bit rough for the last month or so, with diminishing fuel mileage and a glowing yellow light. Upon running the codes, we discovered he had a code that stated Bank 2 over-retarded. After checking the VCT error pids, I determined that Bank two did not respond to VCT commands and showed it was off by 33 degrees...
I priced him out to tear the front of the engine down and see what was going on. Likely would need timing chains, tensioners, the works. He figured it would be safe to drive for now since it's been doing this for the last few weeks at least.
A few moons later, the car was towed in for a no start. You go out there and push the button (push button start) and she spins over with no resistance what-so-ever. I rip the front valve cover off, verify which cylinder has valves closed, and sock air into the cylinder with a leak down tester. Awesome tool; If you don't have one, I highly recommend getting one. The leak down tester showed an amazing 70% leakage and I could hear the air rushing straight out of the intake. Looks like it bent the intake valves.. now was the time to sell them the labor to tear the heads off.
To get the heads off, you drop the sub-frame right out of the car with the transmission, axles, and struts still attached. It was pretty easy work. A work buddy always jokingly says "cab off" for every repair, but this basically fits that description. I attached a picture showing the timing chain tensioner completely maxed out and the guide positioned too far over. When comparing the old chain and the new chain side by side, it looks as if the old chain had gained almost 2 full links.
You should not rotate these engines backwards in any case, but of course I decided to try it with this engine. Rotating it backwards put force on the tensioner, retracting it, causing major chain looseness in my situation. So much looseness, that the cams would not turn and the chain would skip right over the teeth on the crank. I am assuming that the chain jumped time when the engine was turned off, likely kicking back as it showed down and fought cylinder compression.
Once the heads were removed, you could clearly see where all the intake valves kissed the pistons. Upon removing the valves, all the intake valves were bent. It appears as the the pistons were ok, the cylinder heads and valve seats were ok. The customer opted to go the cheaper route (since it was customer pay) so we just lapped in new intake valves and threw it back together with new gaskets.