I recently parked my 1985 500 sec in my garage to perform a few maintenance and repair tasks. One was the Tranny B2 piston and the other was to replace the oil filter housing check valve which I suspected was the cause of my delay in getting oil pressure on startup. After performing both of these and several other minor repairs, I just decided to drop the lower oil pan to have a look-see! OH MY GOD I COULDN'T BELIEVE MY EYES! There were the remains of TWO timing chain guide rails laying in the pan and pieces were completely clogging up the oil pump suction screen. It is a pure miricle that this didn't damage my engine. What is strange is that about 3 months ago I replaced the timing chain and tensioner via the clamp/masterlink method. The upper guide rails were absolutely fine as could be seen from above. At this time I decided to skip the guide rail replacement and in fact didn't even bother to drop the lower oil pan and look at the lower rails. So my UPPER rails were good but my LOWER rails are disentigrated. Now I am in the process of tearing he front of the engine apart to replace ALL of the rails. This appears to be a pretty major task and if anyone has ever removed the timing cover on a 117 series engine, I could probably use some pointers if you could please. I have the CD-ROM repair disc and the Chiltons but really need to know some helpful hints or pointers before I get started. Thanks a Great deal, Brant