This is the third installment. Will try to get the photos with the three pieces and make a decent article. There my be a few minor steps I skip in the writeup, because I am assuming an average or better mechanic skill level before you would attempt to change a chain and rails. There may be big steps I skip too, because I am completing each piece from memory after I am cleaned up, not while I am doing the work. M116 engine type in 1985 380SL. 153k miles.
Finished up the job today. I wired up the chain and removed the sprocket on the right cam, after making sure the match marks I had put in earlier were still visible. The tensioner banana rail pin would not come out as advertised. I put an ezout in it, tapped it and turned. Nothing happened. Kept trying, and could not get the pin to budge. Considered pulling the radiator, but the evap would still be in the way. Then I remembered Rusty said the cover was removable. took the new rail and removed and replaced the cover a couple of times. Could it be done with the rail in the engine? It was easy enough to slide off the old cover and pull it out with needlenose. Could not get the new one to hook in at both top and bottom. Then I tried just hooking the bottom, but every time I pushed it down enough to hook the top, the bottom came off. Finally went back to the new rail with the new cover and put in on and off. I found the trick.
Hook the bottom end on the aluminum rail, put a loop of wire around the cover. Pull up on the loop of wire while pushing the op end down into the slot. as the top end slides up, release the wire. Check to see both top and bottom are secured to the rail. Cut the wire and remove it. Now cap the pin. the cover is supposed to have an aluminum seal.
Install the upper rail. Seat all the rail pins after checking all rails again. I used a 5/16 pin punch to seat the pins. On earlier engine s I used to fill the internal threads of the pins with moly grease to protect the threads. You may or may not want to do this. Replace the right cam sprocket onto the cam.
Install the chain replacement tool. Cut the old chain, being careful not to get filings in the chain case. Rags or paper towels around everything also keeps parts of the link or master link from dropping down, a MAJOR problem. I once had to take an engine out and tear it down because i dropped a link, and it wedged in the crank sprocket.
Connect the new chain to the old using the master link. TUrn the crank to roll in the new chain. It takes quite a few revolutions to get the new chain in. In the beginning, you my need to help the old and new chains along, but once it has 10 or 20 links in, both the chains self feed. Remove the master. COnnect the ends of the new chain with the new master link. My new master had 2 tiny c clips in place of the peened link. Nasty little buggers, but they snapped on ok. Check the c cplips very very carefully. This may be the most critical step of the operation. A lost c clip can mean a trashed engine. Remove the chain replacement tool. install a NEW tensioner. I used a piece of 1x4 to pry the tensioner close enough to start the bolts.
turn the engine over slowly to #1 TDC and check the timing marks on the camshafts. If you were able to roll in the chain, you should be ok. Install PS pump plate Install the PS pump and adjust the belt. Install the distributor, but don't tighten the bolt yet. Replace cap and wires. INstall the Alternator bracket. install and adjust the alt. belt.
Replace valve covers. You may want to replace the gaskets. I could not get the left valve cover off the engine. just raised it up enough to clear the cam sprocket. I put a new gasket on the right one. The valve cover bolts are supposed to have aluminum washers. You did order some, didn't you? I didn't because i didn't know they were there.
At this point, I turned the engine over by hand a couple of times then started it. It ran, so I adjusted the dist by ear for fastest idle. I pick a midway point in the travel at the highest speed. You don't want it too advanced or too retarded. Then I shut off the engine and replaced the fan and shroud, radiator hose and vent hose, air cleaner and its hoses, after a genral check of the engine top to make sure I didn't leave any tools there.
I know, y'all need fancy tools to set the dist. But my pappy set the timing by ear, and one of the best mechanics I ever knew did too. Every time I have done it and then had the timing checked, it was right, and didn't need to be adjusted. So now, I just go with it, and don't bother with timing lights and dwell meters, computers, etc.
Loren Faeth
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