A neighbor has a 1987 420 SEL with a problem. She heard a tapping noise on start up and decided to drive her other car. She asked me to have a look which I just did. When I popped the hood I noticed a hole in the drivers side cam cover. Against my better judgement but out of curiosity I started it up. It started quickly and it did tap pretty good but it ran decent for the short time I ran it. I know something in the timing let loose BUT it runs too good for me to believe that it crunched the valves, in fact I've never seen one run after jumping time. I believe the chain is slapping making the noise and hole in the cam cover but it has not jumped time, yet. I have done nothing more than stated here. She said she's not going to fix it and has offered it to me very cheap. You think it would run so well, with excellent oil pressure during the 20 seconds that I ran it, if the timing jumped? I was thinking of buying it, replacing whatever broke [guide/rail/?], new chain, cam cover and driving it.

At idle, it would jump advanced , so wouldn't hurt a valve, sounds like a piece of guide came out (although I've never seen one fracture a valve cover, usually, thats the chain!!).
Other than a pissed off neighbor (once you are driving in her car, after fixing it), what do you have to lose?

Maybe the upper rail broke and somehow did not jump the chain, and then made the hole in the cover.

If there was damage to the valves, you would certainly know it. Sounds like a buy - with a new chain, tensioner, oil tube kits, upper rails and a new valve cover, you're in business.

Just don't start the car again until you find out what's going on.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

Thanks guys! I know I've never seen one run with valve damage. I saw that hole in the cam cover and figured it was all over, having seen it before. I hated to even start it but I figured what the heck and to my amazement it cranked right up but it did rattle pretty good. That's all I've done so far, I haven't removed anything yet. She said she was going to sell it anyway and will not spend any more money on it. It's got over 200k on it but she's spent some money on it including a chain job at 125k, a trans at 180k and various other repairs including the A/C according to the records. I feel a bit guilty buying it for a couple hundred bucks [her offer to me] but I am

I'm off next week so I want to start tearing this apart to see exactly what's going on. I'm going to start with the valve covers to check things out. I hope it's upper guides/rails not anything to deep down requiring pulling the front of the engine off. Is there a link to a online repair manual for specifically the timing chain and components on this 420SEL ? I don't have any books and I'm looking for someting to go by. TIA

Please let us know how it goes. I just had the timing chain and guides replaced on my 90 420 SEL 170,000.