450 SL chain replacement - remote starter? - PeachParts Mercedes-Benz Forum

ptspringer · #1 01-11-2009, 04:06 PM

Hi,

I have a 1972, 350 SL 4.5 with 125,000 miles, and just adjusted the valves and checked the "chain stretch". I measured 10 degrees between passenger side cam and the crankshaft. Sounds like it's time for a new chain and tensioner.

So, I'm wondering if I can use a remote starter to turn the engine as I feed in the new chain. I used this for the valve adjustment to rotate the engine by briefly engaging the starter motor, rather than having to remove the fan and clutch and rotate the engine with a socket.

I seems so much easier, yet I've never read it being done. Probably since there is greater risk of skipping a tooth - or worse - if things get out of hand.

Any advice on using (or NOT) the remote starter?

Paul

Strife · #2 01-11-2009, 05:25 PM

I would definitely NOT do this. It isn't a big deal to take off the fan clutch, shroud, and fan (although on an older car, I'd use very good tools and lots of PB blaster, soaked overnight, on the bolts) . Turning the crank with a 27mm (on my car, a short extension, and a breaker bar) was easy with the plugs removed (which you should do anyway). It gives you a great deal of confidence that you didn't do anything grossly wrong when you reassemble the valve train and turn the engine over by hand twice and see everything line up back to zero with no problems or interference. If you DID screw up something, you won't bend anything doing this slowly by hand.

On a car that age, etc, this might be a good time to think about the water pump, too - you are already 1/2 way there in disassembling things.

dkveuro · #3 01-11-2009, 05:29 PM

Quote:

Originally Posted by ptspringer

Hi,

I have a 1972, 350 SL 4.5 ......................

So, I'm wondering if I can use a remote starter to turn the engine as I feed in the new chain.

Paul

How can I put this ? NO !

.

ptspringer · #4 01-11-2009, 06:17 PM

Hey Strife!

Thanks. You said to think about the water pump because I'd be halfway there with my chain. I've been thinking about it, and realized that I'm not sure what to do with it when I'm there.

What do you R&R on the water pump?

So when you're undoing a fan/clutch bolt, how do you keep the fan from spinning?

Breaker bars? Please, you're scaring me!

Is there a lot of force on the cams when installing the chain - would it much rather jump a tooth than turn the cam?

Strife · #5 01-12-2009, 12:19 AM

Well, there's nothing to (r)epair these days, you just (r)eplace it. When is the last time the hoses have been changed? If you value your time, it's easier to replace a lot of things prone to age/mileage related failure "while you are in there".

I use a strap wrench on the fan pulley, or squeeze the belts, to get the fan bolts off.

The breaker bar is only for the convenience of the length, it doesn't take much force to turn the engine (clockwise only, of course) without the plugs.

It really isn't the force, its just that the valve springs lead to uneven slack on the chain and the cams jump forward while you are doing this as the springs snap, and this is how the chain can unexpectedly jump a tooth. This is what makes a job that "seems like it should be easy" tricky, and this is why the manual says to remove the RH rockers (cam followers). A lot of people on this forum don't do this, probably because they don't have the (admittedly expensive) valve compressor. Once you have this, removing the cam followers is extremely easy.

My CFO (wife) assisted me on 3 chain replacements, and lets face it, she was of limited help except for feeding the chain and pulling the old one out. I bought a "gear cover" that fits over the RH cam gear, and this makes it impossible for the RH part of the chain to disengage from the gear, making it almost a one-man job.

I assume that your engine has metal guides (leave 'em), but I would also consider changing the tensioner at this age and mileage. This is very easy during this job; generally, the genuine MB tensioner has been strongly recommended by many (there may be other suppliers for your engine), although it is more expensive.

I would recommend looking over the 107/tech help forums for more information on this subject. There are a lot of "gotchas", like, my 50+ year old eyes needed a custom-made tool and jeweler's loupe to put the e-clips on the master link (after losing a few of them).

dkveuro · #6 01-12-2009, 01:23 AM

http://www.peachparts.com/Wikka/M117TimingChain

wbain5280 · #7 01-12-2009, 04:37 AM

Replace the upper chain guides first then recheck the 'stretch'. If it's still excessive, replace the chain. Check the sprocket tips and if they are sharp and pointed they need to be replaced too. The tips should be flat, almost square.

Tomguy · #8 01-12-2009, 09:45 AM

Quote:

Originally Posted by dkveuro

http://www.peachparts.com/Wikka/M117TimingChain

Exactly what I was going to bring up!

If you follow my guide you can be assured you have done it right. If you use a remote starter you can not keep the old chain and new chain attached to the sprocket because it WILL SPIN TOO FAST causing you to have your clamps fly off, then the chain, then the engine will probably wind up hitting the stopped valve(s) and potentially causing major damage.

Take your time! It's easy and even doing it the "Slow" way you can enjoy a beer or two and have it done in well under 2 hours. If I wasn't taking pictures and writing steps down for the guide it would have taken me an hour tops. I did not replace the tensioner (I did do the rail for it a while back).

ptspringer · #9 01-12-2009, 10:47 AM

Thanks!

You guys are great. And I am going to leave my metal chain guides alone, but replace the tensioner and chain.

TomGuy - Thanks for the tip on beer!

Strife · #10 01-13-2009, 02:01 AM

For this job, I would definitely have the beers AFTER the followers were in and I spun the engine twice, and saw the cams, crank, and distributor all lined up at zero

ptspringer · #11 01-17-2009, 03:52 PM

I completed the chain replacement per Tomguy's instructions.

It was very fun and except for losing the clips for the master link (I bought extras just in case) it went off without a hitch.

The chain had stretched 10 degrees. What a difference in performance!

It was a two Guinness job.

I still have 5 degrees offset, and am hoping that the new chain tensioner I'm installing today will fix that.

Thanks for your help!