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Old 02-12-2002, 02:18 PM
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Join Date: Feb 2002
Location: Minnesota
Posts: 9
Spark Plug Wires for 450SL

I'm a first time poster. I recently acquired a 1976 450SL (my dream car)- the second MB we own. I am doing an overall tune up and I am wondering about the spark plug wires. I changed the plugs and noticed each plug has a rather large metal connector that goes around the plug. Also, the old plugs had the little screw on top removed. My questions are, in replacing the plug wires, do I really need to get ones with these metal boots, or would regular plug wires work. Also, if I replace with the metal booted kind, do I leave the metal screw on the top of each spark plug on, or remove them before I attach the metal boot. Thanks you any assistance you can give. Also, kudos to Phil who has helped me with a lot of parts.
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Old 02-13-2002, 01:08 AM
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well, congrats on owning your dream car. I also couldn't be happier with my Benz. Anyway, about the plug wires. The reason for the metal casing around the plug boot is just a form of insulation. The reason for the little tops of the plugs unscrewed is because thats how the boot fits onto the plug. If that wasn't removed the plug wouldn't stay attached to the wire. If you were wondering about just leaving the little thing on top of the plugs and getting a cheaper set of wires, don't. Take a look at the rotor. Its the same way. As far as i know there aren't any plug wires out there that have the two differnt type of connections at the same time. I believe this is why plug wires for MB are so spendy. I'd spend the money and do it right. Its the safest way to go. Good luck.......

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Old 02-13-2002, 02:03 AM
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Join Date: Aug 2000
Location: Here
Posts: 775
If yours ‘aint broke, then don’t fix it. :)

The metal shield is for EMI reduction; it is a resistor. The failure of one or more of the resistor ends is a common cause of sporadic misfires. You may want to check the ballast resistors while you’re at it.

The ignition systems on these cars are particularly sensitive to the quality of the components. The original plug wires are very long-lived on these cars – this cannot be said of the aftermarket ones.

You can check your existing plug wires for the proper resistance. If you find one or more is not within spec, you can replace the resistor ends individually. (This is assuming that the wire insulation is still in good condition.)

Do not use aftermarket plug wires; even the Bosch ones have not been nearly as reliable as the OEM ones. Beru is the OEM manufacturer. If you’re going to keep this car for a long time, do not skimp on replacement wires.

Two more things. Do not think that you can use resistor type spark plugs as a substitution, it’s not going to work properly. Also, do not be tempted to use platinum plugs – they simply do not work well in that engine. Use the Bosch copper core plugs, preferably with the “O” suffix.


Last edited by RunningTooHot; 02-13-2002 at 02:09 AM.
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Old 02-13-2002, 06:16 AM
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Join Date: Feb 2002
Location: Minnesota
Posts: 9
Spark Plug Wires for 1976 450 SL

Thanks for the reply. The auto store originally sold me platinum plugs. After I read all the negative posts about them I went back and got the recommended plugs. I suspect one cylinder is not firing properly as one of the plugs was fouled - the rest looked fine. I'll try the Beru plug wires and see if it helps. Otherwise she runs fine. Just as a sanity check, the timing on this is supposed to be TDC right? One more question, is there a product to touch up some imperfections on the dash - like where a key chain has rubbed off some of the blue around the ignition key? By the way, did I say it - this is a great site!
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Old 02-13-2002, 11:21 AM
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For your dash - You can pick up a vinyl repair kit for about $10.00. It has a bunch of small containers of raw vinyl in diferent colors. Simply mix the colors you need together to get the right color for your dash. Spread a THIN layer on and put the right graining paper over it and cure with heat . All tools needed are included in the kit. A note to the wise--- if you hurry you will get terrible results. TAKE YOUR TIME - mix color properly and grain it properly and it will be near perfect - only you will know. I have used the kit a few times - the first time I rushed it and was ready to throw the kit away. The second time I really took extra care and patience and was very happy with the results.
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