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1980 450sl - My "learn how to work on cars" car
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Hey all,

I am about to change out the spark plugs and wires on my 1980 450SL. I am going to go with the Bosch wires, but I don't know anything about the different types of spark plugs. Can anyone recommend any specific spark plugs, or do they all perform more or less the same?

Thanks!
Zack
 

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'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
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Instead of starting another long discussion here, you might have a look at this thread on the other MB site:

Danger: RESISTOR SPARK PLUGS - ShopForum

What I found, was that our cars (at least the early ones) have plug wires that have a resistor built into the connector at each end. In between, there is just a copper conductor. The plugs that match these wires are non-resistor plugs. Something like Bosch W7DC. But, these non-resistor plugs are getting hard to find from Bosch, so many are using the NGK equivalent.

I bought Bosch wires and have not been able to determine just how they are built, but I do know that they do not have the resistors built in. What it says on the box is not what they are. TheI therefore installed resistor plugs - W7RDC, I think. They seem to be working OK and several mechanics tell me they are doing the same thing.

But, if I was doing this again, I would buy Beru plug wires - they have the resistor ends and buy non-resistor plugs that are equivalent to W7DC or whatever your car was supposed to use. See this link for more info:
ShopForum - View Single Post - Danger: RESISTOR SPARK PLUGS

Good Luck!
 

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After going through the links, from what I can gather, the old style of ignition wire/sparkplug setup has reliability and performance issues, and Bosch has phased them out.

Hence, what I would do in this situation is to rely totally on Bosch to get it right, especially in light of the fact you already bought their wire set.

If you have a technical background, the links are a good read, especially at the Magnecor website.

Plug Wire FAQ

Follow the link, and ensure you got the right wires (part number 09028). As for plugs, I would suggest the Platinum Plus (part number 4020).

http://www.boschautoparts.com/Resources/VehiclePartFinder/
 

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'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
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After going through the links, from what I can gather, the old style of ignition wire/sparkplug setup has reliability and performance issues, and Bosch has phased them out.

Hence, what I would do in this situation is to rely totally on Bosch to get it right, especially in light of the fact you already bought their wire set.

If you have a technical background, the links are a good read, especially at the Magnecor website.

Plug Wire FAQ

Follow the link, and ensure you got the right wires (part number 09028). As for plugs, I would suggest the Platinum Plus (part number 4020).

http://www.boschautoparts.com/Resources/VehiclePartFinder/
If you search the net, you will find dozens of posts suggesting that we stay away from platinum plugs for these cars and just a few in favour. Here is one link:

http://mbca.cartama.net/showthread.php?t=14591

My view is that there is no reason to use anything different from the wires and plugs Mercedes specified, which means use Beru wires and non resistor plugs like W7DC or NGK equivalent. Those resistor wires don't fail - the one link is just trying to sell another product. I changed my OE wires after 35 years just because I thought I should ;) Unfortunately, I bought the Bosch wirees before I did any research - sems OP is going down same path :)
 

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If you search the net, you will find dozens of posts suggesting that we stay away from platinum plugs for these cars and just a few in favour. Here is one link:

http://mbca.cartama.net/showthread.php?t=14591

My view is that there is no reason to use anything different from the wires and plugs Mercedes specified, which means use Beru wires and non resistor plugs like W7DC or NGK equivalent. Those resistor wires don't fail - the one link is just trying to sell another product. I changed my OE wires after 35 years just because I thought I should ;) Unfortunately, I bought the Bosch wirees before I did any research - sems OP is going down same path :)
Thanks for the link.

Just remember, your experience is just one data point.

I just read it, and Bill did not have a technical reason to back himself up as to why someone should avoid Platinum plugs except for the fact that the electrode may fall off. You need to also pay special attention to the design of the Platinum Plus plugs. These are not the Platinum+4's nor the Iridium+4's. And I can understand as to why Bosch didn't recommend them. The Platinum+4's gaps cannot re-gapped and the gaps are quite large.

How many cases have you heard of spark plugs coming apart inside a naturally aspirated engine under normal usage (ie. not racing). And why only for Platinum plugs.

Bill say he was more worried about cheap platinum plugs. Basically, he was back-peddling. Tell me which one is a cheap platinum plug. If you have the technical expertise and the interest, closely examine some of the modern spark plugs as to their design, construction, material, and quality control. Upon looking at the design of the Platinum Plus plugs, I see no reason as to why this plug is prone to self destruction inside the combustion chamber. Also, we are cleared that we are talking about naturally aspirated engines, right?

If you can provide a link where somebody had tried the combination recommended by Bosch and have failed, then it would tweak some interest. For now, Bosch's expertise sounds more comforting than Bill's opinions. As I clearly stated above, you need to change both the wires and plugs at the same time.

If somebody can provide a technical reason as to why these engines are so aversive to platinum plugs and Bosch wires, I would be very thankful. Incidentally, Bosch does offer copper plugs too, but I cannot justify using copper plugs in 2008. It doesn't make sense. Personally, I would use Iridium's but than the OP didn't say he wanted to be a tinker or pioneer.

I used Google a little more, and somebody claims that they found that platinum plugs can get fouled easier (unfortunately he doesn't specify the plug). This I can understand if they didn't changed the wires too. Most spark plugs today are resistor suppressed. In addition, the center electrode is much smaller. If the rest of the ignition system does not compensate, there could be problems. Bosch offers a new wire set and recommends a gap. I don't see an issue.
 
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