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Registered
1988 300SEL W126
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555 Posts
Discussion Starter #1 (Edited)
I found this guy on YouTube I don't know if its legit or not, the only way to know ,is to test yourself, I think we will need this method someday, 0 resistance spark plugs are disappearing from the market gradually, BP5ES form NGK are lo longer available also.


 

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Premium Member
87 Euro500HVSEC. 88 Euro 560HVSEC. 89 Euro 560HVSEL
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4,216 Posts
I have seen this before and such a brilliant idea to easily convert any plug to non resistor
I would suggest wearing heat resistant gloves doing that or hold the plug in a socket
 

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SuperModerator
1986/1990 W126
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13,432 Posts
Potentially easier on the EZL, I think there's a quoted spec for the resistance.
So it would depend on what leads you have too.
 

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Premium Member
'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
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10,015 Posts
Interesting to see the plug internals! I would be a bit concerned about that wire inside the plug making good contact.

On the early M117 engines, they used a non-resistor plug. However, the original plug leads had an approx 5kohm resistor on the plug end (as well as a ~1kohm the distributor end). Overall about 6kohm. The new wires used on later models don't have the resistor at plug end and are about 1kohm overall. I therefore didn't see any problem using resistor plugs once I changed to newer wires on my '72. But in theory it makes very little difference to engine performance because current is very low and so therefore is voltage drop. Resistors have more to do with radio/electronics interference.
I have used both types of plugs in my car with 982 M117 engine, and really can't tell any difference.
 

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Outstanding Contributor
350SDL, '17 GLS450, "Grandpa's Roadster" Project Car
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3,033 Posts
Resistance in the HT circuit also shortens the spark duration and extends the life of the plugs.
 

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Registered
1985 MB 500sel (Euro)
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154 Posts
Like MBGraham, I have had both types of plugs and can't tell the difference. Likewise, I still don't understand what that difference is supposed to be and which is better.
 

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Outstanding Contributor
350SDL, '17 GLS450, "Grandpa's Roadster" Project Car
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3,033 Posts
Too much resistance would mean a shorter than intended spark duration and may lead to missfiring.

I suspect the reason the guy uses the torch to loosen the spark plug terminal is because they used loctite when assembling it. I'd suggest, if you go this route, to use red loctite when you put it back together.
 
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