Author Topic: Spark plugs - resistor plugs  (Read 1834 times)

ghebert4189

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Spark plugs - resistor plugs
« on: July 24, 2022, 19:09:01 »
Good morning,
I'm looking for any insite on spark plugs for a 1971 280 SL. My mechanic recommends using non resistor spark plugs, but I am having real hard time finding any. Is anyone using the resistor plugs in their 280 SL's, and if so are you having any issues? Also, can you mic plugs with some being resistor and some the old solid state? Lastly - anyone know where I can get some of the solid state plugs?

Cees Klumper

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Re: Spark plugs - resistor plugs
« Reply #1 on: July 24, 2022, 20:39:33 »
NGK BP7ES would be a good start as far as heat range, available from various suppliers. These are non-resistor.
Cees Klumper
1969 Mercedes 280 SL automatic
1968 Ford Mustang 302 V8
1961 Alfa Romeo Giulietta Sprint Coupe 1600
1962 FIAT 1500S OSCA convertible
1972 Lancia Fulvia Coupe 1.3
1983 Porsche 944 2.5
1990 Ford Bronco II

Benz Dr.

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Re: Spark plugs - resistor plugs
« Reply #2 on: July 24, 2022, 23:25:09 »
NGK BP7ES would be a good start as far as heat range, available from various suppliers. These are non-resistor.

I used to use BP5ES but they're no longer available through my normal sources. We found some AC plugs that are non resistor so will see how they work. Resistor plugs have at least 5K ohms of resistance which you don't need.
1966 230SL 5 speed, LSD, header pipes, 300SE distributor, ported, polished and balanced, AKA  ''The Red Rocket ''
Dan Caron's SL Barn

1970  3.5 Coupe
1961  190SL
1985   300CD  Turbo Coupe
1981  300SD
2013  GMC  Sierra
1965  230SL
1967 250SL
1970 280SL
1988 560SEC

ja17

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Re: Spark plugs - resistor plugs
« Reply #3 on: July 25, 2022, 13:43:19 »
Finding non-resistor plugs is becoming a real problem these days. I heard that Bosch began suppling them again, special order, but are very expensive ($12.00 ea.?) from Mercedes. You use a MB part number and order at the dealer. Otherwise, if you had an old original non-transistorized ignition and upgraded your ignition to a hotter coil and ballast resistor, your probably fine with a resistor spark plug. It's best to use non-resistor if possible. I also heard that the old Champion 7YC, non-resistor, copper core plug is still available?
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
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1965 220SE Finback

mdsalemi

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Re: Spark plugs - resistor plugs
« Reply #4 on: July 25, 2022, 14:02:16 »
Good morning,
I'm looking for any insite on spark plugs for a 1971 280 SL. My mechanic recommends using non resistor spark plugs, but I am having real hard time finding any. Is anyone using the resistor plugs in their 280 SL's, and if so are you having any issues? Also, can you mic plugs with some being resistor and some the old solid state? Lastly - anyone know where I can get some of the solid state plugs?

I use BP6ES and when they started becoming scarce last year, bought up a lifetime supply from all the local suppliers. I would NOT mix resistor/non-resistor...
You can probably find some non-resistor on eBay...
Michael Salemi
Davidson, North Carolina (Charlotte Area) USA
1969 280SL (USA-Spec)
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zoegrlh

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Re: Spark plugs - resistor plugs
« Reply #5 on: July 26, 2022, 19:52:13 »
I did the same as Michael, bough up all the Bosch plugs I could find when they stopped making them. However now I am running NGKs, as Joe suggested and put in for me at the PUB Virginia. They run really smooth, I’m sold on them, but still have the Bosch in safe keeping.
Robert Hyatt
Williamsburg, VA.

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franjo_66

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Re: Spark plugs - resistor plugs
« Reply #6 on: July 27, 2022, 00:29:48 »
there are still NGK BP5ES available if you scour ebay and vendor sites. I bought 50 of them from rockauto.com as they are also used in my 560SEC and BMW E23 735i

I personally think the BP7ES are a bit too "cold" for our engines.
Franjo

1965 230SL Black/Auto/RHD
2005 Porsche Cayenne Turbo
1983 BMW 735i
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1991 500SL
1982 Holden Statesman DeVille

Benz Dr.

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Re: Spark plugs - resistor plugs
« Reply #7 on: July 27, 2022, 00:56:01 »
there are still NGK BP5ES available if you scour ebay and vendor sites. I bought 50 of them from rockauto.com as they are also used in my 560SEC and BMW E23 735i

I personally think the BP7ES are a bit too "cold" for our engines.

They are, although it's what's called for.
1966 230SL 5 speed, LSD, header pipes, 300SE distributor, ported, polished and balanced, AKA  ''The Red Rocket ''
Dan Caron's SL Barn

1970  3.5 Coupe
1961  190SL
1985   300CD  Turbo Coupe
1981  300SD
2013  GMC  Sierra
1965  230SL
1967 250SL
1970 280SL
1988 560SEC

Cees Klumper

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Re: Spark plugs - resistor plugs
« Reply #8 on: July 27, 2022, 07:05:37 »
Motivated by this thread I checked the condition of my BP6ES plugs yesterday, and noted that they were getting too hot. So I am ordering BP7ES to try. Very plentifully available here in France on Amazon.
Will also check ignition timing (although that should be spot on) as incorrect timing can also cause plugs to run too hot. I don't think it's running lean, judging from my 19 MPG consumption.
Cees Klumper
1969 Mercedes 280 SL automatic
1968 Ford Mustang 302 V8
1961 Alfa Romeo Giulietta Sprint Coupe 1600
1962 FIAT 1500S OSCA convertible
1972 Lancia Fulvia Coupe 1.3
1983 Porsche 944 2.5
1990 Ford Bronco II

neelyrc

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Re: Spark plugs - resistor plugs
« Reply #9 on: July 27, 2022, 13:35:03 »
On NKG.com they indicate that the 7832 BP5ES has been discontinued which we have known for some time.  They recommend NKG 7734 BPR5ES as a replacement.  Has anyone tried these plugs.

I see limited numbers of 7832 plugs still offered on the internet in Italy but at extremely high prices.
Ralph

1969 280SL, 4 Speed Manual, Dark Olive (291H), Parchment Leather (256), Dark Green Soft Top (747)
1972 Mercedes-Benz 280SEL 4.5
1988 Mercedes-Benz 560SL
2007 BMW 328xi (E90)
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badali

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Re: Spark plugs - resistor plugs
« Reply #10 on: July 27, 2022, 14:02:55 »
W7DC are available now.  Just do an internet search.  They are about $3 each depending where you buy them...
Brad

1961 220 Sb
1966 230 SL
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Vander

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Re: Spark plugs - resistor plugs
« Reply #11 on: July 27, 2022, 14:42:09 »
On NKG.com they indicate that the 7832 BP5ES has been discontinued which we have known for some time.  They recommend NKG 7734 BPR5ES as a replacement.  Has anyone tried these plugs.

I see limited numbers of 7832 plugs still offered on the internet in Italy but at extremely high prices.

Do not use those, the 'R' in them signifies resistance.
1969 280SL