Author Topic: spark plug question (Read 36905 times)

merrill · « **on:** October 21, 2006, 11:27:38 »

hello all,
just purchased new red coil, points, condenser and 1.8 ohm ballast from cheryl at K&K.

can I use the current spark plugs in the sl.. bosch plugs MB part # 002-159-24-03
which cross references as bosch WR7DC+

I replaced all the components as I could not id the coil or ballast due to corrosion. ballast ohm'd at 1.8 ohms

matt

Matt
66 230 sl - "white"
78 300 D - Blue
98 C230

Naj ✝︎ · « **Reply #1 on:** October 21, 2006, 13:18:13 »

Matt,
I would avoid the "R" resistor type plug.

I use Bosch W8DC

naj

68 280SL

mdsalemi · « **Reply #2 on:** October 21, 2006, 15:33:44 »

Resistance NEEDS to be in the equation SOMEWHERE if you want to listen to a radio. That one place it needs to be is in the connectors, or the wire, or the plugs--but only in one of those places.

If you use typical German Bosch or Beru plug connectors, there's your resistance--you don't need any more.

If you have a "stock" or like stock wire set, it is solid copper, so you need the resistance in the caps or plugs, and typically it is in the connectors.

Resistor wire is common aftermarket stuff but breaks down far easier and faster then copper. If you use those proper connectors you do not need or want resistor wire.

I think someone invented resistor plugs to avoid the use of troublesome resistor wire, and on domestic cars that don't have resistor connectors.

Bottom line--you want resistance in ONE place only...

Michael Salemi
1969 280SL
Signal Red w/Black Leather
Restored

merrill · « **Reply #3 on:** October 21, 2006, 17:36:34 »

Michael,
so, here is exactly what I have

bosch spark plug wires, on the wire it says 7mm silicon high temp
the ends read, bosch germany, k4, 0356 30 1022 1k ohm

spark plugs, read bosch super ro 085 then above the threads w7dc

is this a good combinatio with the
red coil, 1.8 ohm resister?

matt

Matt
66 230 sl - "white"
78 300 D - Blue
98 C230

ja17 · « **Reply #4 on:** October 22, 2006, 06:33:46 »

Hello Matt,

Non resistor spark plugs are getting hard to find. Some manufacturers are phasing them out all together.

The original plug wires are solid copper with a silver colored coating (tin most likely). The ends on these wire sets can be screwed off and changed if they become bad. The wires themselves never fail unless the insulation jacket is damaged or becomes bad. You can replace the wires themselves by buying it in bulk and screwing on the original ends. These original ends should be checked with an ohm meter at every tune -up. The early plastic ends #000159 2185 had 1,000 ohm resistance. The later metal ends #000 156 3210 (used with the factory electronic ignition) had 5,000 ohm resistance. The solid copper wire could be bought from Mercedes by the foot #110 159 1818, but probably cheaper at your local hot rod, tractor or motorcycle shop in bulk. The wire ends at the distributor also had removable ends with a set resistance (1,000 ohms I believe). The manual suggests replacing defective parts when the total resistance on each wire reaches 20,000 ohms resistance.

I simply check the wire set with an ohm meter and replace any component which is radically lower than the others.

Now all this information is great if you have the original coil, ballast resistor and original wire set or similar.

Basically what you want to avoid is the resistance carbon wires used on most other vehicles. These will fail.

Resistance spark plugs may not cause you a problem, but the danger is that you will be adding too much resistance to the system causing weak spark of premature failure of some other component. It all depends what wire set you are using, and which coil ballast resistor etc are installed. Non resistor spark plugs are specified for these cars for this reason.

If finding non resistor Bosch plugs becomes difficult, there are other alternatives. NGK spark plugs were originally designed for the high performance motorcycle crowd. They still produce the BP6ES (non resistor spark plug) which work well in the pagoda engine.

Here are some original version spark plug connectors,

Download Attachment:

spark plug wires.JPG
54.92 KB

The right angle version was used only on #1 cylinder of Mercedes sedan carbureted engines.

Joe Alexander
Blacklick, Ohio

merrill · « **Reply #5 on:** October 22, 2006, 09:40:37 »

joe,
thanks for the reply, so, I guess, the name of the game is to not have more than 20,000 ohms resistance. does this include the spark plugs?

I am assuming this is from the distributor end of the wire to the spark plug end?

matt

Matt
66 230 sl - "white"
78 300 D - Blue
98 C230

ja17 · « **Reply #6 on:** October 22, 2006, 21:29:54 »

Hello Matt,

Yes if you have to use resistor type plugs you should also count the resistance of the spark plug.

Yes I like to check from the contacts in the distributor cap and on through the spark plug connector with non resistor spark plugs.

Joe Alexander
Blacklick, Ohio

hands_aus · « **Reply #7 on:** October 23, 2006, 21:52:05 »

quote:
Originally posted by ja17

Hello Matt,

Non resistor spark plugs are getting hard to find. Some manufacturers are phasing them out all together.

The original plug wires are solid copper with a silver colored coating (tin most likely). The ends on these wire sets can be screwed off and changed if they become bad. The wires themselves never fail unless the insulation jacket is damaged or becomes bad. You can replace the wires themselves by buying it in bulk and screwing on the original ends. These original ends should be checked with an ohm meter at every tune -up. The early plastic ends #000159 2185 had 1,000 ohm resistance. The later metal ends #000 156 3210 (used with the factory electronic ignition) had 5,000 ohm resistance. The solid copper wire could be bought from Mercedes by the foot #110 159 1818, but probably cheaper at your local hot rod, tractor or motorcycle shop in bulk. The wire ends at the distributor also had removable ends with a set resistance (1,000 ohms I believe). The manual suggests replacing defective parts when the total resistance on each wire reaches 20,000 ohms resistance.

I simply check the wire set with an ohm meter and replace any component which is radically lower than the others.

Now all this information is great if you have the original coil, ballast resistor and original wire set or similar.

Basically what you want to avoid is the resistance carbon wires used on most other vehicles. These will fail.

Resistance spark plugs may not cause you a problem, but the danger is that you will be adding too much resistance to the system causing weak spark of premature failure of some other component. It all depends what wire set you are using, and which coil ballast resistor etc are installed. Non resistor spark plugs are specified for these cars for this reason.

If finding non resistor Bosch plugs becomes difficult, there are other alternatives. NGK spark plugs were originally designed for the high performance motorcycle crowd. They still produce the BP6ES (non resistor spark plug) which work well in the pagoda engine.

Here are some original version spark plug connectors,

Download Attachment: spark plug wires.JPG
54.92 KB

The right angle version was used only on #1 cylinder of Mercedes sedan carbureted engines.

Joe Alexander
Blacklick, Ohio

Hello Joe A,
Are the spark plug wires/connectors supposed to have the small rubber boots on both ends?
My 250sl has them only on the distributor end.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

ja17 · « **Reply #8 on:** October 24, 2006, 05:15:23 »

Hello Bob,

I can't say for sure that all years had the rubber boots on the plastic spark plug connectors. The late BBB (07-12/1) does show the rubber boots on the plastic spark plug connectors.

Joe Alexander
Blacklick, Ohio

hands_aus · « **Reply #9 on:** October 25, 2006, 05:48:39 »

quote:
Originally posted by ja17

Hello Bob,

I can't say for sure that all years had the rubber boots on the plastic spark plug connectors. The late BBB (07-12/1) does show the rubber boots on the plastic spark plug connectors.

Joe Alexander
Blacklick, Ohio

Hey Joe A

Thanks for the info, I will look in my BBB.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

Benz Dr. · « **Reply #10 on:** October 25, 2006, 10:28:01 »

I use W9DC unless the engine has full compression and then I'd go to the colder W7DC. On the 90 degree distributor cap ends used on 280SL's the resistance is about 1K and the metal ends should be 1K not 5K. The rotor has 5K built into it so you need to consider that also. Any plug wire that has 20K of total resistance is beyond junk and I can't imagine why the BBB would even state such useless informatin.
Modern Bosch spark plug wire is stainless steel and not copper wire.

Dan Caron's
SL Barn
benzbarn@ebtech.net
slbarn.mbz.org
1 877 661 6061

ja17 · « **Reply #11 on:** October 25, 2006, 18:25:55 »

Hello,
Maybe modern replacement sets have those specs, however the originals were 5,000 ohm for the metal shielded spark plug connectors and 1,000 ohms for the plastic spark plug connectors. Maybe new replacement sets are stainless wire but originals spark plug wires were definately coated solid stranded copper wire.

Download Attachment:

wire ends.jpg
61.53 KB

A page from Mercedes Benz Technical Training Manual also gives these specifications in Feb, 1967

Supressed Spark Plugs 5,000 ohms
Original Coil 1.7 to 2.1 primary resistance
condensor capacity 0.23 to 0.32 MCDF
distributor rotor 5,000 ohm
unshielded spark plug connectors 1,000 ohms
metal shielded spark plug connectors 5,000 ohms
coil wire end at coil 1,000 ohms
coil wire end at distributor 1,000 ohms

Joe Alexander
Blacklick, Ohio

Benz Dr. · « **Reply #12 on:** October 26, 2006, 16:08:12 »

Your info is correct. I disagree with the original metal ends being 5K. All ones I've ever seen were 1K but that doesn't they weren't changed.
I did say that modern wire is stainless. No mention from me about original stuff. Good to know these things and I think we would all agree to keep carbon core out of the mix.

Dan Caron's
SL Barn
benzbarn@ebtech.net
slbarn.mbz.org
1 877 661 6061

ja17 · « **Reply #13 on:** October 26, 2006, 21:17:12 »

Hello,

Yes, no carbon wires! I just pulled a set off an old Mercedes 4.5 sedan. You could feel and hear the carbon crackling and popping as you flexed the wires, hundreds of little short circuits!

Joe Alexander
Blacklick, Ohio

hands_aus · « **Reply #14 on:** October 27, 2006, 04:32:38 »

I saw a comment on the ozbenzforum that Bosch has stopped making non-resistor plugs
http://forum.mbspares.com.au/viewtopic.php?t=445
does that mean I should be squirreling away sets of plugs for my car? currently using W7DC set at .040" gap.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

Vince Canepa · « **Reply #15 on:** October 27, 2006, 05:41:09 »

My car has the original metal ends and they are 5K. Maybe that is because mine has the radio supression option (code 533). I know this is a sore point for Dan, but mine has never had starting ot idling problems.

The wire was "tinned" copper originally. The little brass contacts that were used with the straight ends at the coil and distributor were soldered. That doesn't work with the stainless wires.

Vince Canepa
1967 250SL
113.043-10-001543
568H Signal Red
116 Caviar MB-Tex

mdsalemi · « **Reply #16 on:** October 27, 2006, 06:44:05 »

quote:
Originally posted by hands_aus

I saw a comment on the ozbenzforum that Bosch has stopped making non-resistor plugs
http://forum.mbspares.com.au/viewtopic.php?t=445
does that mean I should be squirreling away sets of plugs for my car? currently using W7DC set at .040" gap.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

It means you should squirrel away set only if you want them. I've heard from many sources that NGK's are less apt to foul...My NGK's do seem to burn a bit better, and using the stock recommendation of BP6ES. My Bosch's (I've had both in and out over the past couple of years)seem to get a bit blacker, meaning more fouling.

Important to note that even when new (read the reports from yesteryear in the Gold Portfolio book)thess cars ran rich and tended to foul plugs.

All that being said, I can't for certain say my car runs "better" with NGK's then with Bosch, it's just the post-mortem analysis shows cleaner plugs with NGK and that's it.

Michael Salemi
1969 280SL
Signal Red w/Black Leather
Restored

Vince Canepa · « **Reply #17 on:** October 27, 2006, 10:06:16 »

I have used NGK B7ES for years. I never really liked the "projected" tip plugs (the "P" in BP6ES or BP7ES). It's a matter of personal preference really, but I think the NGKs do run a bit better in these engines. Regarding fouling, back in the days of leaded fuel, the lead would form deposits on the tips of the plugs causing a high speed miss as miles accumulated on the plugs. A good run at high RPM would usually clear the plugs. NGKs seemed a bit less prone to the fouling. The problem disappeared with the debut of unleaded fuels.

Vince Canepa
1967 250SL
113.043-10-001543
568H Signal Red
116 Caviar MB-Tex

al_lieffring · « **Reply #18 on:** October 27, 2006, 16:11:10 »

Our shop always used Champion plugs, the Bosch plugs made in the 70's would break off just below the hexagon leaving the threads stuck in the cylinder head. I had to chizzel hundreds of them out.
Back then the Champinion application charts showed N7Y for fuel injected 6's, N8Y for carbureted motors, the N9Y for 3.5 and 4.5 V8s and N12Y for the 6.3 V8.
7 being the coldest, 12 the hottest.
Later a copper core was added and the letter C.

I ordered a dozen N9YC plugs and are running them in my motor now. Champion shows the RN9YC resistor plug as the correct aplication and the non resistor N9YC is still available but shows up as a small engine and motorcycle plug.

Leaded primium gas was still around the last time I drove this car, and the colder 7 heat range was to reduce the lead fowling, That shouldnt be a problem now so I am running the hotter 9's to keep down carbon build up.

Al

113-042-10-014715
built 11 Jan 66
904/396 blue, Ivory Tex
condition- rust bucket

ja17 · « **Reply #19 on:** October 27, 2006, 17:57:21 »

Hello,

Well I started off using Bosch spark plugs back in 1966 in my 190SL. Back then I used to get them from JC Whitney for twenty nine or thirty nine cents each. The Bosch plug at the time was the W175T30 for most Mercedes four and sixes.

I used Champions N7Y and these Bosch plugs in my shop until the introduction of the copper core plug. A customer (Pat with the Tobacco Brown 280SL on this list) introduced me to the NGK plug in the early 70's. It seems the copper core NGK plug become popular first for the high performance Japanese motorcycle crowd. Pat's 280SL ran a bit lean actually and would only stay running good if NGK plugs were installed. After several failed attempts at tuning with old series Champion and Bosch plugs in his 280SL, I gave in and installed the NGK's. The high speed miss disappeared and did not return. Several years later Champion came out with their copper core plugs N7YC etc. These were obviously superior to the non copper core Bosch at the time (W175T30). I also had experience with these old series Bosch plugs breaking off an leaving the threaded ends in the engine on occasions. It seemed that Bosch was the last to introduce their copper core plugs (supper series) a couple of years later. These were much improved and at least comparable with the other copper core plugs of Champion and NGK.

I like the nickel coating on the modern Bosch threads the most. The modern Bosch plugs seem the least likely to seize or gauld if left in the engine for years. The plating on the threads of the Champions (zinc possibly) seems less resistant to this. The NGKs between the two as far as resistance to this.

I still lean toward the NGKs in my own vehicles for performance but will not hesitate to use the non-resistor Bosch if needed.

Joe Alexander
Blacklick, Ohio

J. Huber · « **Reply #20 on:** October 27, 2006, 20:55:23 »

Not sure why -- but my mechanic put in NGK BP5ES last tune-up. That was March '03 -- a little over 15,000 KMs ago. Car has run really well.

James
63 230SL

merrill · « **Reply #21 on:** November 06, 2006, 18:53:05 »

Joe,
so took some time and found the following

cylinder ohm in 1,000's (wire and end) meter in 20 K ohm range
1 5.09 - had 5k ohm end, the rest had 1 k ohm end
2 1.29
3 1.26
4 1.24
5 1.23
6 1.23

rotor 5.09
wire from coil to distro center 13.46

so, no wonder why I had a miss, when the wire ends were mis matched
Ordered new wired and plugs from cheryl at k and k today.

BBB data from joe
Supressed Spark Plugs 5,000 ohms
Original Coil 1.7 to 2.1 primary resistance
condensor capacity 0.23 to 0.32 MCDF
distributor rotor 5,000 ohm
unshielded spark plug connectors 1,000 ohms
metal shielded spark plug connectors 5,000 ohms
coil wire end at coil 1,000 ohms
coil wire end at distributor 1,000 ohms

Matt
66 230 sl - "white"
78 300 D - Blue
98 C230

mdsalemi · « **Reply #22 on:** November 06, 2006, 19:54:25 »

Hi Matt,

I don't want to disillusion you, but been there and done that. You didn't have a mismatched end; you in all likelyhood had a newer style, boxed set of wires from Bosch aftermarket. These, in the W113 spec (I'm sure it fits a whole bunch of 6 cylinder cars) have the #1 wire with a 5K connector on it. It's angled, too, not straight like the others.

I still have my set, and I can tell you I didn't notice any appreciable difference when I went to the "correct" Beru wire and ends.

But that wire from the coil to the distributor at 13K ohms, sounds a bit high...

Michael Salemi
1969 280SL
Signal Red w/Black Leather
Restored

merrill · « **Reply #23 on:** November 06, 2006, 20:36:58 »

Michael,
so, even if I had the aftermarket set, should the wire & connector resistance for the #1 cylinder still be higher than the rest?

the #1 connector is at a 90 degree angle while the others are straight. Another difference is the #1 connector is red and there is a scrw on the connector that the wire goes onto.

the rest seem to be molded ends and with the exception of the metal cover are black in color

Matt

Matt
66 230 sl - "white"
78 300 D - Blue
98 C230

ja17 · « **Reply #24 on:** November 06, 2006, 23:18:11 »

Hello Matt,

Yes I agree with Michael, that coil wire sounds way to high. Replace it or its ends. Make sure your new coil wire has metal wire and not carbon cores.

The right angle cable end on #1 cyl. is original on Mercedes carbureted sedan engines. All the fuel injected engines of the era and all W113 engines had six straight connectors.

Normally the wires should be close as far as resistance. It looks like your #1 wire is not a match to the rest of the set.

Hopefully this will solve the miss. If not it will be one more thing put right and one less potential problem on your list!

Joe Alexander
Blacklick, Ohio

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Author Topic: spark plug question (Read 36905 times)

Vince Canepa

Vince Canepa

al_lieffring