Spark plugs

[Bob G ✝︎]

I ran accross an add from NKG advertising their new Iridium spark plugs. These spark plugs as NKG claims offer superior ignitablitly with out sacrificing durability. the tapered ground electrode increases flame kernel expansion, while the superior heat range design is ideally suited to the demands of high performance enviroments. Specially designed to meet the needs pf serious enthusiast.
Iridium 1X spark plugs offer outstanding acceleration , high fuel efficency and long life.
The standard plug we use BP7ES is in the Iridium line a BPR7E1X stock number 4055 availible at NAPA stores. NKG technical can be reached at 877-4736767

Has anyone tried these out?

Bob Geco

[mdsalemi]

Bob,

Platinum, Palladium, and Iridium are similar metals.  I think the iridium plugs you speak of may be just a marketing gimmick in relation to platinum plugs; i.e. they may not offer anything more then platinum plugs; the claims they make may be true but may be more related to the plug design then to the electrode metallurgy!

That being said, I've heard that platium plugs are a no-no for our cars as they foul too easily with our rich mixtures.

I'll put my NGK's back in for the drive to Blacklick!

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

[Benz Dr.]

They used platinum plugs in snowmobiles for years because the cheap 2 cylcle oil that everyoneused would foul out the plugs. Carbon won't stick to platinum.
The early PP's had a reallysmall electrode and I remember this guy complaining to me that his plugs were no good because the electrodes were all worn out. I pointed out that modern PP's have the electrode inside the insulator and his plugs were still OK. The main problem that most people have with PP's is that they're resistor type and this isn't something you need in low voltage inition systems.
Platinum was used in stationary gas engine ignitors over 100 years ago - it's not new at all. In the case of engines that ran on kerosine platinum was a must. They often used a crude system similar to water injection to keep the cumbustion chambers from loading up with carbon.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org

[Bob G ✝︎]

I took the advice of Dr Benz & michael Salami and returned the Iridium spark plugs for the stock BP7ES NKG choice. Whatis the gap suppose to be set at ?

Bob Geco

[Benz Dr.]

Did I say not to use platinum plugs? I can't remember.....

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org

[knirk]

Bob,
from previous posts it looks like 0.035" / 0.9mm is the most commonly used gap size. This is the same as listed in the Haynes manual for resistor type plugs. For non resistor plugs they list 0.028 - 0.032" / 0.7 - 0.9mm.

Per G. Birkeland
69 280 sl aut 834
Norway

[mdsalemi]

Followups:

Dan doesn't remember what he said.  What I got out of it was this:

1)  Platinum is OK, even preferable because carbon (fouling) won't stick to it.

2)  Problem is that most platinum plugs have "R" designations meaning resistor; if you are using non-resistor wires and non-resistor plug connectors, that's fine.  But most of us have the proper plug connectors which have the resistance.  You don't mix them.

Note that I use the NGK's for normal driving and put back the Bosch for show.  YOu are more likely to find the NGK's in the BP6 and BP7 at a motorcycle shop.  These plugs were designed for hot engines, high RPM, and lots of fouling which is what you find in motorcycles and probably why they work so well in our engines.

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

[70chevelle]

Can't you just remove the screw-on top of a resistor plug to make it a non-resistor plug?  (I know I did!)

[George Davis]

70chevelle and all,

Unscrewing the end won't change the resistance.  A bit o' trivia from the NGK web site:

Q: When should I use a resistor spark plug?

A: NGK "R" or resistor spark plugs use a 5k ohm ceramic resistor in the spark plug to suppress ignition noise generated during sparking.

NGK strongly recommends using resistor spark plugs in any vehicle that uses on-board computer systems to monitor or control engine performance. This is because resistor spark plugs reduce electromagnetic interference with on-board electronics.

They are also recommended on any vehicle that has other on-board electronic systems such as engine-management computers, two-way radios, GPS systems, depth finders or whenever recommended by the manufacturer.

In fact, using a non-resistor plug in certain applications can actually cause the engine to suffer undesirable side effects such as an erratic idle, high-rpm misfire, engine run-on, power drop off at certain rpm levels and abnormal combustion.







George Davis
'69 280 SL Euro manual

[Naj ✝︎]

Non-Resistor Platinum plugs that I currently use:

Bosch W8DP
NGK   BP7EVX

Both have removable caps.

naj

65 230SL
68 280SL

[Bob G ✝︎]

I better recap whats on my old 280SL before being skolled again. I replaced the spark plug wires with the factory OEM wire set from Germany. The distributor is a Bosch 009 distributor but no electronic ignition, the coil is from a 250SL according to Tom Hanson and the white tinna miggimmy is an early type  that sits besite the distributor. Dan Caron's rebuilt me a Bosch 051 distributorwith points cap and condensor new which is not in the car right now and I have a crane XR-700 kit ready to install when I have the distributor switched. I also gotthe correct coil wire the screws to the distributor and the positive side of the coil.
Hope I got the right spark plugs NKG BP7ES none resistor plugs.
Any recommdations about the coil?

Bob Geco

[Vince Canepa]

The ends that fit on the spark plugs (boots, whatever you want to call them) are a 5K ohm resistor.  Adding resistor plugs is redundant and my have a negative impact, especially for those still running the stock points/coil ignition.

I run NGK B7ES (non projected tip) and have for over 30 years.  I've tried Bosch platinum and didn't notice any negative/positive effect.  My plugs used to foul a bit after 6,000 miles or so when leaded gas was around, but don't anymore (the BP7ES projected tip plugs used to foul worse in my case which is why I stuck with the B7ES).  If I remember correctly, the manuals call for .024" gap (with the stock ignition).  I'm not sure the stock ignition can perform well at .035" gap.

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

[Cees Klumper]

Hey Vince - my caps/boots (the ends of the wires) are 1K ohm resistance. On some (AFAIK non-stock) wire sets, the boot to no. 1 spark plug is 5K ohm (the others being 1K ohm) and angled rather than straight.

quote:Originally posted by Vince Canepa

The ends that fit on the spark plugs (boots, whatever you want to call them) are a 5K ohm resistor.  Adding resistor plugs is redundant and my have a negative impact, especially for those still running the stock points/coil ignition.

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic

[mdsalemi]

quote:Originally posted by cees klumper

Hey Vince - my caps/boots (the ends of the wires) are 1K ohm resistance. On some (AFAIK non-stock) wire sets, the boot to no. 1 spark plug is 5K ohm (the others being 1K ohm) and angled rather than straight.

quote:Originally posted by Vince Canepa

The ends that fit on the spark plugs (boots, whatever you want to call them) are a 5K ohm resistor.  Adding resistor plugs is redundant and my have a negative impact, especially for those still running the stock points/coil ignition.

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic

Cees/Vince et al.

If you purchase an original wire set from MB, or a "duplicate" made with Beru wire and parts from any number of suppliers, you'll get the non-resistor wire and 1K, all-straight plug connectors.  This is generally accepted as a "correct" wire set.

If you buy certain aftermarket kits, including those Bosch branded you'll get somewhat of a "universal" MB kit that includes 5 straight 1K connectors, and one angled 5K connector for #1 plug.  I've had both and there isn't an appreciable difference in operation, but in concour judging of course there is.

Joe Alexander and National judge Pete Lesler both agree that the angled set is technically for a carbureted sedan (W111 and or W108??).

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

[Vince Canepa]

I am holding one of my "boots" in my hand as I write.  It is an original supplied with the car when new.  It is a BERU BA4/14/5.  It still has the gold cad plated metal "jacket" bottom section with a brown bakelite upper section.  After 38 years it still measures 4.6K ohms.  All my "boots" are original, straight connectors.  I have my original black PVC copper core wires, although I don't run with them any more.  The carbureted sedans (114/108) had a 90 degree "boot" for #1.  I had several of those sedans and can vouch for that.

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

[mdsalemi]

My original Beru's from my 1969 are 1K connectors, all straight.

My first, Bosch replacement set was 1K straight, 5K angled for #1.  That's what they list as "correct" in their book.  It works; it is cheap and readily available from any Bosch dealer.

My running and current set is all new Beru, all 1K, made for the car by Mercedesparts.com with current Beru parts and wire.

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

[Raymond]

The old set I took off and the new set I got from MB were both the angled #1. I didn't see any indication that it was different resistance.  Why would having an extra 4Kohm on one wire make sense?  Wouldn't the car run better without attenuated spark on #1?

Ray
'68 280SL 4-spd Coupe

[Vince Canepa]

I still have some boots from my 114 car.  They are 1K straight, all bakelite.  However, those are from a car with transistorized ignition and were used with the 1K 90 degree ends at the distributor (90 degree ends are required to clear the snap on black plastic cover).  Mt SL is straight coil/points ignition and at the distributor the there is only a straight rubber boot (no resistor).

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

[Benz Dr.]

The sets with the angled spark plug end for number one cylinder are only for carb type engines. You need that to fit behind the distributor.

If you gap your plugs at .025 or less the engine will likely miss. It doesn't matter if you have the early plug ends or the later metal ones they should be 1K ohms. Anything other than metal core is useless on these cars.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org

[Vince Canepa]

I have to admit I've been scratching my head over the 1K vs. 5K ends.  Going back to the Service Manuals, Job 82-20 in the early book calls for 5K spark plugs with 1K ends.  The same section of the later book calls for 5K ends and that is what my car was delivered with when new.  The overriding comment in the manuals is that the total resistance must be between 13K and 16K - above which high speed misfires may occur.

I stand corrected on the gap - I was trying to recall that from memory.  My Owners Manual calls for .8mm/.314" and that is what I have them set at.

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

[Vince Canepa]

Maybe I should just quit before I get more messed up.  I reread my Owners Manual (with my glasses on).  I quote "The electrode gap of these spark plugs is uniformly new 0.0196 in. (0.5mm) ----- If the electrode gaps are burned down to a gap of approx. 0.0314 in. (0.8 mm), reset or repalce spark plugs".  Now at least I have correctly quoted the Owners Manual.  The experts on these cars my choose to differ with the above quote, based on their experience or subsequent service information.

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

[Bob G ✝︎]

What is the difference between the bakelite spark plug ends and the all metal ends? I think my ignition wires are correct? Are the early bakelite spark plug boots still availble and what do you ask for?
Is it a concours point thing or a driving performance improvment?

Confused
Bob Geco

[Vince Canepa]

I'm not sure why they changed to the metal jackets.  Maybe for further radio suppression reasons.  I've noticed that all the modern German cars (that still have plugs wires as opposed to coil-on-plug setups) seem to use metal-jacketed ends.  Also, from what I can tell reading the Service Manuals, this seemed to be evolving through the years.

I would think that as long as the total resistance of the system is within spec (13K to 16K) both running and radio suppression needs are satisfied.  Modern radios may also be less interference prone, so perhaps going below the minimum is acceptable.  Afterall, the experts here are recommending the 1K ends and it would be hard to get to 13K using them.

For concours requirements, things are a bit murky to me.  I just know what my car was delivered with.  Most 230SLs I have seen came with the Bakelite ends and obviously, based on my car, they started using metal-jacketed ends sometime before my car was built.  It may also be that the metal-jacketed ends were only fitted to cars with the radio suppression package (like the copper spring thingy for the hood).


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

[ja17]

Hello,
The early 1,000 ohm resistors spark plug ends were #000 159 2189, the later metal shielded ones were 5,000 ohms #000 156 3210. I am not sure when they changed to the 5,000 ohm, possibly with the addition of the factory electronic ignition.
According one service manual, the resistor ends should be replaced when the entire wire assembly reaches 20,000 ohms or more.

Here is a photo of some original spark plug wire ends. Yes the right angle one is for a carbureted engine.

Download Attachment: spark plug wires.JPG
54.9 KB
Joe Alexander
Blacklick, Ohio

[Benz Dr.]

(sigh )
OK, one last time.
Bakelite ends for 230SL
Same ends with metal covers for 280SL

13,000K ohms is WAY too much resistance. The black coil is only 13,000 volts - that car probably wouldn't even start.
If you have resistor ends on the coil wire and distributor cap you have 4K right there. Add another 5K for the rotor ( no one EVER mentions the rotor do they ? ) and now you have only 6,000 volts to fire the plugs. Add a carbon wire for good measure and have fun.
I just use the plugs as they come gapped out of the box.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org