Don't use Platinum plugs on vintage MB?

[Tony H]

In the latest STAR mag there was an article where it said MB cautions not to use Platinum plugs on vintage MB's? Any one know why?

[Tomguy]

The spark system isn't strong enough to keep the much smaller spark area clean. If you have a modern spark system (or at least a higher capacity one) it isn't an issue.

[Frank Reiner]

Originally Posted by Tony H

In the latest STAR mag there was an article where it said MB cautions not to use Platinum plugs on vintage MB's? Any one know why?

1) A caution and/or recommendation made without an explanation or line of reasoning, is, at a minimum, to be viewed with skepticism, and usually should be disregarded.

2) The fine-wire electrodes of precious metal spark plugs require less voltage to establish a spark, and less energy to maintain the arc kernel.

The scribes may have confused electrode material with internal resistors.

.

[Idle]

Advice I received from a Mercedes Tech at a well known Dallas Mercedes dealer.........

Older plugs were made to run hotter, whatever that means. Due to the type of fuel used at the time the plugs would foul quickly so the plugs were built to run hot to burn off the fouling. You still had to change plugs about every eight to ten thousand miles as they were used up by then.

Newer plugs are for engines that use a different formulation of fuel from the 60's. Since the lead is gone the plugs don't foul out as quickly so they can run cooler. And they are made to do just that.

So putting a cooler plug in where a hotter plugs was originally is supposed to make the cooler plugs foul out quicker. At least that's what I was told. I don't know enough about the subject to make any decisions on this.

But in the case of the older Mercedes there is another reason to stick with the older number plugs. I installed newer plugs in my 230 and suddenly I was hearing the tick, tick, tick through my radio on AM. The Tech said to look at the metal shielded plug caps. On Mercedes the resistor is built into the metal cap and nowhere else. And by using plugs not designed for that car I was screwing up the entire ignition system. Or perhaps I should say the radio system.

This info is about 30 years old so any additional info would be welcomed.

[fonzi]

I believe I was told that you want to keep the overall resistance down on the older cars. Apparently adding resistors will keep newer more sensitive electronics systems and radio reception better. I honestly don't know if this is true. I've never had any issue with the old or new radios in any of my cars, but I do always try to get hot running non-resistor plugs (NGK bp5es) because I want to burn off the fouling I'm going to get with these older engines that run rich and even burn oil.

[Tony H]

Thanks for the responses. So if I were running a more modern ignition system (EDIS, COP, CNP etc) I could use more modern plugs of the correct heat range?

[rwd4evr]

That is what I understand to be true. Same as fonzi stated.

I'm thinking of an atempt at modifying a GM HEI distributer to use. Besides the occasional module failure they are bullet proof cheap and will shock the **** out of you! stock good to 6500+ and can be tuned for advance curve easily. vaccum and computer controlled advance available too. The big cap could be disguised as mb parts too.

[oldsinner111]

Plat. Plugs are ok,unless its a resistor,when you are to use a non.The real problem is the fine wire electrode.There are some plat. plugs with larger electrodes.Most older engines have dirt in the combustion area,and fine particles will short out the plugs fast.

[Frank Reiner]

Originally Posted by Tony H

Thanks for the responses. So if I were running a more modern ignition system (EDIS, COP, CNP etc) I could use more modern plugs of the correct heat range?

Once again, the choice of electrode material is not at issue. Precious metal (platinum, palladium, iridium) electrodes have been in spark plugs since the 1940s.
Newer systems do not deliver higher voltages; the required voltage to start the arc across the electrodes is a function of gap, mixture ionization, and cylinder pressure.
Newer systems can deliver greater energy [HEI=High Energy Ignition] to the arc once it is established, and often will exhibit greater arc duration.

[Graham]

It is well established we should not use those new-fangled plugs on our older Benzes. Use the ones that are recommended for your car. This is a link to a post made by one of the old time experts who unfortunately is no longer with us. http://www.peachparts.com/shopforum/27288-post6.html

Resistor plugs actually work fine, at least on the M117 Djet. I ran my 72 Djet for 20 years with them. But the general thinking is to use non-resistor plugs and that is what I am now doing (without any noticeable improvement )

[vandor]

Originally Posted by Frank Reiner

1)...

2) The fine-wire electrodes of precious metal spark plugs require less voltage to establish a spark, and less energy to maintain the arc kernel.

The scribes may have confused electrode material with internal resistors.

.

I work al ot with another brand of vintage cars and the general experience is that platinum plugs often cause poor running.
AFAIK their only advantage is that they last a very long time, not really an issue with classics, as they are not driven that much.

[Idle]

Originally Posted by vandor

I work al ot with another brand of vintage cars and the general experience is that platinum plugs often cause poor running.
AFAIK their only advantage is that they last a very long time, not really an issue with classics, as they are not driven that much.

I remember reading a Road and Track article from the early 70's where Manney was speaking of a new kind of plug Porsche was using while racing. They were platinums! The big advantage was they didn't need changing during the race, they would go the entire 24 hours without breaking down!

The big disadvantage was they cost $600 each.

[Mark DiSilvestro]

FWIW, for years I used Bosch platinums in my '72 w114 250. The only problem I had was when I switched to Bosch copper, based on people saying not to use platinums. Plus the coppers were cheaper. It was winter and the coppers started fouling. Switched back to platinums, with no further issues. Now my 250 had the transistor ignition, with supposedly a hotter coil. So maybe that helped.
However, I also used Bosch platinums in my '60 220S Fintail without problems for the few years I drove it.

Happy Motoring, Mark

[alabbasi]

I have no idea why, but they do make old MB's run like crap.

[HarvAMG]

Pierre Hedary has a great discussion on plugs for vintages Mercedes.

https://youtu.be/ocEMJ00XPLI?t=18m30s

Watch was he says about which plugs to buy. Very interesting.