Which spark plug gap is correct?

[WRe]

Hi,
I basically ask myself which value is the right one, that of the vehicle manufacturer (Merc 0.5mm) or that of the spark plug manufacturer, especially because e.g. NGK (0.8mm) not only specifies the gap for a special spark plug in its catalogues, but also specifically relates this to a specific vehicle (see NGK vintage cars -Catalogue: https://www.ngkntk.com/de/service/downloads/#Kataloge ).
I am therefore more inclined towards the information provided by the spark plug manufacturer.
As an aside, I've used Champion spark plugs (N7Y, cross reference to NGK BP7ES) for many years, which only started to show signs of fatigue (rough idle, poor start-up response) after almost 20,000km, whereas the highly acclaimed NGK plugs (BP7ES) failed after less than 3,000km, which is not what they're supposed to do looked at, but they no longer ensured idle running.
...WRe

[rwmastel]

Distance? Do you mean what we in US call "gap"?  There are no headings on the chart, but I assume you refer to the 0.8 measurement?  Do Champion and Mercedes have specification different than 0.8?

[Benz Dr.]

I use .032'' which is .8 mm   I only use nickel plated spark plugs such as Bosch or NGK. I avoid zinc or black oxide plugs that tend to seize in the spark plug hole and pull threads. Although not advised, I use a little bit of nickel anti-seize to prevent thread galling. We are using Autolite 64 right now which are non resistor. 

I only use non resistor plugs. Resistor plugs are often 5K ohms which you don't need. No carbon core wires and 1K ohm spark plug terminals. Ideally, you only want about 6K ohms in the entire ignition system. The rotor is 5K which most people never consider. 

[mdsalemi]

I’m using the Pertronix ignition system with their high voltage “Flamethrower II” coil. They recommend opening up the spark plug gap to .035”. I’m running NGK BP6ES non-resistor plugs.

All seems to run well. This setup has been in since 2011.

Though a threaded steel spark plug into an aluminum head is unlikely to experience thread galling, I too add a little anti-seize on the spark plug…always makes it easier to get in and out.

 

[wwheeler]

Regarding anti-seize, nickel based is generally preferred over copper and what Dan mentioned. Has better corrosion resistance than copper. Not a huge difference, but why not use the better to start with. I used nickel anti-seize on the plug threads, but use VERY little. Much lees than on a typical threaded fastener.   

[69280sl]

Slightly off topic but...

I just replaced my plugs with NGK BP5ES11. The "terminal" does not screw off. So it seems Im adding another 1K ohm resistance, and,
the connection with my OE type BERU wires is not as well bonded (electrically).
Will either of  these conditions have a noticeable effect?

[awolff280sl]

NGK BP5ES-7832 is the part # for plug with removable "terminal"

[69280sl]

Thanks Andy
7732 is what I have.

[mdsalemi]

Gus,

About a year and a half ago, someone noted that NGK was discontinuing both the non-resistor plugs, as well as the "removable" terminals on top. That caused, around here at least, a bit of a "run" of the market as people ran out and wiped out the remaining inventory of these at the local auto parts stores.

[Benz Dr.]

I'm using Autolite 64 plugs now.  Non resistor and the same range as W9DC or BP5ES.

[69280sl]

Dan
An Autolite write-up describes this as a resistor plug. 

[Benz Dr.]

Not supposed to be. I'll check that out with an ohm meter.

[rwmastel]

Resistor Value 4k Ohm

Listed under product specifications:  https://www.autolitesparkplugs.com/autolite-64-nickel-spark-plug