M103: Bosch H8DC0 Gap?

[neilrr]

I just bought 6 new spark plugs off an ebay vendor. The plugs are new & unused but the boxes are a bit bashed & they look like they might be NOS.

I thought it prudent to check the gap & not knowing what it is meant to be looked on the internet.

There seems to be two schools of thought:

1) go with the MB spec of 0.8mm, or,

2) increase the gap to 1.0mm, which allegedly results in better burn & a smoother idle.

The car has recently had new MB leads, dizzy cap & rotor.

Anyone done this?

 

[Will]

I'd stick with the recommended 0.8mm. I think it's on the slam panel?

If you're not having any running issues, I wouldn't mess about with the standard spec.

IIRC - the school of thought with plug gaps was bigger gap = a fatter spark, but a smaller gap = a more reliable spark (doesn't have such a big gap for the spark to jump).

Will

 

[neilrr]

spark plug gap - PeachParts Mercedes ShopForum

m103 spark plug gap... - PeachParts Mercedes ShopForum

 

[Benzsc1]

I would stick with the 0.8 mm gap I have been having a nightmare trying to get my C124 running due to a weak spark (I even messed around with the gap and found that even with the fault I actually got the strongest most consistent spark out of two or three other gap sizes I tried.

 

[Will]

Personally, if the car has been running fine for ~ 20 years with O.E plugs gapped to 0.8mm then I'd be inclined to stick with it.

If you order plugs from MB now, are they still gapped to 0.8mm? (the last ones I bought a few years ago were)

Are you having any specific ignition related problems that are attributable to incorrect gapping of plugs (?)

Will

 

[neilrr]

No, no particular problems. I just read the posts from the people advocating a wider gap & what they said made sense.

 

[jaymanek]

i widen mine to 1mm, supposed to give a smoother tickover.

 

[neilrr]

0.9 was the gap I decided upon. They've been in a week or so & TBH I don't notice any difference.

 

[kth286]

of course with a single electrode plug, the gap gets wider as the miles go by anyway, from the erosion that occurs.

bearing that in mind your end result 5k/10k down the road, the gap will be more than you anticipated.

I would set the gap to spec.