Lodge HF (or other muti-electrode plugs)

[Simon.Gardiner]

The main Leader project arrived with some very fetching pink spark plugs showing in the heads of the engine/gearbox lump. I assumed these were very old relics from a long-past life but they're turned out to be essentially unused (I found the original packaging with some of the bits) and to me extremely strange multi-point things.
I can't find heat ranges for these and apparently you're not supposed to touch the gaps. Are these really 'one plug fits all' and has anyone used these (or any other multi-point plug) - are they any good?

.
SG

[dave.owen]

I use one simolar in my 27 model c

[Roger Gwynn]

I used them in my 1980 Guzzi with success, would use them again.

[nevhunter]

When they tested Multi Points with single ones there was no advantage. Its unlikely it would fire more than ONE at any time. Electricity takes the path of least resistance. Nev

[Roger Gwynn]

I believe that the idea was if one gap was fouled another would take over, a bit redundant these days.

[Simon.Gardiner]

But they never need gapping and have an enormous heat range?!
That's part of the puzzle for me.

SG

[nevhunter]

Lodge were a well respected Brand of plug. Nev

[Roger Gwynn]

They were listed by Ariel as the preferred plug for most if not all years.

[cmfalco]

I believe that the idea was if one gap was fouled another would take over

I suppose it could happen, but I've never seen a plug where fouling bridged the gap between the electrodes. However, even if it did, it would provide a short, making the other three electrodes useless. Instead, my experience with fouling is a conductive coating forms on the insulator that provides a short. But, if that happens, it wouldn't matter how many electrodes there were, the spark always would follow the lower resistance short along the insulator.

Aside from disadvantages of the geometry, the only advantage would be that the spark would always jump to the nearest electrode, so as one wore away another would "automatically" take its place, meaning the plug would last four times longer before the gaps of all of them were too large for the spark to jump.

But they never need gapping and have an enormous heat range?!

That plug cannot have a heat range any larger than any other plug, for the reasons given below. However, "heat range" is an ambiguous term with spark plugs. Because the thermal properties of Al and cast iron are different, as well as the design of heads, a range of insulator lengths on a given series of spark plugs is required for one of them to have the "right" length needed to extract the heat from a given engine.

Using NGK as an example, a hypothetical NGK B2ES would have a very long insulator, along which heat from the combustion chamber would travel slowly, so the end of it would remain hot. In contrast, an NGK B12ES would have a very short insulator, so it would be very efficient at extracting heat, and the end would remain cold. So, the "heat range" of NGK spark plugs runs from 2 to 12, due primarily to the lengths of the insulators. In any case, here, the term "heat range" covers the entire range of insulator lengths for a given series of plugs.

A given spark plug (e.g. B7ES) can only cope with relatively small variations in combustion chamber temperature before the tip becomes either too hot (resulting in preignition) or too cold (resulting in carbon build-up on the insulator). In other words, for a given series of plugs (e.g. B6ES, B7ES, B8ES) the range-of-heats that any one of these can deal with is limited by the length of its insulator. Although the series has a wide "Heat Range," any given plug has a narrow "heat range."

Many British engines with Al heads use either a B6ES or B7ES spark plug in order for the tip to be at the proper temperature for a given engine. Here, the term "heat range" refers to the specific insulator length of a given plug that keeps the tip of the spark plug at the Goldilocks temperature. Someone might say "B7ES has the right heat range for my engine." But, again, there's nothing about the insulator of that multi-gap plug that would give it a "heat range" any wider than any other plug.

[nevhunter]

Insulators (The Part in the combustion chamber) can foul because some of the antiscuffing oil additives are Likely to remain on the surface of the Insulator and burn onto it and short it out. A scraper made from an early style metal Hairpin with the straight bit sharpened to a chisel Point is effective there. Nev