Hi all,

Just thought I would ask the question here.

Have been trawling the net for images on the various colours of spark plugs depending on correct or incorrect mix settings.

Well, to me my plugs look ok, what do you think?

OK, Rich, Lean ?

Car had just done a 40 mile run, good open road running with last mile urban.

Left hand plug is from No1 cylinder, Right hand is from No 4

Standard Twin carb Mk3 Spitfire.

Regards,

Rich

They look perfect to me. Light brown deposits, no corrosion and no soot where it shouldn't be.

The black colouring on the ground electrode is just where it should be - it changes around the middle of the arc. That's good as it shows the plug is operating at the correct heat.

The only thing I'd look to check is the ring of black soot on the top of the threads. Is it just one solid ring with no patches of thicker soot? I can't see from this view. If it is, then the mixture is absolutely spot on.

What model of plug are they, just out of curiosity?

Hi Richard,

Glad to hear that, I was still worrying that I was running to Rich.

The plugs are a set I got from Rimmers some time back made by DENSO I believe.

Havn't had any trouble with them at all.

Still got a set of NGK's as backup tho.

Yep, the dark ring on the end of the thread is consistant all the way around. No darker patches or lumps of black soot that I can see.

Rich.

Excellent.

I've got NGK BP5E's in at the moment, and I think they run a little too hot. The porcelain is bone white (unlike yours which is light brown) and the soot on the ground electrode is almost touching the ring. Unlikely to be timing causing the heat as there's no evidence of predetonation.

I used to have NGK BP6E's in, and tried the 5 as the 6's took quite a while to burn off the carbon, but then again that was back when I had an electronic ignition related misfire, so I didn't really give them a fair evaluation. Might try the BP6E again sometime soon.