We did it again at Hallett this past weekend, that's a 2nd and two 1sts in the last 3 outings. Wunnerful.

However, comma.... Please take a look at the attached photo and tell me if you know what might cause the deposits. You're looking at the #4 plug, which is the worst of the 4. In fact #1 has little or no discoloration, and it gets worse as you progress aft (2 is worse than 1, 3 is worse than 2, etc). The plugs were fine when they were installed (at the track Sunday morning); they were slightly used, but did NOT have rust colored deposits on them. As you can see in the pic, the deposits are also on the interior of the plug, not on the electrode or the insulator, just the interior wall of the metal barrel. I am thinking this may be due to water in the combustion chambers, but I'm open to suggestions. (I may have lost a little water from the cooling system... but we're talking damned little... during the day's activities.)

What about water in the fuel? I'm going to pump the last couple of gallons of fuel out of the cell and see if I find any H2O. Water in the fuel might make sense with respect to the #4 plug being the worst of the bunch... the fuel rail that supplies the injectors feeds from the rear, so #4 would get any water droplets before the other three injectors.

Other info... the engine was running fine all day, 5 separate sessions totalling about 85 racing miles. Post race compression check and leakdown tests have been performed and numbers are healthy (and virtually unchanged from pre-race). Fuel is a 50-50 mix of 91 octane pump gas and 110 octane leaded racing gas... basically the same mix I've used all season.

Any ideas are welcome.

Gary L.

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1971 142E ITB racer, 1973 1800ES, 2002 S60 T5