There is a well-known adage that says, “If it ain’t broke, don’t fix it.” It is something that should be heeded by us car guys and gals. Among Alfa Romeo owners, there is a corollary adage which applies to Weber carburetors: “If the car runs well, don’t mess with the carbs.” Webers are unlike most other carburetors such as those found on American vehicles. After an initial set-up as found in a service manual, the choice of needle and jet sizes for Webers is made on a basis of trial and error. I believe that it was Pat Braden, the late, great Alfa guru, who advised against trying to “tune” your Weber carburetors without checking other engine basics first.

I bring this up because for the thirteen years I’ve had my GT 1300 Junior, during which I’ve driven it over 14,000 miles, the engine has always run strongly. One issue, though, has been that the spark plugs quickly turn black, apparently from an overly rich fuel mixture. (The engine uses almost no oil; at most, a half-quart in between oil changes.) Rather than try to “adjust” my dual Weber carburetors, I replace the plugs. Spark plugs are less than five dollars each, and the set of four takes about twenty minutes to replace. As a rule, I have been swapping out spark plugs once a year at the start of the driving season.

Last year, when I changed the plugs (which have exclusively been NGK B7ES), I moved up to the next hottest heat range plug, the B6ES. In 2024 I put about 1,100 miles on the Alfa, and there was no perceptible performance difference with the hotter plug. However, when I pulled the plugs a few weeks ago to check them, I was impressed. To my eye, there was less build-up on the plug tips, to the point where I decided to leave the plugs in place. The one-step-hotter plugs did a better job of burning off deposits, without affecting drivability.

This was not easy to capture in photographs, but take a look at the two pictures and see if you can tell that the B6ES plug looks cleaner than the B7ES plug. I have two spare sets of the B6ES plugs, so if need be, I can quickly replace the set. But for now, I will leave them in the car and see how it goes. I’m expecting to possibly get a complete second driving season from them.

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