Tech Tip - Spark Plugs

By: Allen Bishop

One of my great pleasures is to read the oft-told tales of pre- and early post-war racing. All sorts of mishaps plagued the drivers and teams of those times, just as is the case today. One frequent source of torment is rarely mentioned today however: spark plug maladies. Even the great Nuvolari couldn?t always avoid "oiling a plug" which "forced him to pit for a change." Today?s spark plugs are the classic quantum leap ahead from even those of 30 years ago.

One of the factors governing how your Ferrari performs, be it a 166 or an F355, is the spark plugs. What follows are some observations I have made over the years working on variations of the Ferraris in my shop.

To begin with, let?s discuss the current cars. Today?s Ferrari with its micro-managed fuel and ignition systems requires little in the way of spark plug maintenance. If plug performance is off, something other than the plugs themselves is the probable cause. In the interest of fuel efficiency and emissions, operating conditions within current Ferrari engines are very critical. Therefore, the plugs should be changed at recommended intervals - always - even if the plugs appear to be OK.

Like oil filters, spark plugs are sacrificial; they gradually deteriorate in service and finally this normal drop-off in performance turns to actual "decay" when a certain point has been reached. The Factory?s engineers, in conjunction with the plug manufacturer (currently Champion) have carefully worked out the proper interval for replacement as well as the correct type of plug for your car. The owner should adhere to the Factory?s recommendations for both make and heat range when changing plugs. Changing brands can lead to a change in the operating characteristics of the engine. The world is rife with spark plug "conversion" charts between brands, but the reality is that two different makes of plug that are supposedly the same may well interchange mechanically, but have slightly differing operating characteristics. On earlier cars this can lead to happy results, but is a pointless exercise in very late cars, and could lead to operating problems, or worse, physical damage. In some cases, such as the 288 GTO and F40, very special and costly plugs are specified. Play it safe, don?t deviate!

Earlier Ferraris can be made to run well on several makes of spark plug simply because the running conditions within the engine are not nearly as critical, assuming good tune and mechanical condition. My personal choice for years has been the NGK from Japan. The reason is simple. NGK pioneered the use of copper for the center electrode in their plugs. The use of copper for this element is a natural choice for two reasons. First, copper is an excellent electrical conductor and second, this material reaches operating temperature very quickly while also able, to a degree, to shed excess heat. In recent years, Champion has also adopted copper center electrodes, along with the marketing of a line of very high performance plugs which several Ferrari mechanics use regularly. An example would be the N6YC ("C" being for copper).

In the last few years, I have used the "V-Type" NGK plugs in the V-12s exclusively. Aside from being suitably expensive for the application, these little guys really fit the bill. They use a metal called "Palladium" for their central electrode. Palladium has all the positive assets of copper, with even greater resistance to heat and the adverse effects of high voltage. The end point of the center electrode in the V-plugs is very small in diameter; for this reason they are often called "fine wire" plugs. This tiny firing tip operates at a high, but controlled, temperature, making these plugs very resistant to

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