This blog, in addition to the usual maintenance details for classic mini cars, an attempt is made to explain the "whys" and "wherefores" of the various jobs.

Sunday, 11 October 2009

Adjusting the Plug Gaps

After the plugs have been cleaned and the points trued-up as just described, the gap should be adjusted by bending the side electrode only. One of the inexpensive combination gauges and setting tools sold by plug manufacturers is a worthwhile investment. If an improvised method is used (Fig. 35) make sure that no leverage is exerted against the central electrode; otherwise the internal insulator will probably be cracked, rendering the plug useless.
The recommended gap of 0-025 in. (25 thousandths of an inch) will give best results under all normal conditions. If the plugs are prone to oil-up, a smaller gap may be tried—say, 0-020 or 0-022 in.—but this must be regarded as a palliative rather than a cure. If the prospect of an engine overhaul is rather remote, the use of a spark intensifier, as described on page 91, will usually enable the normal gap to be restored without the risk of misfiring or difficult starting.