What Should I Run For Spark Plug Gap And Spark Plug Brand?
S&S has used the following spark plugs in V2-Style Long Blocks with good results: Autolite 4265, Champion RN12YC, Harley-Davidson 5R6A, and NGK BPR 4ES. In general, same spark plugs work for Shovelheads if equipped with S & S Shovel-Style cylinder heads or 1975-1984 Harley-Davidson cylinder heads designed for long reach plug.
Install spark plugs with gap recommended by ignition manufacturer. Typically, .035-.045" is recommended for electronic ignitions, .022" for points.
What Should I set My Ignition Timing At?
S&S recommends using electronic ignition with adjustable advance curve in Super Stock® and Super Sidewinder Long Blocks. Adjustable curve permits slowing rate of advance to control or eliminate pinging under heavy load or when elevated temperatures or poor quality gasoline are encountered. Install ignition according to manufacturer's instructions. Leave spark plugs out while static timing to ease flywheel rotation.
Flywheels in S&S Big Twin-Style Long Blocks have three timing marks:
( F ) = Front cylinder firing mark, 35 degrees before TDC with vertical line in center of hole.
See caution below.
( R ) = Rear cylinder firing mark, 35° before TDC with dot in center of hole.
( T:F) = Front piston, Top Dead Center with colon (:) in center of hole.
Most fully electronic ignitions are timed at TDC. Points and other ignitions with mechanical advance are timed at front cylinder firing mark. With correct mark centered in timing inspection hole, ignition at full advance will occur 35° before TDC. S&S, however, recommends setting initial timing at 32° BTDC. This can be accomplished by setting the ignition to fire when flywheel mark is leaving timing inspection hole on left side.