3/21/2021 0 Comments Spark Plugs
For example, on this Gen IV LS7 chamber, the plug is already biased toward the exhaust by design.See all 5 photos Spark plug indexing sometimes is necessary to avoid side-electrode contact with high-dome pistons.
Moroso offers different thickness spark plug washer kits to do this. Some theorists claim positioning the electrode in relation to the intake or exhaust valve may also be worth some powerat least on old-school chambers. To keep track of the electrode position, mark the plugs rear shell in line with the side electrodes open end. Indexing spark plugs refers to the orientation of the spark plug electrodes open end within the cylinder head combustion chamber. Whether the side electrode requires special orientation or indexing within the chamber is controversial. ![]() Modern angle plug heads and (for racing) extremely small volume combustion chambers have minimized the need for this. See all 5 photos This is the correct plug orientation according to most race engine builders. The side electrode gap faces up away from the piston dome, thereby achieving maximum clearance. If you run high-compression pistons and the gaps close up instead of widening as the plugs wear, definitely index the plugs this way. Some theorists once believed pointing the open end of the side electrode toward the chambers squish area or toward the exhaust side could be worth power. Again, with modern quick-burn chambers, the current thinking is theres usually no discernible power difference, but the final arbiter is, of course, actual dyno testing of the individual combination. See all 5 photos Some ignition theorists claim that, for max power, the side electrodes open end should point down toward the squish area away from the path of maximum entrance turbulence. They claim squish air is thrown right into the open, unhindered spark. Some even ricochets back off the side electrode and bounces into the spark again. Available from Moroso and other aftermarket sources, spacer washers of varying thickness can control the plugs electrode orientation. Moroso PN 71910 is a flat washer assortment for gasket seat 14mm spark plugs. For 14mm tapered seat spark plugs, use Moroso conical washer assortment PN 71900. Caution: Adding washers recesses the plug backward within the hole. Recessing a spark plug too far into the hole could shroud the spark, calling for more ignition lead than normal. See all 5 photos Old-school thinking: The open end should face the hotter exhaust valve, making it easier to start the fire. This orientation also protects the plug from fuel wetting caused by a rich airfuel charge. This is unnecessary with modern chambers, ignition, and fuel management.
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