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Champion Spark Plug Identification System
Example:
57 a Y-GAP
:
The suffix letter to the right of the heat range number
signifies gap style. Plugs having no suffix letter are regular Commonly used in overhead-valve racing engines
gap. where sufficient physical clearance exists between piston
or valves. Plug heat range characteristics are slightly dif
ferent from other plugs as incoming fuel charge cools in
HEAT RANGE AND GAP STYLE sulator tip at high speed ... long tip runs hotter at lower
speeds ... an effective plug in wedge type combustion cham
In racing, you not only have a selection of various heat
ranges in a given reach and diameter, but you have a choice bers .. .this design offers excellent fouling protection from
of three to four gap styles in most ranges. rich mixture conditions ... when converting to this design
In many high-performance engines, insufficient piston or from retracted or regular gap plugs, ignition timing may
valve clearance exists requiring the use of “R” gap plugs. In have to be retarded slightly... plug design is not recom
these engines, another condition requiring “R” gap plugs mended for maximum output engines, highly supercharged,
is the extreme temperature and pressure differentials. or high percentage nitro-burners.
Many engines not subject to the above conditions may
use‘“Y” or “J” gap styles. The projected insulator (“Y” type)
offers many advantages for better performance. It projects
the spark deeper into the combustion chamber, has wider
heat range, and has more fouling protection.
Before assigning yourself to using the retracted “R” gap
because the projected types will not fit, attempt to use a
regular or “J” gap, you will have better fouling protection
and superior flame front propagation.
Make sure the heat range of the “J” or “Y” gap is cold R-GAP
enough for the application.
A retracted gap plug... electrodes are shrouded
... used in racing engines where physical clearance is lim
ited between pistons or valves... or cylinder design em
ploys cartridge fire... plug is not practical in street use
... it is primarily intended for competition use in highly
modified ... supercharged ... or high percentage nitro-burn
ing engines ... fouling protection is less than “J”.. .“Y”...
or “P” gap style plugs. Gap settings may be “customized”
by use of Champion CT-408 tool.
J-GAP
G-GAP
A conventional automotive type gap slightly mod
ified ... side electrode extends midway to the center elec OR
trode ... gap design requires less firing voltage at high
RPM...also protects from ingested particles wedging be P-GAP
tween gap and shorting out plug. Plug design offers good
fouling protection and excellent performance in many racing
applications.
A fine-wire plug intended for racing applications
NO SUFFIX LETTER where engine conditions require increased latitude of heat
range ... plug has good resistance to fouling. These plugs
Spark plugs without a suffix letter are usually regular are excellent performers in 2-cycle applications as well as
gap style. The side electrode may extend fully across the 4-cycle ... they are not generally recommended for super
bottom of the center electrode or be cut back slightly from charged or high percentage nitro-burning engines ... these
the midway point. The heat range rating of the plug usually plugs will accept rich mixtures and are effective where
determines this cut-back. cylinder-to-cylinder cooling or mixture differences exist.
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