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SPORT COMPACT PISTONS SPORT COMPACT PISTONS

Piston Terminology Shelf Piston Terminology

With over 300 individual forgings to choose from, JE is able to achieve specific piston design requirements while reducing overall weight.
DOME HEIGHT VALVE RELIEF
PISTON DECK TOP LAND RADIUSED VALVE PRECISION CNC SMOOTH RADIUSED 2618 LOW-SILICON
MACHINED RING
DOME AND DISH
STD OIL DRAIN BACK TOP RING GROOVE RELIEFS GROOVES DESIGNS MATERIAL
SPLIT OIL DRAIN BACK 2ND LAND
2ND RING GROOVE
3RD LAND
SIDE RELIEF
(FOR FULL ROUND PISTONS) OIL RING GROOVE
FORCED PIN OILER
WRIST PIN HOLE/ (CENTERED OR SPLIT)
PIN DIAMETER SINGLE OR DOUBLE
LOCK GROOVE
PIN LOCK GROOVE SKIRT
(AVAILABLE FOR
WIRE LOCKS) BOTTOM BAND
SLIPPER AREA TANG
(COUNTER WEIGHT
CLEARANCE)

Valve location terminology Piston to wall clearance
EXH.
Center line out is measured VALVE 4032 Alloy pistons
to where a 90° valve relief STOP Bore Range Min. Clearance
cutter would meet the deck
to the piston center line. Sport Compact 2.500 to 3.625 .0022 to .0028
Sport Compact 3.626 to 3.999 .0025 to .0035
EXHAUST
CENTERLINE
OUT EXHAUST 4032 Additional clearance guide lines
VALVE RELIEF PIN Drag Race +.0010 - .0020
INTAKE INTAKE VALVE Turbo/Nitrous +.0005 - .0010
CENTERLINE RELIEF
OUT Road Race +.0005 - .0010
2618 Alloy pistons
Bore Range Min. Clearance
EXH.
VALVE Sport Compact 2.500 to 3.625 .0025 to .0035
STOP Valve pocket depth measured Sport Compact 3.626 to 3.999 .0030 to .0040 HONED PIN FULLY MACHINED SIDE MACHINED OIL DIAMOND SPECIFICALLY DESIGNED LEFT JE FORGINGS FEATURE
vertically from the piston deck BORES RELIEF WITH LOWER DRAIN BACK HOLES TURNED AND RIGHT FORGINGS ALLOW ENLARGED PIN BOSS AND
to the deepest part of the SUPPORT BAND FOR ENGINEERDED FOR SKIRTS PRECISE VALVE RELIEF RING BELT RADII TO ENSURE
valve relief radius 4032 Alloy pistons ADDITIONAL STRENGTH SPECIFIC OIL CONTROL LOCATIONS FURTHER REDUCING OPTIMUM STRENGTH IN
Drag Race +.0010 - .0020 WEIGHT WHILE MAINTAINING CRITICAL AREAS
Forced Induction/Nitrous +.0015 - .0025 SUPERIOR STRENGTH AND
VALVE ANGLE Turbo/Nitrous +.0015 - .0020 UNIFORM CROWN THICKNESS
COMPRESSION
HEIGHT/ Road Race +.0015 - .0025
DISTANCE

GAGE POINT
.500” STD What is an FSR forging?
(.275 WHEN SPECIFIED)
INTERNAL
BRACING
FSR (Forged Side Relief) forging designs feature a reduced
skirt width and shorter wrist pin when compared to
Compression height traditional “full round” style forgings. The narrow EXTERNAL
.020 skirt helps minimize piston contact with the cylinder BRACING
wall that can cause friction and power loss while
the shortened wrist pins reduces the overall
1.175 weight. Some FSR forgings feature internal
8.347 5.433
CRANK 3.437 and external bracing to provide a more rigid
1.7185 construction while minimizing overall weight.
With thousands of race miles logged in the most
demanding applications like NASCAR, NHRA Pro
COMPRESSION Stock and IRL, these pistons provide the ultimate
BLOCK DECK
BLOCK HEIGHT: 8.347 1/2 STROKE: 1.7185 ROD LENGTH: 5.433 CLEARANCE: 0.020 HEIGHT/DISTANCE: combination of low-friction, lightweight design with
1.175
increased stability and strength. (Tech note: In extreme
horsepower applications the use of oil squirters may be
required).

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