Jims Catalogue

FORGED PISTON SETS

TWIN CAM ® PISTONS

REPLACEMENT FORGED ALUMINUM PISTON

No.1608

JIMS ® pistons represent an advancement in piston design and function. These pistons now incorporate the latest oil control technology with 3mm oiling control ring grooves, and advanced piston skirt design. By reducing the oil control ring to a 3mm thickness there is less internal friction, which reduces heat, and creates more power. The piston skirts have also been optimized to take full advantage of piston support without incurring more friction. The rear pis- ton’s, non thrust face portion, receives a radial notch to clear the full skirt of the front piston. This design gives the front piston more support while still allow- ing proper piston-to-piston clearance. Replacement pistons retain original design piston notching.

RACE ONLY

JIMS ® Twin Cam ® piston sets are CNC machined from aerospace quality, forged 2618 aluminum alloy. Each kit includes directional pistons, precision ground wrist pins, rings, and clips. For more details see No.1606-IS instructions. BIG BORE TWIN CAM ® 100” SERIES II Use on 1999-present. Requires 4” bore cylinders and boring of case. PART NO. BORE STROKE PIN O.D. RINGS C/R No. 1603 4” std 4” .927” No.1491 9.56:1* TWIN CAM ® BIG BORE FLAT TOP PISTONS STROKER TWIN CAM ® DISHED 113” SERIES II Requires JIMS ® 4.5” Twin Cam ® Stroker Kit Assemblies PART NO. BORE STROKE PIN O.D. RINGS C/R No. 1607 4” std 4.5/4.625 .927” No.1491 10.19:1** No. 1607B 4”+ .010 4.5/4.625 .927” No.1493 10.19:1** STROKER TWIN CAM ® 113” & 116” SERIES I Requires JIMS ® 4.5” or 4.625” Twin Cam ® Stroker Kit Assemblies PART NO. BORE STROKE PIN O.D. RINGS C/R No. 1620 4”+ .005 4.5/4.625 .827” No.1428 10.19:1* TWIN CAM ® DISHED STROKER PISTONS *Compression ratios are approximate. STROKER TWIN CAM ® DISHED 116” SERIES II Requires JIMS ® 4.625” Twin Cam ® Stroker Kit Assemblies PART NO. BORE STROKE PIN O.D. RINGS C/R No. 1608 4” std 4.5/4.625 .927” No.1491 10.19:1** No. 1608A 4”+ .005 4.5/4.625 .927” No.1492 10.19:1** No. 1608B 4”+ .010 4.5/4.625 .927” No.1493 10.19:1** TWIN CAM ® WRIST PIN CLIP SETS No. 1602K - Replacement wrist pin clips for .827” wrist pins. Use on JIMS ® Series I 100” piston set No.1620. No. 1604K - Replacement wrist pin clips for .927” wrist pins. Use on piston set No’s. 1603, 1607, 1607B, 1608, 1608A and 1608B. *Compression ratios are approximate. *Compression ratios are approximate.

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Valve Pockets

Direction

Compression Height

O.D.

The compression height (C.H.) is measured from the cen- terline of the wrist pin to the piston deck (the top outer most edge of the piston w/out dome). A minimum piston- to-head clearance of .040” should be maintained when using steel connection rods. To determine this clearance, combine the compression height with a compressed cylinder base gasket’s thickness. COMPRESSION HEIGHT CLEARANCE Though dependent on several factors, JIMS ® recommends that valve pocket clearance be kept to a .060” clearance for both intake and exhaust valves. Note: Always check valve clearance with clay and fully solid tappets before turning engine over. VALVE POCKET DEPTH Unless otherwise specified, all compression ratios are based on stock heads, cylinder, and stroke. Refer to your equipment manufacturer’s literature for specifications. COMPRESSION RATIOS

**Compression ratios based on 85.9cc head with .040” head gas ket and 9.5cc piston dish at zero deck height.

* Compression ratios are approximate.

TWIN CAM ® PISTON SPECS.

TWIN CAM ® PISTON SPECS.

COMPRESSION HEIGHT

COMPRESSION HEIGHT

COMPLETE WEIGHT

COMPLETE WEIGHT

1603 1.270” 1620 1.125” 1607 1.188” 1607B 1.188” 1608 1.125” 1608A 1.125” 1608B 1.125”

1148g 1058g 1140g 1142g 1115g 1116g 1118g

1611 1.199” 1613 1.199” 1614 1.27” 1615 1.175”

1145g 1149g 1171g

1149g 1616 1.0825” 1148g 1617 1.125” 1143g 1618 1.125” 1145g

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