HKS Forged Pistons and Connecting Rods for Nissan GT-R
HKS have released their awaited forged pistons and conrod package for the VR38 engine recently as a compliment to their GT800 turbine upgrades. Designed to offer high durability, the HKS pistons are also designed to cope with much more power than standard.
Before getting too steeped in the technical specs, let’s run over the highlights of the HKS forged piston product. These pistons offer the same bore x stroke of the OEM pistons meaning the same displacement volume and that they’re a direct fit. What does change is the crown volume (concave) which increases from 4.49cc per cylinder to 8.01cc. This has the effect of decreasing the compression ratio from the standard 9.0 down to 8.7. Thanks to the forged hollow channel construction, the HKS pistons also weigh in at 25 grams less than the OEM items (420g vs 445g).
For full specs for the pistons and the conrods see the data below from HKS. For pricing, contact your HKS distributor for local pricing but expect to pay around 367,500 yen if you’re in Japan for the full set.
| Â | HKS Product | OEM | |
| Bore x Stroke | 95.5 X 88.4mm | 95.5 X 88.4mm | |
| Compression Ratio | 8.7 | 9.0 | |
| Â | Gasket Thickness | HKS t 0.8 | t 0.80 |
| Total Displacement (cc) | 3799 | 3799 | |
| Piston | Bore | 95.5 | same |
| Compression Height | 34.30 mm | same | |
| Concave Crown Volume | 8.01 cc | 4.49 cc | |
| Material | Forged (hollow channel) | Cast (hollow channel) | |
| Reference Weight | 420 g | 445 g | |
| Pin | Dimensions | 23 X 60mm | 23 X 62.5mm |
| Rings | Dimensions TOP B | 1.2 mm | same |
| Dimensions SEC B | 1.2 mm | same | |
| Dimenstions OIL B | 2.0 mm (3 pieces) | same | |
| Conrod | Small End Dimensions | 23mm | same |
| Big End Dimensions | 59mm | same | |
| Length | 165.1mm | same | |
| Material | SCM treated | Cast Steel | |
| Reference Weight | ~722 g | ~724.6 g | |
| Weight Variation | less than 1.0 g | – | |
| Bolt | M9 X P1.0 / 14.9T | same | |
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