Diamond Forged Pistons - GM LS1-based custom-bore - 4.000 in Stroke, 6.125 in Rod
Diamond Forged Pistons - GM LS1-based custom-bore - 4.000 in Stroke, 6.125 in Rod
Diamond forged pistons for GM LS1-based custom-bore
Eight-piston engine-build kits for the specified crankshaft, connecting rods and finished cylinder bore. Select the bore, crown and nominal compression ratio, then choose the standard or upgraded H13 gudgeon-pin kit.
Representative Diamond catalogue photograph. Crown shape, valve reliefs, skirt finish and supplied components may differ by the selected part number.
Made to order and delivery
Special-order, made-to-order pistons. Allow approximately 5–6 weeks for delivery, pending Australian customs processing time. Manufacturing schedules, international freight and clearance can extend this estimate.
Features and included components
- Forged 2618 aluminium construction, machined in the USA.
- Machined crown and valve-relief profiles; verify the chosen cylinder head and camshaft combination.
- Offset pins and moly-coated skirts.
- Trend gudgeon pins, the listed ring set and pin retainers included.
- Standard-pin and upgraded H13 kits available as separately priced options.
- Catalogue compression figures use a 0.040-inch head gasket; actual ratio depends on the measured engine assembly.
Build dimensions
- Crankshaft stroke: 4.000 inch
- Connecting-rod length: 6.125 inch
- Compression height: 1.115 inch
- Gudgeon-pin diameter: 0.927 inch
- Quantity: eight pistons; rings, pins and retainers included. Oil-rail supports are included where indicated in the kit table.
Kit selection
| Kit SKU | Bore | Crown volume | Nominal ratio | Included pin | Ring set | Ring thickness | Retainer | Oil-rail supports |
|---|---|---|---|---|---|---|---|---|
| 11518-R1-8 | 4.000 IN | -2.00 CC | 11.10:1 | G9272500185 | 09454005 | 1.20 MM x 1.20 MM x 3.00 MM | 015104-32 | Yes |
| 11520-R1-8 | 4.000 IN | -15.00 CC | 9.70:1 | G9272500185 | 09454005 | 1.20 MM x 1.20 MM x 3.00 MM | 015104-32 | Yes |
| 11521-R1-8 | 4.030 IN | -15.00 CC | 9.80:1 | G9272500185 | 09454030 | 1.20 MM x 1.20 MM x 3.00 MM | 015104-32 | Yes |
| 11522-R1-8 | 4.125 IN | -7.00 CC | 11.10:1 | G9272500185 | 09454065 | 1.20 MM x 1.20 MM x 3.00 MM | 015104-32 | Yes |
| 11518-R1-8-H | 4.000 IN | -2.00 CC | 11.10:1 | H9272500225 | 09454005 | 1.20 MM x 1.20 MM x 3.00 MM | 015104-32 | Yes |
| 11520-R1-8-H | 4.000 IN | -15.00 CC | 9.70:1 | H9272500225 | 09454005 | 1.20 MM x 1.20 MM x 3.00 MM | 015104-32 | Yes |
| 11521-R1-8-H | 4.030 IN | -15.00 CC | 9.80:1 | H9272500225 | 09454030 | 1.20 MM x 1.20 MM x 3.00 MM | 015104-32 | Yes |
| 11522-R1-8-H | 4.125 IN | -7.00 CC | 11.10:1 | H9272500225 | 09454065 | 1.20 MM x 1.20 MM x 3.00 MM | 015104-32 | Yes |
Fitment and installation
For LS1-based engine builds with suitable sleeves or an aftermarket block. The listed 4.000-inch and larger bores must not be treated as a routine overbore of a production 5.7-litre LS1 block. Confirm the block and cylinder-head combination before ordering.
Requires a 4.000-inch stroker crankshaft and the listed 6.125-inch rods. This is not a standard-stroke replacement piston.
The gudgeon-pin diameter for this group is 0.927 inch. Rod small-end diameter, rod length and pin retention must match the selected kit. The standard and H13 options are priced as complete eight-piston kits.
Have your engine builder check piston-to-bore clearance, ring gaps, deck height, piston-to-valve clearance and rotating-assembly balance before assembly. Nominal compression ratios are selection guides, not a substitute for measuring the chamber, gasket and deck volumes.
BBT workshop support and related parts
Boost & Tune can help coordinate the piston, rod and crank dimensions with your planned naturally aspirated or boosted LS build. Contact BBT with your engine code, measured bore, cylinder heads and target use before ordering if the combination is not already specified.