GM LS1 / LS6 5.7L Gen III 4.000" Stroker Rebuild Kit with Spool Conrods and CP Bullet Pistons
LS1 / LS6 forged stroker rebuild kit for a 3.905-inch (+.007) or 3.915-inch (+.017) finished bore, 4.000-inch stroke and 6.125-inch rods. Choose from 6 CP Bullet piston options, with Spool conrods, ACL bearings and two Cometic MLS head gaskets. Requires a suitable stroker crankshaft, which is not included.
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LS1 / LS6 forged rebuild kit for a 4.000-inch stroker combination
This GM LS1 / LS6 5.7L Gen III stroker rebuild kit combines CP Bullet forged pistons, Spool conrods, ACL Race Series bearings and Cometic MLS head gaskets. Its 6 piston choices are selected for a Gen III LS1 or LS6 build using a 3.905-inch or 3.915-inch finished bore, 4.000-inch stroke and 6.125-inch conrods.
A crankshaft is not included. This package requires a suitable 4.000-inch-stroke crankshaft. If you also need a crankshaft, see the complete Spool LS stroker rotating assembly.
Bore size: 3.905 inches is +.007 inch and 3.915 inches is +.017 inch over the nominal 3.898-inch LS1 / LS6 bore. Have your engine builder measure the block and approve the machining and clearancing requirements before ordering.
LS1 / LS6 5.7L Gen III fitment
This shared kit is for the 5.7-litre Gen III LS1 and LS6 engine family with the bore, stroke and rod combination listed above. It does not suit the newer 6.7-litre Gen 6 LS6 or the older 454 big-block LS6. The selected pistons use 15-degree LS head geometry. Verify any aftermarket head and camshaft combination, valve clearance, deck clearance and measured chamber volume before assembly.
What is included
- CP Bullet forged pistons with rings, pins and locks
- Spool H-beam conrods with 7/16-inch ARP2000 bolts, with conrod and bolt upgrades available
- Optional gudgeon pin upgrades
- ACL Race Series conrod bearings and main bearings in the selected sizes
- Two Cometic MLS head gaskets, 4.060-inch bore and .051-inch thickness
LS1 / LS6 stroker piston choices
| CP part number | Bore (in) | Stroke (in) | Rod (in) | Compression height (in) | Pin (in) | Rings (mm) | Head geometry / notes |
|---|---|---|---|---|---|---|---|
| BLS1002-007 | 3.905 | 4.000 | 6.125 | 1.110 | .927 x 2.250 | 1.5 x 1.5 x 3.0 | LS 15-degree; check complete head/valve combination |
| BLS1009-007 | 3.905 | 4.000 | 6.125 | 1.110 | .927 x 2.250 | 1.5 x 1.5 x 3.0 | LS 15-degree; check complete head/valve combination |
| BLS1002-017 | 3.915 | 4.000 | 6.125 | 1.110 | .927 x 2.250 | 1.5 x 1.5 x 3.0 | LS 15-degree; check complete head/valve combination |
| BLS1009-017 | 3.915 | 4.000 | 6.125 | 1.110 | .927 x 2.250 | 1.5 x 1.5 x 3.0 | LS 15-degree; check complete head/valve combination |
| BLS1143-007 | 3.905 | 4.000 | 6.125 | 1.110 | .927 x 2.250 | 1.5 x 1.5 x 3.0 | LS 15-degree; check complete head/valve combination |
| BLS1143-017 | 3.915 | 4.000 | 6.125 | 1.110 | .927 x 2.250 | 1.5 x 1.5 x 3.0 | LS 15-degree; check complete head/valve combination |
Actual compression depends on measured chamber volume, piston crown, deck clearance and head-gasket dimensions. Have your builder calculate the ratio for the complete build.
Choose the remaining components for your build
Select your preferred conrods, bolt and pin upgrades, and bearing sizes using the options above. These pistons require a 4.000-inch stroke, 6.125-inch rods and .927-inch pins. They are not the piston combination for the standard 3.622-inch LS1 / LS6 stroke.
Your builder must check block clearancing, crankshaft and reluctor compatibility, piston-to-valve clearance, deck clearance, bearings and balance. Follow the instructions supplied with the actual components for machining, ring gaps, fastener installation and gasket requirements.
Retaining the standard stroke? See the LS1 / LS6 3.622-inch standard-stroke rebuild kit. For a wider engine or piston selection, see the general LS 4.000-inch stroker rebuild kit.
Confirm the block and final bore with your engine builder before ordering. The finished bore, piston clearance, deck height, piston-to-valve clearance, crankshaft, reluctor and bearing arrangement must suit the complete build. Piston availability does not establish an approved overbore for every block. The selected head-gasket opening must be larger than the finished cylinder bore and must clear its chamfer and chamber outline.
| Product Name | GM LS1 / LS6 5.7L Gen III 4.000" Stroker Rebuild Kit with Spool Conrods and CP Bullet Pistons |
|---|---|
| Brands | Spool |
| Engine | LS |
| Make | Chevrolet, GM, Holden, LS Chev |
Delivery & Freight
We are an Australian-based company that ships items nationally and internationally, usually within 48 hours of receiving your order. High-value items shipped internationally are sent via DHL Express, while lower-value items are sent via Australia Post Express unless otherwise instructed.
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Which LS1 and LS6 engines does this kit cover?
This kit covers the 5.7-litre Gen III LS1 and LS6 family, using the selected 3.905-inch or 3.915-inch finished bore and specified stroke, 6.125-inch rods and .927-inch pins. It does not suit the newer 6.7-litre Gen 6 LS6 or the older 454 big-block LS6. Matching bore and stroke alone does not confirm compatibility with every aftermarket head, crankshaft or bearing arrangement.
Does this LS1 / LS6 stroker rebuild kit include a crankshaft?
No. It includes the selected CP Bullet pistons with rings, pins and locks, Spool conrods, ACL Race Series conrod and main bearings, and two Cometic MLS head gaskets. It requires a suitable 4.000-inch-stroke crankshaft. See the complete Spool LS stroker rotating assembly if you also need a crankshaft.
Can I use the standard LS1 / LS6 crankshaft with these pistons?
These selected pistons are specified for a 4.000-inch stroke and 6.125-inch rods. They are not the piston combination for a standard 3.622-inch-stroke crankshaft. Choose the LS1 / LS6 standard-stroke rebuild kit if you are retaining the standard stroke.
Are these standard-bore LS1 / LS6 pistons?
The listed options use 3.905-inch (+.007) or 3.915-inch (+.017) finished bores, compared with the nominal 3.898-inch LS1 / LS6 bore. Confirm the block and final bore with your engine builder before ordering. The 4.000-inch stroke specification is separate from bore size.
Which piston specifications can I choose?
The selector and technical table list 6 CP Bullet choices for a 4.000-inch stroke, 6.125-inch rods and .927-inch pins, in 3.905-inch or 3.915-inch bores. Choose the compression height and crown for the measured block, head chamber and intended use. Actual compression ratio must be calculated for your build.
Can I use a different rod length or stroke?
The piston options in this kit are specified for 6.125-inch rods and a 4.000-inch stroke. A different stroke or rod length changes the required piston compression height and clearances. Confirm a different combination with Spool Imports before ordering.
Which head gaskets are included?
The LS1 / LS6 selection includes two Cometic MLS head gaskets with a 4.060-inch bore and .051-inch thickness. Your builder must confirm their suitability for the finished bore, bore-edge chamfer, cylinder-head chambers and required piston-to-head clearance.
Are conrod, pin and bearing choices still available?
Yes. The kit retains the general LS stroker rebuild kit's conrod upgrades, pin upgrades, and ACL conrod and main bearing size selections. Choose bearing sizes from measured crankshaft journals and the required clearances. Upgrade prices are shown in the selectors.
Will the block need clearancing or the rotating assembly need balancing?
Both must be checked for the actual build. A stroker combination may require block clearancing, and the piston, rod, crankshaft and associated rotating components must be assessed together for balance. Your builder must also verify crankshaft and reluctor compatibility, piston-to-valve clearance and all operating clearances before assembly.
What piston clearances, ring gaps and bolt settings should I use?
Use the current instructions supplied with the actual pistons, rings, conrods, bolts and gaskets, matched to the engine's intended use. Do not use a single generic clearance, ring-gap or bolt-torque figure for every LS1 / LS6 build.
