ProForm 66277 High-Torque Starter for GM LS1, LS2, LS6 & LS7
$238.99
A brand-new ProForm high-torque, gear-reduction starter for GM LS1, LS2, LS6 and LS7 engines, with a billet aluminum mounting plate.
- Fits: GM LS1, LS2, LS6 & LS7 with a 168-tooth flywheel
- High compression: ProForm rates it for 15:1 engines, 3.75:1 sealed gear reduction
- Oil pan clearance: Offset design; housing can be rotated for chassis clearance
- Billet mount: Billet aluminum mounting plate
- All new: New components, not remanufactured
Amazon price as of Oct 9, 2026, subject to change. Check Amazon for the current price. Checkout is completed on Amazon, not through Planet X Performance.
The ProForm 66277 is a high-torque, gear-reduction starter for GM LS engines, built new rather than rebuilt. ProForm rates it for 15:1 compression engines and says it delivers 40 to 50% more cranking power than a stock starter, through a sealed 3.75:1 gear-reduction drive with full ball bearing construction. The offset design adds oil pan clearance, and the housing can be rotated on its billet aluminum mounting plate for more chassis clearance.
Key specs
| Brand / part number | ProForm 66277 |
|---|---|
| Compression rating | Up to 15:1 (per ProForm) |
| Gear reduction | 3.75:1, sealed (per ProForm) |
| Output | 1.4 kW (confirm with the manufacturer or JEGS tech support) |
| Voltage | 12 V |
| Construction | 100% new components, full ball bearing |
| Mounting | Billet aluminum mounting plate; offset design; housing can be rotated |
| Flywheel / flexplate | 168-tooth only (per ProForm) |
| Weight | 12.9 lbs (confirm with the manufacturer or JEGS tech support) |
| Warranty | Manufacturer warranty (confirm with the manufacturer or JEGS tech support) |
Fits
- GM LS engines: LS1, LS2, LS6 & LS7
- Required: 168-tooth flywheel or flexplate
- Not compatible: Pontiac GTO engine configuration (per ProForm)
In the box: Starter motor, (2) mounting bolts, a solderless terminal, a round-nose shim, and a housing shim (per ProForm’s instructions).
Check before you buy
- Tooth count: Confirm your flywheel or flexplate has 168 teeth
- Vehicle: ProForm says it doesn’t fit the Pontiac GTO engine configuration
- Clearance: If headers or a large oil pan are tight, the housing can be rotated on the mounting plate
- Setup: Check pinion clearance and backlash before first start, per ProForm’s instructions
Mounting hardware included.
Recommended: For replacement mounting bolts, we suggest the ICT Billet LS starter bolt kit (551681) or the ARP stainless LS starter bolt kit (430-3511).
Broken starter ear? If the outboard starter mounting ear on your LS block is cracked or broken, the Trinity Starter Bracket can repair it without machining. The block’s inboard starter bolt hole must still be intact. The Trinity can’t fix a block where the whole starter ear is missing.
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