Allstar Performance spark plug index shims are stackable washers that rotate the spark plug's ground strap in 30-degree increments up to 360 degrees, positioning it for better piston dome clearance and a more even burn.
The set includes 24 shims: 12 silver 60-degree shims and 12 black 90-degree shims, along with detailed instructions and a dial chart. For use with 14mm flat seat spark plugs only.
Spec Sheet: Allstar Performance Spec Sheet (PDF) | Instruction Sheet (PDF)
Compatibility: Fits 14mm flat seat spark plugs only.
FAQ
What spark plugs do these shims fit?
14mm flat seat spark plugs only.
How many shims are in the set?
24 shims: 12 silver 60-degree and 12 black 90-degree.
What does indexing a spark plug do?
It rotates the ground strap to a specific position for improved piston dome clearance and a more even burn.
How is this different from ALL96506?
The ALL96506 is a small-OD version of this shim, sized specifically for ALL-PRO cylinder heads.
Does this kit include instructions?
Yes, it includes detailed instructions and a dial chart.

