Shim-Dex shims rotate the ground of the spark plug at 30˚ intervals

anywhere within 360˚

Indexing your spark plugs increases power and provides crucial clearance between the spark plug and piston.

You won’t have to buy extra spark plugs to have them perfectly indexed AND Shim-Dex shims are REUSABLE many times over.

No Frame
No Frame

Model 14F - for 14mm flat seat spark plugs only

No Frame

• Minimal or no thread exposure in the cylinder

head that can overheat and cause pre-ignition

• Shim-Dex shims are so thin they will not adjust

the gap too far out of the combustion

chamber and negatively effect


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