What is the primary benefit of using this kit for a big bore M8 build?

This kit strengthens the top end of your M8 engine, making it more reliable under the increased stress of big horsepower and torque numbers. It replaces key OEM components with stronger, more durable S&S Cycle parts.

What specific components are included in the S&S Cycle Guardian Kit?

The kit includes heat-treated 8640 steel head bolts, forged 8620 steel roller rocker arms, stronger rocker arm shafts, and a rocker arm stud kit. These parts work together to enhance the valvetrain's durability.

Are there any special tools or modifications needed for installation?

The manufacturer states these are direct replacement parts for OEM pieces, which generally simplifies installation. However, for specific tool requirements and procedures, it is always best to refer to the manufacturer's installation instructions.

S&S Cycle 2017 M8 Models Big Bore Top End Guardian Kit

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Specifications

Brand: S&S Cycle
Part #: 900-1092
UPC: 900-1092

S&S Cycle 2017 M8 Models Big Bore Top End Guardian Kit

Name: S&S Cycle 2017 M8 Models Big Bore Top End Guardian Kit
Brand: S&S Cycle
Price: 927.60 USD
Availability: InStock

$927.60

On Backorder — Expected to ship by Apr 17, 2026

Order now to reserve yours — we'll ship as soon as stock arrives. Full refund if we're unable to fulfill.

S&S Cycle 2017 M8 Models Big Bore Top End Guardian Kit. Strengthens your M8's top end for big power builds.

Key Features

Fits 2017 and later Harley-Davidson M8 models.
Heat-treated 8640 steel head bolts offer 200,000 psi ultimate tensile strength, a 14% increase over stock.
Forged 8620 steel roller rocker arms are designed using Finite Element Analysis (FEA) for increased strength.
Includes stronger rocker arm shafts to replace worn or broken OEM parts.
Rocker arm stud kit helps extend the life of your cylinder heads.
Direct replacement for OEM parts, simplifying installation.

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Will this fit your vehicle?

Product Details

If you're building a big power M8 engine, strengthening the top end is crucial. This S&S Cycle Guardian Kit bundles key components designed to handle increased horsepower and torque, offering a more robust valvetrain than stock. It's a direct replacement for OEM parts, meaning it fits right in without major modifications, making it a convenient choice for your high-performance build.

The kit includes heat-treated 8640 steel head bolts with a 200,000 psi ultimate tensile strength, which is a notable 14 percent increase over stock, ensuring your cylinder heads stay securely in place under stress. Forged roller rocker arms, made from 8620 steel and designed using Finite Element Analysis (FEA), offer greater strength and improved durability. You also get stronger rocker arm shafts to replace worn or broken OEM pieces, and a rocker arm stud kit that helps extend the life of your cylinder heads. These components work together to create a more reliable and durable top end for your M8.

This kit is designed to fit a range of Harley-Davidson M8 models, including popular bikes like the Road King, Street Glide, and Fat Boy. It's a comprehensive package for anyone looking to bulletproof their M8's valvetrain for demanding performance applications.