Engine

8,156 products

Pistons, cylinders, camshafts, pushrods, rocker covers, valve train components, and complete rebuild kits. Athena covers gasket sets and cylinder kits; S&S supplies high-performance internals; MCS fills the routine service parts. Fitment runs from Shovelhead top ends through Evolution Big Twin to Milwaukee-Eight. For a full engine build, cross-reference displacement and compression ratio before ordering pistons.

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Showing 1–48 of 8,156 MOTOR PARTS

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Common questions

Can CVO engine components bolt onto a standard Milwaukee-Eight of the same displacement?

Some can — cam plates and certain air-cooled heads built on the same block architecture often bolt straight across. Others are machine-matched to CVO tolerances that the standard case doesn't meet, and fitting them blind can introduce clearance issues. Cross-reference the part number against the OEM fitment chart for your VIN before buying; a CVO-branded number isn't a guaranteed fit on a non-CVO engine.

How much should I close the plug gap after fitting a 128-inch big-bore kit?

On a high-compression big-bore M8, close the gap to approximately 0.030 to 0.034 inches — the increased compression demands a tighter gap to prevent spark blowout under load. Running the wider stock gap will cause full-throttle misfires even with a fresh tune. Confirm the specific setting with your kit supplier; different combustion chamber shapes affect the ideal number.

What is involved in fitting an Evo oil pump to a Shovelhead engine case?

It's not a bolt-on swap. The Evo pump body uses a different port layout and mounting pattern from the Shovelhead case, so fitting it requires either a machined adapter plate or case machining. It is done, but it's a machine-shop job — confirm the specific case casting number against the pump manufacturer's fitment notes before committing.

Read the full guide: Harley-Davidson Maintenance & Service Guide →

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