James Gaskets Big Twin Gasket Kit - SET CYL Head/Base 3 5/8 Bore KIT 16770-86-S — Harley-Davidson (1955-2026)

James Gaskets Big Twin gasket kit for 3 5/8-inch bore cylinders, containing cylinder head and base gaskets needed for top-end rebuilds or base gasket replacement. Direct replacement for standard Big Twin V-twin engines.

Features

• Cylinder head gasket included
• Base gasket included
• 3 5/8 inch bore specification

Specifications

• Brand: James Gaskets
• Manufacturer Part #: 16770-86-S
• Weight: 0.156 lbs

Fitment

Fits Big Twin engines with 3 5/8-inch bore cylinders.

Frequently Asked Questions

What gaskets are included in this kit?

Cylinder head and base gaskets — the two most critical seals needed for a top-end rebuild or base service.

Will this fit my engine if I don't know the bore size?

This kit is specifically for 3 5/8-inch bore cylinders. Check your engine manual or existing gasket packaging to confirm bore size before ordering.

Do I need any other gaskets for a complete rebuild?

This kit covers the head and base. Additional gaskets like rocker cover, oil pump, or cam cover may be needed depending on your rebuild scope.

Are these OEM spec?

James Gaskets manufactures these to OEM Big Twin specifications as direct replacements.