Shovelhead Heads Big Bore 3-5/8″ by Speed And Science®. Billet Aluminum (6061-T6) Heads/Intake system for the Harley-Davidson™ Shovelhead models.
- Bolt-on installation for all ’66-’84 models equipped with 3-5/8″ Bore cylinders. Designed to match S&S™ Sidewinder series pistons (P/N 106-5535, not supplied).
- This system achieves very strong torque curve and very respectable HP that peaks exactly where needed.
- Our product is user-friendly and easy to service down the road also. No custom pistons, valves, guides, fasteners, etc. to worry about.
- Fast, very efficient ports designed to make peak power/torque within the useful RPM range. Your bike will pull hard from the get-go all the way up to the redline. The longevity and fuel mileage won’t suffer either.
- Proprietary, super-fast design of the combustion chamber yields 10.05:1 w. 4-1/4″ stroke (10.55:1 w. 4-1/2″ and 10.80:1 w. 4-5/8″ stroke) calculated compression ratio (85CC chambers with Sidewinder pistons). Works well on the hi-octane (e.g. North American 94) pump gas. Compression releases included for easy starting.
- Valvetrain (AV&V and KPMI) components accept up to .625” valve lift, with almost .200” lift before valve-to-valve contact. Using tall camshafts may require an additional machining to provide necessary clearances.
- Increased cooling area drops the head’s operating temperature up to 35F.
- Dual (independent) CNC Billet Aluminum Intake Manifolds (seals included). Carb interface: 41.4MM ID, 2-3/4″ x 5/16″ bolthole spacing. We have completely redesigned the Intake <–> Head interface to eliminate vacuum leaks.
- Exhaust interface accepts both OEM single-bolt flanges as well as the aftermarket three-bolt pattern.
- Hi-tensile steel thread inserts (headbolts, intake, exhaust) installed; all original thread sizes, no need for “special” fasteners.
- OEM oil drain location.
- ***The difference in surface finish between the Intake (coarser) and Exhaust (smoother) ports is intentional.
- Warranty details and conditions are listed in the Installation Manuals ( Manuals download page )