These cylinders for knuckles and Flathead Power KN-Series engines are made of the same engineering-grade grey cast iron that we have used for years in our cylinders for shovel engines. As a result, these cylinders have very high tensile strength and excellent wear resistance. Cylinders are available unfinished and with a durable black powdercoat finish. Available in 3 7/16" and 3 5/8" bore. Different length cylinders are also available. Fits 1941–'47, 74" knuckle engines and Flathead Power KN-Series engines.
Options
- 3 7/16" or 3 5/8" bore size
- Available in sets or single front or rear cylinders
- Available fit with your choice of S&S pistons
Flathead Power cylinders are now "configured to order," which allows customers to order a set of cylinders only, a front or rear cylinder, or a set of cylinders fit with a set of S&S pistons of their choice. In addition, S&S offers machine shop services through the S&S remanufacturing program. New pistons can be fit to your existing cylinders for a reasonable charge.
| Typical Cylinder Dimensions for 1936–’47 OHV Engines & Flathead Power® KN-Series Engines |
| Model Year |
Displacement |
Cylinder Bore |
Cylinder Length |
Notes
|
| 1941-’47 |
74" |
3 7⁄16" |
5.530" |
No Fire Ring |
| KN-Series |
93" |
3 5⁄8" |
5.625" |
No Fire Ring |
| Special |
– |
3 7⁄16" or
3 5⁄8" |
Specify |
You Tell Us! |
| *Cylinders for 61" knuckle engines are not available from Flathead Power®. Cylinders for stock 74" knuckle engines and Flathead Power KN-Series engines do not have a fire ring on the head end of the cylinder. |
NOTES: Flathead Power cylinder heads for 1940–'47 OHV big twins are machined for 7/16-20 head bolts and are not compatible with stock 7/16-16 head bolts. If using FHP heads with 3 7/16" bore cylinders, stock style hex head bolts for 1948–'65 big twins, part #106-4523 may be used. Flathead Power 3 5/8" bore cylinders require the use of FHP 1966–'84 style 12 point head bolts part #93-3024, due to clearance issues.
Stock 1930–'78 hex style base nut kit is available in cadmium plate, part #106-4522, for 3 7/16" bore cylinders only. Stainless raised hex base nuts, part #93-3063-S, are required for 3 5/8" bore cylinders.
