for Flathead

Aluminum cylinder heads for side-valve engines. In air-cooled engines, material with good heat dissipation is of great importance. When heat builds up, it results in power loss. Higher compression is meant to produce more power, but higher-compression engines run hotter. That’s why, starting in 1940, Harley-Davidson equipped the higher-compression side-valve engines (5:1 and above, with the standard being 3.6:1–4.5:1) with aluminum cylinder heads. Aluminum dissipates heat better than cast iron. The heads offered are supplied in pairs.

A few more extra ponies for that old Big Flathead won’t hurt and you will get them fairly easy with a set of these ULR cylinder heads, made from cast aluminum. While looking quite original on the outside they feature an advanced combustion chamber design for improved combustion and breathing. Chamber volume is 100 cc, giving 6.1:1 compression on a 74” and 6.5:1 on an 80” motor. Substantially more material allows for custom milling and pop-up pistons. Another update are the 14mm sparkplug threads (3/4” long) for modern and more common plugs.
Dyno tests showed 18% more power and 13% torque increase over a stock 1946 UL with medium compression heads, just by swapping over to ULR heads! Check out the dyno diagram! These are true rear wheel numbers, power was up big time and torque curve is impressive! Remember, torque is the most important figure with flatheads!

Stock replacement stud and nut kits for 45”/750 cc Flatheads with cast iron cylinder heads.

Stock replacement cylinder head bolt kits for Flatheads with cast iron cylinder heads. For 1929-1950 small 45”/750 cc Flatheads this is a Custom application to replace the stock studs and nuts.

When the factory started to omit the priming cups in late 1936 such plugs were installed to close the existing holes in the cylinder heads. These exact duplicates replace your missing, worn or wrong parts. Of course, it can also be used as a drain plug.