Many older L6, L8 engines are sidevalve, but there are several Types of position and alignment of the valves used. Here's my brief summary.
There are basically four Types of valve seat placement in flathead engines (that I'm aware of), here beginning with the most common.
Type 1: the valve stems are exactly parallel to the cylinder axis (22.5° from vertical in 45° V-twins, 21° in Indians, &c.), and every level of the valve seat (and relief, if present) is parallel to the deck surface (same angles). Relieving is generally indicated to unmask sunken valves.
This Type includes all Indian twins, as well as many automotive engines including the Chrysler 237, 251 & 265, Ply-Do 218 & 230, many lawn mowers, generators & similar industrial engines, but no Harley-Davidson.
Type 2: the valve stems are tilted with respect to the cylinder axis in the fore-&-aft plane (as seen right the side in elevation view), but parallel in the cross-axis. All H-D D, R, W, G, V, & U flathead valves are inclined 4½° from the cylinder axis. The intake and exhaust valves of each cylinder are parallel to each other. Both front cylinder valves tilt forward (27° from vertical), and both rear cylinder valves tilt backward (27°). Every level of the valve seat (and relief) inherits this same angle, and is not parallel to the deck surface. These engines commonly have a machined relief leading from the seat toward the bore.
H-D may be the only representative of this Type.
Type 3: the valve stems are "tilted" toward the bore center in the cross-axis (as seen from the front or rear, or above), but parallel to the cylinder axis in the fore-&-aft plane. The intake and exhaust valves of each cylinder are parallel to each other. Every level of the valve seat (and relief) inherits this same angle, and is not parallel to the deck surface. These engines commonly have a machined relief leading from the seat toward the bore.
This Type includes the Pontiac 239 L6, the Ford V8, but neither H-D nor Indian.
Type 4: the valve stems are tilted with respect to the cylinder axis in both the fore-&-aft plane (like Type 2), and toward the bore center in the cross-axis (like Type 3).Every level of the valve seat (and relief) inherits these same angles, and is not parallel to the deck surface in either plane. The H-D fore-&-aft angles are the same 4½° as Type 2. The intake vs. exhaust angles of these engines differ. These engines commonly have a machined relief leading from the seat toward the bore.
This Type includes the H-D WLDR "Special", WR, K, KH, KR, &c., but no Indian.
This is my own work for Forum use & discussion. Please do not copy, repeat or post this?
