Overhead Valves are where it's at

[Greg Myers]

[Eshaver]

Ya need to post this overt the H A M B .............. I bet you can get the Chevy guys mad at ya ...................

[bpletcher55]

LONG LIVE FLAT HEADS!

[o-man]

DOHC for the win!

[Greg Myers]

LONG LIVE FLAT HEADS!

Made me laff

[FordRodnKustom]

Well, time sure proved Wally's theory wrong!

[Greg Myers]

Well, time sure proved Wally's theory wrong!

[MachinistMark]

Flatheads are junk. Obsolete before the first one was even built.

[Longbox55]

I'm a Chevy guy, and I'm actually amused by this. Remember Chevrolets slogan; Valve In Head, Ahead In Value.

[philo426]

Flatheads are harder to rebuild,

[Jantrix]

This is a very interesting panel. Note the WW2 war trophies on the wall. Many early hot rodders were vets returning from service. This must be depicting such a person.

[Longbox55]

The valves are in the block, rather than the head. It makes for a much cheaper and simpler engine, but they do have drawbacks in the design. The main drawback is the poor breathing of the engine, as the ports have to be run through the block rather than the head, which only has the combustion chamber, spark plugs, and water jackets in it. On inline Flatheads, it's not as much of an issue, as the parts are pretty much a straight shot, but on V8 engines, the exhaust has to make a 180 degree turn to get to the ports. This not only restricts the flow, but it also tends to hold heat in the block. Overhead valve engines are much more efficient, and will make more power for the same displacement, but are more expensive to manufacture and are a more complicated engine.

[Greg Myers]

Can't wait for this to come out .

[Guest Johnny]

Flatheads are junk. Obsolete before the first one was even built.

Some people are just afraid of a little challenge.

[Art Anderson]

The valves are in the block, rather than the head. It makes for a much cheaper and simpler engine, but they do have drawbacks in the design. The main drawback is the poor breathing of the engine, as the ports have to be run through the block rather than the head, which only has the combustion chamber, spark plugs, and water jackets in it. On inline Flatheads, it's not as much of an issue, as the parts are pretty much a straight shot, but on V8 engines, the exhaust has to make a 180 degree turn to get to the ports. This not only restricts the flow, but it also tends to hold heat in the block. Overhead valve engines are much more efficient, and will make more power for the same displacement, but are more expensive to manufacture and are a more complicated engine.

Of course, for both simplicity and cost reasons, Ford laid out their flathead V8 with simple log style exhaust manifolds, each bank of cylinders being scavenged through a manifold very similar to that of an OHV engine. Trouble was, that meant that the exhaust passages, given that on any ordinary V8 engine, the camshaft lays between the cylinder banks, actuated valves that are on the high side of each bank, with an exhaust passage that went through about 9" of coolant to get to the outside of the block. The result? BEST water heater Detroit ever made! (but they did work and work pretty well even so).

Ford wasn't the only automaker to produce flathead Vee engines: Cadillac, Packard and Lincoln all did (among others). The major difference was (besides the practice of most other automakers to build assembled Vee engines having cylinder blocks bolted to a common cast crankcase) was to route exhaust gasses out the high side of each cylinder bank, giving the shortest exhaust passages, that didn't run through the water jacket. This necessitated a system of multipiece exhaust manifolds. Generally, the left side manifold had its outlet at the front of the engine, with a cross-over pipe (cast iron also) connecting from that to the front of the right side manifold, where its gasses joined those coming out of the right side cylinder bank, then exiting the right side manifold at the rear, as a single pipe system. Those were very expensive to produce, as they had to be very precisely cast, and then precisely machined at their mating points in order to get a tight system with no leaks.

This was the practice of Cadillac V8's from their first one in 1916 through the 1948 model year (Cadillac introduced their first OHV V8 in the 1949 model year--the first series Cadillac V16 and its companion V12 having been OHV, while the second series Cadillac V16 was a flathead engine), Packard did not produce a true OHV engine until they introduced their first V8 for 1955, and Lincoln's Model L (like the MPC 27-28 Lincoln kits) and the subsequent Model K and KB V8's used this multi-section exhaust system, but the Lincoln V12 produced from 1935-48 was laid out exactly like the Ford flathead V8, and had almost all the same characteristics, including a tendency to overheat.

Art

Edited June 10, 2013 by Art Anderson