I just read where Ford has built a 5.2L flat plane V8 for the 2015 Mustang GT 350. It will use a crank where all rood journals are on a 180 degree plane and two cylinders will always fire at the same time. Humm. The same design crank is found in a Model T; just half as many cylinders and rod throws.
A flat crank V-8 is essentially two fours on a single crank. There are 4 separate power strokes per revolution, not two. Many early V-8s had this set-up, including (I believe) Cadillac and Lincoln. I had a 1916 Briscoe with a flat-crank, overhead-valve V-8.
True others have used the design, particular in early autos, but this one makes over 500 horsepower and Ford claims it is their most powerful naturally aspirated engine they've ever released in a street production vehicle.
Flat plane V8s have a very distinctive and cool sound... they're used a lot in exotics like Ferrari.
The disadvantage is the balancing. http://www.autozine.org/technical_school/engine/smooth4.htm
I understand that both the Volvos and Mercedes presently racing in Australian V8 Supercars use flat plane cranks and have their origins in cars presently in the marketplace. Although they are raced as 5 liter capacity engines the Volvo is stretched from 4.4 liters and the Merc is shrunk from 6.3 liters.
The sound they make is different to the Fords and GM's but is just magical to hear when they are really revving hard.
Wills Sainte Claire flat plane V-8 crankshaft with added counterweights and adapted to a Model T Ford block.
What's the advantage?
It's explained in Derek's link above.
"Flat-plane V8 for high performance cars.
However, the disadvantage of cross-plane V8s is also about the counter weights - not only increase the weight of engine, they also contribute to rotational inertia, thus making the engine less responsive and less revvy, dropping upper rev limit and top-end power. Moreover, the larger counter weights usually requires a larger crankcase to house them, thus raising the height (and more important, center of gravity) of the engine. Therefore Ferrari all V8 models, TVR Cerbera AJP V8 and Lotus Esprit V8 employ flat-plane V8s instead."
Back about 1960 I knew of a couple of these cranks in racing engines. We called 'em crossfire cranks. I believe the idea was to be more competitive with the Offy engines which really excelled when the track was wet and "heavy".
The guy I pit crewed for on his modified racer had a crossfire flathead Ford in his sportsman car. Also some guy had one in a small block Chevy.
As I recall, they performed right well but what I remember most was, the pairs of cylinders didn't fire exactly together but were a few degrees apart. This gave them a sound that would make your hair stand on end.
Wish I could hear 'em run again.
If the cylinder banks are at 90 degrees, the firing will be very even. If they're at some shallow angle, I should think the sound would be like four Harleys.
Hey Ricks this whole topic really interested me so I read up on it a bunch. All of Ferrari's V8's are flat plane cranks. Another forum I'm on a former Ford engine engineer explained:
A flat plane crank engine will rev to the moon. 8,000 rpm should be no big deal. With it being like two 4 cylinder engines mated to a single crank, each bank sees an event every 180*, the runners are all the same length, the pulses all the hit the collectors at even intervals, and you don't have any weak cylinders. You can now make stupid power.
I believe the GT350 will make something like 560+ HP, and that's just naturally aspirated. The 2014 GT500 made 662 HP but that was with a supercharger. The GT350 will be much lighter and more no-nonsense. It's really cool to see Ford delving into the supercar realm but keep things affordable.
I was just reading the article on Ed Winfield posted on the NWVS site and found this little tidbit relating to flat plane cranks. Given Ed Winfield's relationship to model Ts, this is a nice circle back:
any more info on how a T runs with one ?
The Gentry V8 for Model T's had a flat-plane crank.
Jay, I went back and looked at the thread mentioned by Derek. We had a newbie put some canned C-Rats on a Huey engine deck because he was told meal time would be when he got to the next outpost. Trouble is they forgot to tell him to put a small hole in each can to relieve the steam. Sure enough the cans began blowing just as they were arriving at the outpost and after landing when the guy opened the engine doors, the crew knew right away happened. The unopened V8 vegtable made me think of this tidbit.