Ford Shelby GT350 Mustang Flat Plane V8 Explained

You didn't mention firing order and exhaust note.

I can't see how there'd be that much of a difference other than engine block length between a flat 8 versus a Subaru boxer 6. What would be the difference between this Ford engine and Subaru slapping two of their boxer 4 engines together? And as for engine vibration, Subaru's have nearly none.

Or are they not making it a horizontally opposed engine?

Ford has a long history of building flat plane V-8's for Formula 1. When the Ford-Cosworth DFV (double four valve) came on the scene in the late 1960's, it became the engine for a team to run and win. I think they were still winning world championship events with this engine all the way into the early 1980's in Formula and other racing platforms like sports racing.

Flat plane V-8's sound exactly the way you expect a real racing engine to sound. An old Ferrari 308 QV with a track exhaust sounds great. I can't wait to hear audio of this engine when somebody puts it on the web.

The cost comment on the engine seems a bit off. A flat plane crankshaft, in production numbers, will cost less to produce than a splayed/cross-plane crank as it is a simpler piece. The differences in the camshafts will be negligible. The rest of the parts are on par, although the pistons and rods will need to be lighter. The actual production cost for the entire assembly might not be much more at all, if any, than the standard Coyote.

I've seen a picture of the new crankshaft and it seems wholly unconventional- Typical flat plane V8 crankshafts look like Inline-4 crankshafts with wider crank pins, that is to say, pins 2 and 3 are at the same angle, and pins 1 and 4 are at the same angle. Thus, the outer pistons move together and the inner pistons move together, eliminating any rocking motions along the axis transverse to the engine. The crankshaft I've seen for the GT 350 however shows pins 1 and 3 at the same angle and 2 and 4 at the same angle, which would create a rocking motion in each cylinder bank. Anybody know what's going on here?

I'm way late commenting on this, but this flat plane V-8 gives me concerns. First the best way to eat up main bearings is to unbalance the crankshaft. This design is going to sound exactly like two inline 4-cylinder engines sharing the same exhaust. The claim of quicker revving ability may be true for first gear only, where the engine revs up so quickly. It would not be noticed in higher gears. I have heard 5.0 Mustangs rev in neutral and they go from idle to redline in less than a second. As for mounting the engine lower to the ground, shaving the counterweight diameter down might allow 1/2 inch. The reason this racing flat plane design is not used in street cars is not exotics or performance.... this crank is cheaper than a cross plane crank. It's to save $$. Ford actually spends great effort shielding this engine's vibrations from the frame and body. Lastly, I heard the stereo system actually plays a standard good-sounding V-8 sound over the speakers when this thing accelerates. I'm blaming this on the new European Ford Brass that have no clue what American drivers want in sports car engines and sound.

drive a new GT 5.0 and a GT350... they are in the same shape body car, other than that wow, sound, response, handling, etc are both great BUT different... I must admit to making involuntary giggling noises in the GT350. I think it is a shame that the dealers put a premium on what otherwise would be an affordable option to Italian sports cars and on par with high end Corvettes...the performance is amazing and the sound doesn't need any help, it is killer on its own lol...I have had a few Corvettes but would not hesitate to have my car's logo match the one on the trucks I have always owned. In the 60s etc we raced Chevy's (mostly because the parts are cheaper and interchangeable)i.e. Ford had three 351s that all used different parts? (W, C, M) but we pulled our race cars with Ford pick ups! You might find a GT 350 at the honest price as they should be easier to find when the GT500 takes the spotlight...

The cross plane V8 needs big balance weights as it produces a rocking couple. The back of the engine goes down as the front rises, 180 degrees later the front drops and the back kicks up.

A flat plane V8 with conventional up, down, down, up crank has perfect primary force and couple balance. It has a secondary force out of balance at 2x engine speed that is 1.4x bigger than a single bank. The only way to balance 2ndry forces is by use of balance shafts a la Porsche 944/968. There are internally balanced couples that bend the crank, these are balanced by balance webs so the crank runs straight. A major problem is that even without the balance webs the engine will run with exactly the same vibration as it does with them. As the couple is internally balanced it is impossible to balance these couples using a dynamic balancing machine, they have to be precisely calculated and adjusted for any change to piston and con rod mass. There is a distinct risk that the aftermarket will produce lightweight cranks that wipe out the main bearings due to crank bending, this would soon give the engine a bad reputation with tuners.

Ford's flat plane crank is unconventional, up, down, up, down, this reduces bending of the crank. It has perfect primary force balance and the same 2ndry balance as conventional flat plane crank. There are 2 unbalanced couples that add to give a large unbalanced couple. The unbalanced couple is about 2/3rds the size of the couple in a cross plane V8. This reduction allows the crank to be fully balanced by internal counterweights at front and rear with neutral balance pulley and flywheel. As the crank produces an external couple it can be balanced for changes to piston and con rod weights on a dynamic balancing machine by any shop that can balance a cross plane crank using exactly the same method.