The Ford Model K had a somewhat unusual firing order, 1-2-3-6-5-4. This was actually the second most often used six cylinder firing order in 1907, but today is considered unusual, and a few Model K owners have changed the firing order of their cars.
My question is, what do forum members think who are interested in this question? From personal experience with two Model K motors, they run very smooth, however, on both engines, the number six cylinder runs much too rich. Another Model K owner says his number 1 cylinder also runs rich. A third K owner believes the problem is the firing order.
Personally, I suspect a major problem is the early carburetors, along with long, straight intake manifolds. The distance mixture must travel to reach the outside cylinders is more than twice the distance the vapor travels to reach the middle cylinders).
Ray Bell, in 2007, wrote the following in response to a question about the firing order of the Ford on another forum. I don't know Ray Bell, or his background, but he offers an interesting theory:
So, any validity to the idea that this firing order was an early response to the problem with six cylinder "crankshaft whip" or "torsional vibration?" Were Henry Ford and C. H. Wills aware of the straight six vibration problem, and addressing it before vibration dampers?
My for what it is worth.
Years ago, when I was doing some research into early cars, I ran across some information of one of the early theories of engine design. The theory was basically that power transferred through the engine better when the cylinders fired from front to rear. The idea was that each successive cylinder firing added better to the previous cylinder better by doing that. This often seemed to conflict with balancing issues, and vibration was a big problem. I saw and read part of an article (early, maybe as early as '05) discussing the advantages and disadvantages of various firing orders. I wish I had a copy of it I could find. The article was mostly about four cylinder engines. Which is better? 1-2-4-3 or 1-2-3-4 or 1-3-2-4 and so forth.
One of the points I remember was the writer's belief that cylinder order mattered in regards to properly adding one power stroke to the next, and that they worked better in a front to back order, then restarting back again at the front. That belief, that theory, was later disproved.
However. That firing order could have some advantage on crankshaft weight (as Ray Bell whom I do not know either said). It could, or maybe not, reduce the flex stress to the crankshaft that way. That could allow a lighter crankshaft.
As we know today, harmonics plays a much larger role than they would have believed then. And the harmonics change with rpm, as well as has a great deal of influence on balance and vibration. We know today, as some knew then, that more main bearings help a lot. I wonder when the first seven main bearing six was built? I have worked on a few, and love them! But it has always been a judgement call, cost versus benefit.
Chevrolet used a three main bearing crankshaft from 1929 until about '33 (I don't recall the exact year). Even though the crankshaft was quite stout, they had serious troubles with them "flattening out" despite that they had a more standard firing order.
Offhand, I do not recall what the firing order was on my '15 Studebaker six. But I think it was a more standard mixed order. By then, that earlier theory had been disproved.
Nothing much really good from me this time. Just an old theory long since dis-proven.
But maybe part of it could have played into what Ford was working with. We always need to remember that this stuff we take for granted knowing today, was not known then. Henry was figuring it out. He was one of the leading automotive engineers in the world at that time. And even he had to be wrong once in awhile.
Drive carefully, and enjoy, W2
Wayne tells and confirmed what I learned 40+ years ago during my college time studying the engine construction and firing order.
The firing order as we know it now are set this way for crankshaft balance, vibration and specially the torque stress during running.
It results in much lighter construction of the crankshafts.
Just for what it is worth.
Thanks guys. The K crankshaft doesn't seem small in my opinion, and with seven mains, seems well tethered. However, "crankshaft whip" or torsional vibration evidently was/is a big problem with six cylinder (maybe straight eight too?) engines. I know Henry Ford worked on the six cylinder engine as early as January 1904, and enlisted outside help in addition to Wills work. The Ford six cylinder racer had a massive bore/stroke (6/6) and it appears a high rpm (for the period) so I suspect he was doing everything possible to address crankshaft issues.
Thanks again for your responses.