FE Firing Order

[Autoholic]

I was thinking about various firing orders and it crossed my mind that this diagram below has to be incorrect. You can't fire cylinders 1 and 5 in order, they share the same rod journal. What am I missing?

[Joe-JDC]

Same issue on #3 and #7.  #1 fires, #5 will be on exhaust stroke.  Joe-JDC

[runthatjunk]

Cylinder are 90deg apart and motor fires every 90 deg.  No reason it can't work, at least every ford I've owned seems to do ok with it.

[Autoholic]

True. I forgot to include the rotation of the crank needing to match the placement of the block and being opposite banks when possible. I tried to come up with a balanced firing order but it would require a flat plane crank or require a straight 8 block.

[Cyclone03]

Just for fun,the new 5.0 has the same firing order of the flathead V8.

[WConley]

deleted - duplicate post...

[WConley]

Just for fun,the new 5.0 has the same firing order of the flathead V8.

Yeah but is the Coyote's crankshaft offset 0.265" away from the thrust side like the old Flathead?  Chew on that one for awhile Autoholic.  There's a good reason ole' Henry's boys did that...

[Heo]

 

[Autoholic]

Well Bill, the only reason I can think of is the way the rods act on the crank. On one side, the rods push towards the side of the block. On the other side, the rods push towards the oil pan. So a side load vs a vertical load, that ends up more in the direction of the main bolts. That's all I can think of. If you know the reasoning, please share it.

[WConley]

The Flathead is an example of a "Desaxe" engine:

https://en.wikipedia.org/wiki/Desaxe

The reason for this is that as the power stroke starts, the rod is already "over-center" on the crank and is able to create torque earlier.  Some modern engines do this, especially the Atkinson cycle engines used in a lot of hybrids.  There are disadvantages, such as the max piston speed being different on the up-stroke vs. down-stroke, which creates a bit of unbalance.

For a low-speed engine like the Flattie, this worked well.  Modern high-speed engines generally see less benefit from an offset crank, because you can get the same benefit from ignition and valve timing tweaks at higher revs.  The aforementioned Atkinson cylce engines generally run in a narrow powerband, and are optimized to squeeze every bit of efficiency possible.

[Autoholic]

I learn something new every day Thanks for the info Bill.

[cjshaker]

I've been around flatheads all my life and never knew this. Great and interesting bit of info, Bill. Thanks for that.