So you're wondering why Ford switched the old 289/302 firing order to the 351 firing order for the 5.0?  My supposition would be that after some years of experimentation, and likely input from various racers they found the engine ran inherently smoother and with improved power using the later firing order.

Now as for the Coyote, basically they swapped cylinders 2 and 8 in the old 5.0 order.  Possibly even further testing revealed this configuration even better than the second small block order.  Possibly due to the way other systems on the engine were configured there was an advantage based on intake runner length, etc.  The Coyote is an incredibly efficient engine.  You don't manage to exceed 100% volumetric efficiency if you leave even one scrap on the table in terms of power or efficiency.

When I was young. I had an Uncle that worked at Ford. He was an engineer with development. I asked him why the timing order change. He told me, the 289 order causes a load on the front main bearing, you cannot hear it. When the 351 came out, it produced a front main knock that was slightly audible. So they made the change. When the 5.0 came out the front knock was picked up by knock sensors and kept retarding the timing. They made the change with the firing order and released the 5.0 to the market. 

George wrote:

When I was young. I had an Uncle that worked at Ford. He was an engineer with development. I asked him why the timing order change. He told me, the 289 order causes a load on the front main bearing, you cannot hear it. When the 351 came out, it produced a front main knock that was slightly audible. So they made the change. When the 5.0 came out the front knock was picked up by knock sensors and kept retarding the timing. They made the change with the firing order and released the 5.0 to the market. 

Interesting story, except that the 5.0 doesn't use a knock sensor.
 

I don't consider anything modular to be a 5.0.  I don't care that the new engine has the same displacement.  The new engine is the Coyote.  The 5.0 is the Fox era engine that ran until '95 in the SN95 cars before Ford decided that they should switch to overhead cams.  Frankly, you can have them.  GM and Dodge proved that pushrods still work fine.  A "cam" engine is just out of place in an American Pony Car (427 SOHC doesn't count) IMO. 

If the issue is crank loading then upgrading the main fasteners would have negligible effect on improving the situation.  The issue is how the crank itself is loaded, not any kind of issue with the mains.  I have seen some engines that literally snapped a crank, and the mains were not effected.  Sometimes it would even still run, albeit badly.  I find this explanation a bit troublesome though, because Ford used the 289 in all kinds of racing applications.  Shelby had blown GT350s, and the 289 was used in the GT40s.  I've never read about changing the firing order in any of the books on Ford performance I've read.

By contrast it was known and occasionally done on SBCs where they would swap #4 and #7 in the firing order.  I went back and read up on why guys sometime did that, and what I found was that its basically voodoo.  Some top builders claim it makes more midrange power, others claim it made no difference.  Those who saw power seem to think it reduces bad harmonics, flexes the crank less, or has something to do with what occurs when adjacent cylinders fire in consecutive order.  One thing I read that maybe made some sense was in relation to the intake manifold, when they are tuned, which the 5.0 definitely uses.  But, consider that the firing order swap predates EFI, and it still doesn't explain the 351W, especially when just about every other Ford V8 uses the old firing order.

In the end I think this one is a question wrapped in a conundrum inside an enigma.  There was definitely a reason for it, and the ones given sound as good as any, but I've yet to read anything that's absolutely definitive on it.  I'll muddy the waters further by saying that I had originally heard that on a SBC it was to reduce the chance of an inductive missfire from adjacent cylinders firing in order, with lengthy plug wires leading to them were routed right alongside each other.  This could produce ignition in a cylinder that had fuel, but wasn't ready to fire, and the results could be pretty bad.

351w was the only engine prior to the 5.0L (not Coyote 😜) that had this odd ball firing order.
I think it had to do with the brother-in-law theory...someone’s in-law made a machine to make the cams for 351w.
Or better yet...Ford executives liked the exhaust note better.
Still wondering.

Anyone have engineering proof?

pbrownrk wrote:

Coyote motors have a knock in them I have taken my 2018 F150 into the dealer twice to be checked. The last time they provided a service bulliton that said Mustangs and F150 with the coyote motor have a mechanical noise sounding like knock coming from the passenger side of the engine is common and not a defect. Well time will tell I guess. Not sure I believe it




f150

Is it at engine speed or half engine speed?
 

terry wrote:

TKOPerformance wrote:

George wrote:

When I was young. I had an Uncle that worked at Ford. He was an engineer with development. I asked him why the timing order change. He told me, the 289 order causes a load on the front main bearing, you cannot hear it. When the 351 came out, it produced a front main knock that was slightly audible. So they made the change. When the 5.0 came out the front knock was picked up by knock sensors and kept retarding the timing. They made the change with the firing order and released the 5.0 to the market. 

Interesting story, except that the 5.0 doesn't use a knock sensor.
 

heres the specs for the engine I put in my 65 a few years ago, note under engine description....   but what do I know!!!!!!!!!!!!
SpecificationsFuel TypeGasolineFuel SystemFuel InjectedCylinders8Engine TypeOHV V8Engine Size - C.I/Liters302/5.0TransmissionAuto or ManualVIN TypeF,EInstallation InstructionsPre-lube and Break-In procedure, engine oil and gasket kit shipped with engine. Professional installation recommendedEngine Description1987-1992 5.0L OHV V8; Passenger car, T-Bird, Cougar, Mustang; Roller cam, knock sensor;Head CastE5TE-AB, E7TE-PA, E6SE, F4TY, F0JE-AABlock CastF1SECrank CastE7AE-AA, 2MAE

That knock sensor comment in their description may mean the block or head has capability of installation of a sensor, but I don’t believe Mustangs ever had a knock sensor.  I have a 98 Explorer engine in the shop and it does not appear to have one.

It would not be uncommon for a description such as that one to have a mistake in it.

The EECIV does have the inherent ability to run a knock sensor from a software standpoint, and you will see knock sensor information in the strategy.

That said, no 5.0 used in a Mustang or passenger car ever had one.  They were used on 2.3s and some trucks.  The 5.0 car ECUs literally don't even have the circuitry to allow their use.  Its theoretically possible to add the electronic components to a board that doesn't have them, but it would require a thorough understanding of electrical engineering, and you would have to be able to source the components, which may well now be discontinued, so you may have to find an ECU that has them, unsolder and resolder them into your ECU.  The biggest issue is that you would have no way to properly calibrate the sensor, and aftermarket components like roller rockers may throw off the stock calibration.  Honestly, its mostly theoretical information.  I've never heard of anyone actually using a setup like this.  You'd be better off with a proper tune that keeps the engine out of detonation.

pbrownrk wrote:

TKO
Its at idle. I have had people in parking lots ask me what is wrong with my engine. Rev the engine up and you can't hear the knock.

Hmn, wondering if its valvetrain related, like a slack issue that goes away with RPM, or something else.  Regardless, its BS that Ford does stuff like this.  People shouldn't be asking you if you like your Diesel when you have a gas truck.  Ford just decided that it wasn't a warranty threat, issued a TSB, and washed their hands of it.  Did it always make the noise, or did it start as the engine got some miles on it?

I had also heard the change to the 351 firing order was due to excessive wear on the #1 main bearing due to #1 and #5 firing consecutively.  So, why did they change back to the same scenario firing order on the Coyote?  Any possibility they also changed the way they number the cylinders on the block?  Maybe the different serpentine setups load the crank differently?  Maybe some younger engineer did not research what happens if #1 and #5 fire consecutively since they weren't even born when that firing order was in use?  THAT ONE is my guess...

TKO
Its funny you mention the diesel. I have a 1993 Dodge Cummings Diesel. While My F150 is not as loud it gives me pause every time I drive it and think about the F150. It was not quite as loud when I first bought. It increased some  until about 6 thousand miles.  At 14,000 I drove from Oregon to Iowa and bought a new RV trailer around 4300 lbs. It was winter and snow had followed me across the mountains so I went south to hwy 40 and back up to Oregon. Whole trip about  7 to 8,000 miles with no further increase in noise. It now has 25,000 with no oil consumption or increase in noise. I have about 8 months left on the warranty and while I have never bought an extended one I am thinking about doing that this time. 

Thats crazy and i have never seen that before.  Did the outer part of the front dampener slip causing it to become out of balance too?

BobE wrote:

As I understand the change was made due to loading on the #1 bearing that lead to the crankshaft breaking.
The change didn't help my 86 full size Bronco's 302's crankshaft.
Interesting is that a vibration developed (I assumed the crank had started to crack) and it took a few months driving 50 miles daily back and forth to work before it got real bad and I had to reduce speed.  I did make it home, and below is what it looked like when it was taken apart.  I'm still shocked that it ran like this.