Firing Orders -> Bearing wear.... A Discussion.

[mechanicx]

I meant the old firing order had good reliability at the designed max power output of about 375-400 hp for the classic small block, not so much for just low performance tunes. Although the LS does seem to have a higher maximum design power output, displacement and good reliability.

You have to consider a lot of other things changed that affected durability besides the firing order and classic smallblocks can run up to about the same milage in fuel injected trim with modern oil and unleaded gas.

I'm not saying the revised firing order doesn't contribute to bearing durability especially out high output. But I think something like priority main oiling system could be a bigger factor.

I guess I would go back to my original point that it could be engine specific. A high specific output per liter engine with an aluminum cylinder case and maybe not having an as over built bottom end like some of the classic V8s could suffer more wear with the old firing order. Changing the firing order on a given engine may reduce bearing wear, but how much if any depends on how far on the ragged edge the engine was to begin with I think.

I really don't know that much about BMW V8s but my guess is if they have problems then it's due to bad design and the firing order is the only part of the issue.

 

[OVERKILL]

Originally Posted By: mechanicx
I meant the old firing order had good reliability at the designed max power output of about 375-400 hp for the classic small block, not so much for just low performance tunes. Although the LS does seem to have a higher maximum design power output, displacement and good reliability.

You have to consider a lot of other things changed that affected durability besides the firing order and classic smallblocks can run up to about the same milage in fuel injected trim with modern oil and unleaded gas.

I'm not saying the revised firing order doesn't contribute to bearing durability especially out high output. But I think something like priority main oiling system could be a bigger factor.

I guess I would go back to my original point that it could be engine specific. A high specific output per liter engine with an aluminum cylinder case and maybe not having an as over built bottom end like some of the classic V8s could suffer more wear with the old firing order. Changing the firing order on a given engine may reduce bearing wear, but how much if any depends on how far on the ragged edge the engine was to begin with I think.

I really don't know that much about BMW V8s but my guess is if they have problems then it's due to bad design and the firing order is the only part of the issue.


Fair enough. However, even if we look at the classic smallblock, how many of them have lived as long a life as say the 6.0L LS engine at the same power level? And I mean the modern SAE NET power rating scheme, not the 1960's "350HP 327" SAE GROSS nonsense which makes that the equivalent of around 225HP when converted (roughly).

I just find when you look at the timeline, even since the 80's with injection if you want to start there, that HP/L has increased yet the engines are as durable, if not moreso than their predecessors and the Modular and LSx family, which share things like deep-skirted blocks, bore spacing and their firing order appear to be leading the pack here. I think more rigid architecture plays a role, but I think all these things, including the firing order are cumulative and allow these engines to perform at the level they do and last.

Regarding the BMW "problem".... I'm not sure there is one to be honest. I mean some guys get insane mileage without issue, others.... They end up having to do rod bearings. And there is no rhyme or reason to it. They are even running the coveted TWS 10w60

And of course you've got people saying you need to plan on replacing them at at given mileage and others arguing to the contrary. Perhaps the whole thing is a bit of a red herring or outlier in regards to this discussion, but it was what got me thinking about this in the first place.... So here we are

 

[mechtech2]

Originally Posted By: OVERK1LL
Originally Posted By: mechtech2
Something must be flexing.
The oil is not induced in to the bearing by the firing order, and the loading is the same.
Could be crank or block flex.


Explain please.

Obviously the oil distribution to the crankshaft in no way corresponds to the firing order. However, each cylinder, when it fires, induces a load on the crankshaft. It is the timing of these induced loads that is determined by the firing order. If you have a whole pile of them going off on one end of the crank, that end is going to experience more load.


Sounds like a good valid point. A bunch of hammering at once may cause extra loading.
But I still think flexing is more to blame.
Ever notice how modern engine blocks are buttressed, have stiffener plates, etc.? I know Honda had problems with some of their blocks - it is a very real problem for factory engineers - LOTS of thought goes into this, with computer modeling.
And crank flex? If things add up wrong, harmonics and pressures can surely cause problems. This is why racers use stronger forged and better built cranks.

The bottom line is that if we know there is a problem for those Ford V8s, we now know how to attenuate it.
I certainly don't know for sure what the cause is, and likely may be more than one element.

 

[OVERKILL]

Originally Posted By: mechtech2
Originally Posted By: OVERK1LL
Originally Posted By: mechtech2
Something must be flexing.
The oil is not induced in to the bearing by the firing order, and the loading is the same.
Could be crank or block flex.


Explain please.

Obviously the oil distribution to the crankshaft in no way corresponds to the firing order. However, each cylinder, when it fires, induces a load on the crankshaft. It is the timing of these induced loads that is determined by the firing order. If you have a whole pile of them going off on one end of the crank, that end is going to experience more load.


Sounds like a good valid point. A bunch of hammering at once may cause extra loading.
But I still think flexing is more to blame.
Ever notice how modern engine blocks are buttressed, have stiffener plates, etc.? I know Honda had problems with some of their blocks - it is a very real problem for factory engineers - LOTS of thought goes into this, with computer modeling.
And crank flex? If things add up wrong, harmonics and pressures can surely cause problems. This is why racers use stronger forged and better built cranks.

The bottom line is that if we know there is a problem for those Ford V8s, we now know how to attenuate it.


Interesting point:

the Windsor and the SBC were very similar in terms of how the bottom-end was designed.

Likewise, the Modular and LSx are very similar bottom-end wise.

the difference, in both cases, is above the deck.

The LSx is basically (mechanicx, don't hate me) a Windsor with a heavier, deep-skirted block. Even the heads bolt on

The Modular is very similar in this regard, except with narrower bore spacing (for reasons that don't need to be delved into in this thread).

Both have VERY heavy duty bottom-ends compared to their predecessors.

SBC or SBF, both can readily be built to make plenty of jam. "block limit" for the late thin-wall casting SBF is around 650HP with a blower (just north of 500RWHP roughly).... beyond that, you risk (and some still do) splitting the block. The limit is higher with a turbo. 600+RWHP. The older blocks from the 60's (including the 289) and early 70's were much stronger. And that block was made for some time longer in Mexico (hence the lust for "mexican blocks" when building a Windsor).

IIRC, the same limit applies to the roller SBC, which wasn't as heavy duty as the old castings from the 60's and 70's.

However, what is the longevity of the engines at this power level? I have no idea.... but I'm sure it is no where near how long the Shelby's 550HP Modular will last, the 440HP BOSS 302, the 505HP LS7 or the new LS3.

It is like we've "level'd up".....

You can slap some hair dryers on an '03/'04 Cobra and make 1000HP. What's the limit of the new ZL1? I'm sure right there as well. What engine from the 80's could handle 1000HP stock?

And while I seem to have derailed a little here, my point is that the cumulation of these advancements have allowed us to RELIABLY make power at levels that before required a whole pile of engine work and weren't expected to last 150,000 miles. And I think this firing order.... And the reason it is used, may play a role here.

 

[mechanicx]

I know what you're trying to do here Overk1ll. You're trying to insinuate Ford's Windsor design was the cat's meow. Nope, nope, nope

.

 

[OVERKILL]

Originally Posted By: mechanicx
I know what you're trying to do here Overk1ll. You're trying to insinuate Ford's Windsor design was the cat's meow. Nope, nope, nope

.


God no! though I know, given our history, you might think that way

I'm thinking that they may have, when trying to come up with a solution to the high mileage bearing wear occurring more on cylinders 1/5, accidentally come up with the "best" firing order and simply started using it on everything from that point forward.

GM wasn't having issues (and really, neither was Ford, they continued to use the same firing order as the SBC on the lopo Windsor right through to the 90's, and the same firing order on the 460 IIRC) but when they were going clean-slate, they decided to use the same firing order as ford because it just made sense at that point.

 

[Ben99GT]

What I don't get is why the new 5.0 went back to the flathead firing order?

 

[ms21043]

A big reason GM went with the firing order they did with the LS engines was for spark and injector timing accuracy. They wanted the reluctor wheel closest to the spot on the crankshaft where torsional vibration is minimal. On LS engines that's just ahead of cylinder 7 centerline, torsional vibration is zero in that location. With the old SB firing order you would have more torsional vibration.

On older engines with distributors, timing was always off a few degrees between cylinders because of the torsional vibes the cam and crank fed into the distributor. With the LS, almost perfect timing makes for a more efficient and smoother running engine.

 

[OVERKILL]

Originally Posted By: Ben99GT
What I don't get is why the new 5.0 went back to the flathead firing order?


They did????????????? That's news to me!!

 

[Ben99GT]

Originally Posted By: OVERK1LL
Originally Posted By: Ben99GT
What I don't get is why the new 5.0 went back to the flathead firing order?


They did????????????? That's news to me!!


Yep, the new 5.0 went to 1-5-4-8-6-3-7-2 with the usual Ford cylinder numbering.

 

[OVERKILL]

Originally Posted By: Ben99GT
Originally Posted By: OVERK1LL
Originally Posted By: Ben99GT
What I don't get is why the new 5.0 went back to the flathead firing order?


They did????????????? That's news to me!!


Yep, the new 5.0 went to 1-5-4-8-6-3-7-2 with the usual Ford cylinder numbering.


That's the Y-block firing order, not the flathead according to the chart (which shows the flathead as f'd up anyway).

Which is the same as BMW............

So BMW is "right"? LMAO!!

That puts a whole new spin on things sir........

 

[Ben99GT]

Originally Posted By: OVERK1LL
Originally Posted By: Ben99GT
Originally Posted By: OVERK1LL
Originally Posted By: Ben99GT
What I don't get is why the new 5.0 went back to the flathead firing order?


They did????????????? That's news to me!!


Yep, the new 5.0 went to 1-5-4-8-6-3-7-2 with the usual Ford cylinder numbering.


That's the Y-block firing order, not the flathead according to the chart (which shows the flathead as f'd up anyway).

Which is the same as BMW............

So BMW is "right"? LMAO!!

That puts a whole new spin on things sir........


I guess so!

Regarding flathead firing order...

 

[OVERKILL]

Originally Posted By: Ben99GT

I guess so!

Regarding flathead firing order...

OK, so MSD's chart is screwy and the Y-Block and Flathead share the same firing order......

Which is the same firing order as BMW uses.

Oh boy.

 

[OVERKILL]

I feel I need to add that the rod bearing "issues" that I've seen pictures of with the S62 show even wear front to back.

Which is unlike the wear I've seen on the old (lopo only) Windsors, and IIRC, the odd SBC, which showed more bearing wear on 1/5 and 1/2 respectively.

Keep in mind, we are talking VERY high mileage engines here. It is more of an observation than it is an "issue". But this most recent development really does have me questioning what the logic is behind going back to the Y-block/Flathead firing order, if, as I'd indicated, Ford's whole reason for going to the other firing order (though not from this one) was (and is reinforced by the statements that mechanicx quoted from GM) that it was more "balanced".

We need some engineers from Ford and BMW in here STAT!

 

[mechanicx]

I was just going by what you said about the BMW firing order because I assumed you knew what you were talking about

. J/K The firing orders with different cylinder numbering are confusing for me too and I'm too lazy to check them. I have to look at everything compared to the SBC firing order.

Ford has changed firing orders a lot and been back and forth on the firing orders. Just like Ford, can't make up its mind lol. My recollection is the flathead and Y-block had a "4-7" swap and the Windsor and LS swap 4-7 and 2-3. Supposedly the 4-7 swap gives torsional advantages as well. But I don't know why they would change away from the Windsor and Modular firing order.

 

[OVERKILL]

HAHAHA, if I knew what I was talking about, we wouldn't have this thread! LOL!

But I do find this topic somewhat fascinating

Likely due to the fact that we simply don't know all the reasons behind this.

 

[Ben99GT]

I wonder if the Y-block/Coyote/S62 firing order was proven "better" for high RPMs?

I can't think of another reason for Ford to make the switch on the new 5.0.

 

[mechanicx]

It's possible the flathead firing order made a couple more HP and TQ through the powerband than the Windsor/modular firing order. The 4-7 swap on classic Chevys is somewhat popular in racing and is thought to pick up a few HP and slighly reduced crank harmonics. And maybe there was no crank load advantage to the modular firing order over the flathead anyway. I think the crank load is not really a big issue anyway.

It could also have something to do with where the crank sensor is located. Someone else in this thread said that GM swapped firing orders to the modular order on the LS because there would be zero torsional at the crank sensor location. I think the coyote has the crank sensor at a different location and at the rear of the crank. I don't know what difference the firing orders might have made if any there.

 

[mechtech2]

Another reason for wear at #1 bearing is the cam chain dancing around.
This one has nothing to do with the firing order.

 

[OVERKILL]

Originally Posted By: mechtech2
Another reason for wear at #1 bearing is the cam chain dancing around.
This one has nothing to do with the firing order.


True, though as I've said, you don't get more wear on 1/5 in the Windsor with the HO/351 firing order; the engine wears evenly.