Firing Order (Engine Builder Tech)

First let me say I'm not much of an engine builder, but want to get educated here....

I've always read that the Flathead and the Y-block Fords have a pleasant sound because of their "unusual" firing order: 1-5-4-8-6-3-7-2. I know SBC and small block Mopars use 1-8-4-3-6-5-7-2.

Is firing order arbitrary according to the manufacturer? Is one order preferable to another? In fact, does firing order make an engine sound different from another engine with another firing order? And does firing order have an effect on horsepower, power curve, torque, etc?

Does firing order make a difference?

Now, of course, I understand that you can't just go changing the order because the rest of the rotating assembly wouldn't jive. But do some engines have an inherent design advantage from the get go over others because of firing order, just like some motors have an advantage because of their bore and stroke characteristics?

Thanks for the instruction here.

 

one difference is that Fords use wierd cylinder numbering....so even if the orders are the same, the firing order numbering is different.

 

The most forward cylinder/connecting rod isn't always counted as #1??? What are the ways that different engines count cylinders? I didn't realize this difference, Jim.

 

ford V8s count from the front right, 1234 down the pass side, then the driver side front is 5, goes back 678 to the rear.

Normal companies used 1357 from front to back on driver side, 2468 on pass side. Some motors like Pontiacs have 1 as front driver side but the pass side is the forward bank (so if you go from the front of the engine, looking at the crankshaft, it's numbered 21436587)

 

OK, so to "normalize" the cylinder counting on a Ford (with the most forward bank being #1 and going back and forth between sides) I've translated the Ford order to:

1-2-7-8-4-5-6-3

And SBC and Mopar are:

1-8-4-3-6-5-7-2

Is one order "better" than the other? My uneducated observation is that the Flathead/Yblock order moves from the outer cylinders to the inner, while the SBC and Mopar alternate.

 

Buick Nailhead (at least my 401) is 1-2-7-8-4-5-6-3 and #1 cylinder is the front jug on the passenger's side and #2 as the front cylinder on the driver's side.

As I recall, every engine I've worked on has #1 cylinder labeled as the cylinder that's nearest the front of the engine.

 

You are kidding me? So it turns out that if you "normalize" the way you count cylinders on the Flathead, then it shares the same firing order as a Nailhead??? Whodda thunk? After all I've read about how different and unique the Flathead order is, it turns out it shares the same with another legendary hot rod motor. Learn something new every day....

 

If you map out the 2 they don't seem as far off as you would think and think outside the box a little. The last cyl on the chev to fire is #2 so really you have 3 of the outside corners on the Chev firing in order where as the Ford has all four firing. An observation that I would make on the Ford is that the flathead has extra long runners for the exhaust on the outside corners, so firing all of the outside corners first, then the inside group might have an advantage for breathing. I would assume that to some extent the OHV engines then would have the advantage that they could use the firing order for better rotating assembly balance? Of course that's just a guess.

 

For the most part all that matters is that a cylinder fires every 90 degrees of crank rotation.
That said, we used to run a fuel powered flathead dragster in the early 60's with a crank that fired every 180 degrees. It idled smooth and made good power.
Several people have cams ground that swap cylinders 4 and 7 in the firing order and with a set of tri-y headers pick up about 30 HP on the top end.

 

Aaggie, so it would appear that firing order does matter, and that there is a way to optimize what that order would be. Any thoughts/ideas on that? On the flatheads, when you swap the 4 and 7 order, any adjustments in the crank and other rotating assembly? You've already mentioned the adjustment to the cam.

 

440roadrunner, this is my question, what you raised here. After success with the flathead and the Y-block, why did Ford change the firing order in their next series of engines to what the Chevrolets already had? What specifically about that firing order made more "sense?"

Anybody know? I certainly don't, but you engine gurus must have an idea.

 

However, the flatheads and 'Y' block Fords used the same firing order as the recently popular 4/7 swap cams for small block Chevys (when you map it out). BTW, MN Falcon, #2 cylinder is not the last cylinder to fire - a firing order can start and stop anywhere in the designed sequence. Draw up 2 or 3 sequences in a row, then map out an engine block with factory cylinder identification numbers, you'll notice the back cylinders fire sequentially, then the front two, then the middle four on the the flathead and 'Y' block and 4/7 swap engines.
Oh, FYI the '49 to '64 Olds engines all came factory stock with the 1-8-7-3-6-5-4-2 firing order, the 4/7 swap was built in!
The exhaust sound has more to do with compression, cubic inches, cam timing and exhaust system design than firing order.

 

So we are back to the same question and nobody has answered it yet:

Why the 1-8-4-3-6-5-7-2 firing order?

What is it- specifically- that makes this order optimal for modern overhead valve engines? What did the engine gurus discover and make them switch from the earlier order?

I dunno. But somebody on the HAMB does...speak up please.

 

It makes it so the two cylinders closest to the steering box are most likely to suffer from crossfire, and they're a bitch to get to.

You gotsta understand how car designers think

 

Crankshaft design determines firing order. The common 90 deg. crankshafts employed by most V8's were designed to eliminate the 2<SUP>nd</SUP> order vibrations that plaque 4 cylinders. Because these 2<SUP>nd</SUP> order harmonics are eliminated, the life of the engine is greatly extended. Unfortunately the 90 deg. crankshaft is much heavier and more complex than the less common 180 Deg. crankshaft. 180 deg. crankshafts are often used in racing applications to reduce weight and increase the RPM limit. Since there are no counter weights on a 180 deg. crank, they are lighter and easier to manufacture. The 180 deg. Norden crank for a flathead changes the firing order to 1-8-3-6-4-5-2-7 and is 25 lbs lighter than a standard crank. Unfortunately (or fortunately depending on your point of view) your cool 180 deg flathead will now sound like 2 4 bangers coupled together.
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One more point to ponder. International V8&#8217;s have the standard 1-8-4-3-6-5-7-2 firing order, but are timed off the #8 cylinder. Why???<o></o>

 

FrozenMerc, can't you theoretically time the engine off any cylinder as long as you knew where it was in the compression/exhaust stroke??? Is that the answer??? Did I win anything?

 

On normal V8s you can time them off of 1 or 6, but Internationals are just plain ass-backwards.

 

No, because the timing marks on the pulley only line up with timing pointer correctly only when the designated cylinder fires. Timing off any other cylinder, and the light will fire with the pulley "off" by 90 or 180 deg.

 

now just to throw another at ya remember olds motors are 18436572 but fire backwards counter clock wise.

 

Well, duh. Just kick me. I should know that about the timing marks, FrozenMerc.

So the answer to my question about firing order has everything to do about crankshaft design and eliminating harmonic vibration? The modern firing order is superior in doing that? It would lead to greater reliability, although not necessarily greater horsepower? Did I get that correct?

You, sir, are an engine master, if that be the case. I salute you.

 

(My take on the "odd Ford firing order"....)

Old Henry was so stuck on his trusty bangers (4 cyl) that he decided to make a V8 instead of the "more traditional" (at the time) 6 cylinder engines used in other economy minded makes of the day.

In making the jump to a V8, he told himself (and others) that his V8 was essentially just 2 4 cylinder engines. By doing so, he was able to save face in his far too long defense of his trusty 4s...

I think that this was the reasoning behind the "odd" numbering od Ford V8s, as well as the two water pumps, unorthodox distributor, etc.

 

Plymouth 1952: the Olds motors you refer to are 1965 and up. It is the distributor that runs counterclockwise, the firing order is still the same. FWIW, the 'B' and 'RB' Chrysler engines run their distributors CC with the 1-8-4-3-6-5-7-2 sequence. DO NOT try to wire your distributor cap clockwise on these engines - #1 and #6 will be in their correct positions and the engine will not run.
Even though 1-8-4-3-6-5-7-2 seems to be the popular firing order, this does not make it the best firing order. The 4/7 swap was well researched by Comp Cams and found to produce slightly more torque throughout the RPM range than the 1-8-4-3-6-5-7-2 camshafts with a reduction in harmonics.
Does anyone know why Charles Kettering ("The Boss" at GM) would go with the 1-8-4-3-6-5-7-2 firing order on the Cadillac engine in '49 and go with 1-8-7-3-6-5-4-2 firing on the Oldsmobile engine in '49 also. These two engines were hands down the most preferred swap for flatheads and in-line sixes during the fifties because they were plentifull and torquey in stock form.
Also, what was FoMoCo thinking by having two different firing orders for their small block engines?

 

von Dyck, help me out...which two Ford smallblocks? You mean the Y-block and the 260-289, etc. series, which were offered at the same time?

 

Just checked with a Mustang buddy and he says this change is to relieve stress on the respective main bearing. But I dunno. Need another Ford motor guru here. Funny, my buddy referred me to a Mustang 5.0 website. They are puzzling about the same timing order questioin over there, but recommending that you switch the 302 order to the 351 order!!!

Engine voodoo, horsepower folklore and alchemany (turning lead to gold), I suppose.

 

And I would add that the camshaft has something to do with this. While the crankshaft configuration determines piston "position", the camshaft can be ground to change the firing order. For instance, you could have a custom cam ground which changes the traditional SBC firing order from 18436572, to 68731542, or quite a few other variations. As long as the pistons are "Opposite" (1&6, 8&5, 4&7, 3&2) these pairs of cylinders can have their firing orders reversed. Not that there would be any benefit, I just wanted to try to confuse the issue even more

 

Be carefull changing IGNITION firing orders on sbf's. Ignition firing orders MUST agree with camshaft valve opening sequence. Had a student bring his Mustang Fox into the shop with a crappy running 302 (he had bought the car a few weeks earlier) miss-firing on two cylinders. The previous owner had the engine rebuilt using a 351 cam and ran the 302 firing order! Changed to the 351 firing order. Went from gutless to tire shredder with just that one change.
Regarding timing the IHC V8 off #8 cylinder ( or #5 if you so choose), you could do any engine off any sparkplug you choose - using a degree wheel, re-index your harmonic balancer to correspond to the spark plug you wish to time from.
Have you ever tried using a firing order set up this way? Read the chart vertically to see which pairs of pistons run in synch. Handy for setting hydraulic lifters on sbc engines prior to initial fire-up as well as valve lash on solid lifter street cams.
1 8 4 3
6 5 7 2
Example: When #1 is at TDC end of compression, #6 is also at TDC, but at end of exhaust/beginning intake. Rotate crank 1/4 turn, and you'll find #8 at TDC end of compression and #5 at TDC end of exhaust. Just keep rotating 1/4 turns through the firing order. ALWAYS do your valve lash adjustments at TDC end of compression, NEVER at TDC end of exhaust. I learned this from a seasoned engine builder of roller cammed sbc's that ran the modified stock car circuit in southern Ontario and western New York. His engines were consistently in the top five finishers (back in the '60s).
R.I.P. Jimmy Binks

 

The Ford 302 HO has the same firing order as the Ford 351.

 

Boys, I said it once and I'll say it agin...this is the stuff of engine masters, black magic, voodoo, hoodoo and messin' with the horsepower gods. Great stuff here. Graduate school hot rodding.