The V8 is ingrained in American culture. It was the engine that dominated the North American automotive landscape from the 1950s to the end of the 1970s. The V8 has long been a symbol of power, performance and smoothness, but this wasn’t always the case. While V8 engines have been around since the beginning of the 20th century, the earliest iterations used a flat plane crankshaft, making them fundamentally different and rougher running than most of today’s V8s. In the early 1920s, Cadillac and Peerless pioneered the smoother crossplane crankshaft, a design that revolutionized the American V8.
The earliest V8 engines used flat plane crankshafts. This looks like two four cylinder engines that have been joined together at the crankshaft. Like a 4-cylinder engine, there are four crankshaft journals set 180 degrees apart. The front and rear journals are completely opposite in position to the two center journals, forming a flat plane. Also like a 4-cylinder engine, the flat plane V8s are prone to vibration.
In search of a smoother V8, Cadillac and Peerless developed the crossplane crankshaft, first introduced by Cadillac in 1923 and Peerless in 1924. A crossplane crankshaft has the front and rear crankshaft journals oriented in opposite positions, 180 degrees apart. The two inside crankshaft journals are also 180 degrees apart. The front and rear journals are set at 90 degrees to the two center journals. So the crankshaft has journals every 90 degrees, forming a cross shape from the front.
The crossplane V8 is significantly smoother than a flat plane V8 engine and it gave the V8 its reputation for smoothness. The crankshaft geometry eliminated vibrations of the second order. This crankshaft design also gave the crossplane V8 its distinctive exhaust note as it required a unique firing order compared to a flat plane V8. The design was adopted by other manufacturers and it was used by the majority of V8 engines. Some manufacturers, in particular European high performance makes like Ferrari, continued to use flat plane crankshafts, for they offer some advantages in high RPM engines.
Vibrations of the first order are caused by the inertia force produced by the piston mass as it moves up and down in the cylinder. The maximum force occurs when the piston is at top dead center or bottom dead center. A flat plane crankshaft doesn’t have vibrations of the first order, as there is always a counter force from another piston which results in a net force of zero. As the one piston reaches top dead center, this force is countered by piston immediately adjacent reaching bottom dead center. Each of the eight pistons are paired up with an opposite, resulting in no vibration of the first order.
The journals at each end of the crossplane crankshaft do not move together, which causes vibrations in the first order. As the first crank journal travels down from the top of the cylinder, so does the second crank journal, but the third journal is travelling up from the bottom along with the fourth journal. So, one end of the crankshaft has net force upwards, and the other a net force downwards. This creates a force that attempts to rotate one end of the crankshaft around the center of the engine, much like sitting on one end of an unoccupied seesaw. Of course, when the crankshaft rotated 180 degrees these forces reverse. So as the crankshaft rotates it generates seesaw effect, vibrating each end of the crankshaft up and down. These forces can easily be countered. By using heavy counterweights on the crankshaft that oppose the pistons inertia force as they move up and down, the net force will be zero. This eliminates the vibrations of the first order. The downside to the heavier counterweights is that it causes more rotation inertia compared to a flat plane crankshaft, making a flat plane more advantageous in high RPM engines.
A flat plane V8, however, has vibrations of the second order. The piston rod geometry dictates that a piston will travel at a higher velocity when on the top half of its travel compared to the lower half. When a crankshaft journal is at 90 degrees or 270 degrees from top-dead-center, the piston is actually below the halfway point in the cylinder. This means that the piston travels at a higher velocity on the top half of its travel than it does on the lower half as it covers more distance over the same time. As the piston accelerates to the higher velocity, this creates more force (remember F= ma). Due to the piston locations on a flat plane V8 crankshaft, the net velocity of the pistons is not zero. Just like a 4-cylinder, this difference in piston velocity causes vibrations of the second order, non-sinusoidal vibrations, as it spins.
A crossplane crankshaft does not have any vibrations of the second order, as the net velocity of all the pistons is always zero. For each piston movement, there is always a corresponding piston movement that is in the opposite direction at the same velocity, counteracting the forces each creates. With 90 degrees between each crankshaft journal on the crossplane V8 and it being a 4-cycle engine, each cylinder should fire once over 720 degrees of crankshaft rotation. If we divide 720 degrees by 8 cylinders, it means every 90 degrees a cylinder should fire. However, the crossplane crankshaft layout limits the order in which the cylinders can be fired.
Before firing orders are discussed, there is one caveat; not all manufacturers use the same cylinder numbering convention. Ford, in particular uses, its own convention. Most V8s number the left front cylinder as number 1 cylinder with the left bank the odd numbers, 1-3-5-7 and the right bank the even numbers 2-4-6-8. Ford V8 engines have the right bank slightly forward of the left bank, so the front right cylinder is labeled as number 1. However, unlike the other manufacturers, Ford labels the right bank 1-2-3-4 and left bank 5-6-7-8. Some other manufacturers also label the right front as cylinder number one, but unlike Ford, most often the right bank is numbered as 1-3-5-7 and the left bank as 2-4-6-8.
Nevertheless, to compare firing orders, the cylinder numbering must be standardized. For simplicity sake I will use the conventional cylinder numbering, with left bank 1-3-5-7 and right bank 2-4-6-8. In the chart below, I also listed the equivalent firing orders using other numbering conventions. As seen below, there are only eight possible firing orders. Of these, only the first three are commonly used.
Due to the layout of the crossplane crankshaft there will always be an instance when at least two cylinders on each cylinder bank are fired sequentially over 720 degrees of crankshaft rotation. This is what causes that distinctive V8 sound we all know. Two high pressure exhaust pulses are being forced into the exhaust manifold in succession causing a change in tone. In comparison, a flat plane crank will fire evenly between each cylinder bank, left-right-left-right-left -right-left-right, which creates its own distinctive sound and better exhaust scavenging.
Listen to the difference in sound for a GM LS V8 engine with a flat plane vs crossplane crankshaft.
The bottom four firing orders are unique, as they are bank to bank firing orders. This is where all cylinders in one bank fire, followed by all cylinders in the next bank. These firing orders are not used, although some racers have experimented with them and found no advantages. They result in more vibration and a different sound from the others.
The first firing order is by far the most common on traditional American V8s. Most GM, Mopar, Ford and AMC V8s used this firing order. The second firing order was commonly used on many of the early V8 engines, including the Ford Y-block, Olds V8, and Buick Nailhead. In the late 1960s Ford adopted the third firing order on the 351W and the 335 series engines. This firing order wasn’t something new though, as was used by Cadillac on its 429 and its second generation V8 engines. GM also used the third firing order for the LS series engines.
The top four firing orders listed each have one cylinder bank where two adjacent cylinders fire in sequence. The other cylinder bank has two cylinders fire in sequence, but they are not adjacent to one another. Changing between these four firing orders, changes which of the two adjacent cylinders on each bank are fired sequentially. So for the first firing order, which is the most common for V8 engines, the number 5 and 7 cylinders (or the 7 and 8 cylinders on a Ford) fire sequentially. These two cylinders are at the back of the engine block. Both Ford and GM later switched to the 3rd firing order, where the number 3 and 1 cylinder (6 and 5 on a Ford) are fired sequentially which is at the front left corner of the engine.
By moving the location of the two sequentially fired adjacent cylinders, this can have effects on the cooling of the engine, the induction, and the crankshaft harmonics. Firing two cylinders side by side causes extra stress on the crankshaft journals and main bearings, extra heat, and both cylinders may fight for fuel and air. GM switched to the third firing order for the LS engines as it provided better cooling by having the sequentially fired cylinders at the front near the water pump where the engine is generally cooler. It also resulted in better crankshaft harmonics and it improved main bearing durability/wear. Induction issues can result from two cylinders firing side by side, as both cylinders are fighting for the same air/fuel mixture in that same area of the manifold. However, these are can be resolved by intake manifold design.
Engine builders have also experimented with these firing orders on existing engines, in particular on the Chevrolet small-block. A camshaft swap is required, as it controls the cylinder firing sequence. Obviously this requires a custom ground camshaft, although some are available off the shelf for popular engines like the Chevrolet small-block. These swaps are called the 4/7 swap for the second firing order or the 4/7 2/3 swap for the third firing order. The 4/7 2/3 swap can result in slightly more horsepower due to the better crankshaft harmonics, but only in extreme high horsepower/high RPM builds, so it’s not really advantageous unless you need every last horsepower in a racing type venue.
After reading this article, I hope you understand that the crossplane and flat plane crankshafts have a significant effect on how smooth an engine is, how it sounds and its ability to rev. We also learned that the crossplane crankshaft is limited to eight firing orders, of which only three are commonly used. These firing orders always have two cylinders on each cylinder bank that fire sequentially for every 720 degrees of crankshaft rotation. By changing firing orders, one can move which two cylinders fire sequentially, which may have some advantages for a given engine design. And it’s that sequentially firing of two cylinders on the same bank that creates the distinct V8 sound.
Nice job, Vince! This is why I’ve always liked the sound of Ford Y-Blocks; their firing order is a bit unusual. Perhaps it’s also one reason why I can always identify a five-liter Mustang from a block away, although by that line of reasoning I should be able to identify an LS-powered car, as well.
This is tremendous! Even the less mechanically inclined reader should be able to easily follow along.
Years ago when my parents owned their 302 powered Crown Victoria I remember seeing somewhere how the firing order between that lo-po 302 was different from the 302 HO used in the current Mustangs. This definitely gives better insight.
Vince, this is the type of article I like – technical but highly readable. You’ve made my morning.
+1. Great morning read, Vince!
“firing order between that lo-po 302 was different from the 302 HO ”
I remember finding this out myself. One more area where Ford made performance mods harder than Chevrolet did.
It most certainly does not make performance mods harder. Camshafts interchange between the 289/302 and the 351W; therefore either engines can have either firing order just by swapping cams and moving the wires around on the distributor cap.It is a non-issue.
Excellent read, thank you VinceC.
A wrench in the works of standardization was Pontiac with their fake firing order. Cylinder #1, usually the furthest forward cylinder, was called out as #2 by Pontiac.
Far out, thanks Vince. The big Cadillacs always did have their own sound.
Fords drive me nuts. While GM and Mopar almost always use 1-8-4-3-6-5-7-2, they just had to be different. The firing orders are even different across engine families.
Thanks for explaining the flat plane crank too. Inever really grasped what they were before but now I do.
Being a Ford guy their order is indelibly etched into my memory. So just guess what happened when I changed out the timing gear set an my, new to me, Dodge 360. Going by long term memory/habit and I couldn’t figure out why my timing light was way off when hooked to #1.
We’re talking about a company that had three different 351 c.i. V8s in the same timeframe 😉
Right, as opposed to a company that was building a 351 and also four unique 350 engines?
Man, you do have a skill for teaching. Superb.
I don’t 100% follow the second order vibration cause (amuse yourselves, CCers, with the image of a middle-aged man doing an air dance with hands and fists to try visualize it, much to eye-rolling of the kid present who’s having it confirmed again that I’m a nut). If 180 degrees is full stroke from TDC, how is the piston more than half-way down at 90 or 270? And why then faster going up?
On sounds, flat-plane V8’s sound boring to me, like some hi-po 4cylcinder, and in fact, if blindfolded, I’d be hard-picked to tell.
For your interest, the local Holden V8’s used the “”older” second order of firing (12784563). They have a distinctly harsher sound. They’re sometimes called the “thong slapper” (“thong” in Aus being rubber flip-flops and not skimpy knickers), which is about right for the sound. These V8’s incidentally, were designed by a former V1-rocket engineer and Luftwaffe pilot who came here as a refugee in the late ’40’s. Being the parochial Oz of the time, his qualifications weren’t recognised, but someone at Holden quickly worked out what this “draftsman” fellow could do, and made him project engineer. And being Oz of the time, the lack of qualifications was quietly ignored!
Great stuff, Vince.
“If 180 degrees is full stroke from TDC, how is the piston more than half-way down at 90 or 270? And why then faster going up?”
The piston is connected to the rod, which it connected to the crankshaft. Piston goes up and down, crank journal spins in a circle. Connecting rod does both, depending on where you measure the motion.
From TDC to 90 degrees, the bottom end of the rod is going down, but also away from cylinder center-line. Piston travels the full half-stroke PLUS the additional distance away from cylinder center. It has to travel farther than from 90 to 180 degrees, where the bottom of the rod is going down, but returning to cylinder center-line–1/2 stroke MINUS the distance back to cylinder center-line
The upstroke is reversed. From 180 to 270, the bottom of the rod is going up, but also away from cylinder center-line. It travels farther than from 270 to 360/0 where it’s still going up, but also returning to center.
Brilliant, thankyou, Shurkey.
(I’m quietly pleased that I was closer than I thought, but I’d decided my hand movements in the air were somehow stretching the imaginary rod improbably!)
Actually, the rods do stretch and that’s not insignificant. Even if they are well within the elastic zone, thus no risk of rod failure, it can affect piston to valve clearance. And especially in a pushrod engine with rockers, where flex of the valve train components can affect true valve timing, and thus the actual proximity of valve to piston at any given point (as well as affecting performance of course). Interestingly, this is one of the few things directly related to engine design I actually learned in college, in an otherwise difficult dynamics class. Our very academic, seemingly not hands-on professor had done some consulting on this phenomenon for an aftermarket performance camshaft company (he didn’t share the name)., and discussed it in one class. This was in the mid-70’s when performance was still spelled V8. FYI, the geometric motion of these parts is an example of the discipline known as kinematics; throw in the forces and loads caused by acceleration and mass, and it becomes what is known as dynamics.
and it’s this non-sinusoidal motion that generates the harmonic (2nd- and 3rd-order energy.)
same phenomenon which causes harmonic distortion in audio equipment (amplifiers and speakers.) any non-sinusoidal energy contains harmonics. Inline 4 cylinders (and flat-plane V8s) are bad because the pistons all reaching TDC/BDC simultaneously and reversing direction means that harmonic energy sums together. Only easy way to cancel it is with Lanchester balance shafts.
Since a crossplane V8’s pistons don’t move in lockstep, the harmonics don’t sum.
Thank you Justy for you kind word and the information on the Holden V8s. This attached diagram may help you better visualize and understand piston rod geometry. It includes measurements to show the piston’s position for a 4″ stroke.
I kinda like that stacatto Holden V8 sound, even the little 253 sounded mean especially when the mufflers fell off.
Dang ole 350 man That son gun run fo ever man. Need to bring them back !! The ole sayin ain’t broke sell your tools.
The Holden V8 also had the right-hand bank forward (presumably to make a slight difference for a RHD steering column) and cylinder no. 1 was on the right hand side.
Yes Holden V8s have a real stacatto sound, especially thru headers to open pipes
Good stuff, thanks!
I don’t think you mentioned the current Ford flat plane V8 used in the Mustang Shelby GT350. Reviews have raved about the engine’s power and particularly its sound. I haven’t heard one in person, but the videos I’ve seen I just can’t warm to its sound. Maybe it’s because I like the regular Mustang GT’s exhaust note so much. The conventional American V8 exhaust is my favorite exhaust by far, which I think is the reason I have never found the Ferrari V8 engine sound very satisfying. They sound more like four cylinders to me.
You’re article helped me understand the concept of the flat plane much better, thanks!
No, I didn’t really mention Ford’s 5.2L flat plane V8. I was going to but the crankshaft on the Ford variant is somewhat unique in its orientation (see attached photo). I thought it might be somewhat confusing if I included it. Nevertheless, all that is said for the flat plane still applies to the Ford version too.
While I love the crossplane V8 burble, I also like the flat plane V8 sound too. I had the chance to drive a Ferrari several years ago and the sound was quite intoxicating.
IIRC that crankpin config along with keeping the Coyote’s 4-3-1 headers let them keep some of the crossplane “burble;” the Voodoo doesn’t really sound like a traditional flat-plane at all. You only really notice the difference high in the revs.
+1, and what Jon said Vince… This was exactly what I was going to say.
I also read that the GT350 is going away soon (in a Motor Trend speculative article that popped up in my email) so with it goes away that VooDoo engine with its Flat Plane Crank.
I think the GT500 is going to stick around, and its engine has a Cross Plane Crank.
Now I get the difference! Thanks Vince!
Maybe it’s just me, but the flat-plane V8 sounds more like a cammed engine. In fact, I wonder if the combination of a flat-plane crankshaft and OHC is what, for years, contributed to the Ferrari engine’s unique, high-rpm ‘ripping-canvas’ shriek.
The location of a camshaft has no bearing on the sound of the engine. That’s the whole gist of this article. It’s the type of crankshaft and firing order that determines the sound.
Number of valves absolutely makes a noticeable difference, which is facilitated by OHC. All those modular variants used in Mustangs 2V, 3V, 4V have distinctive notes, yet all share the same firing order. And while there are other factors in being totally different engines with different bore/strokes, there’s an even more notable difference in tone between the 5.0 H.O. and 4.6 2V, despite the same number of valves. Firing order matters, but it’s not the only factor, it’s just another factor to color the sound
I didn’t say “number of valves”, did I? I said “location of the camshaft”, which does not need to be overhead, as the four valve Honda CX500 (and other engines) proved.
And although I’m not in a position to debate the sounds of those engine you listed without having them all on front of us to listen to, I’m skeptical. The 3V and 2V heads both have a single exhaust valve. How would the additional intake valve change its exhaust sound? Makes no sense, unless I’m missing something.
Frankly, I doubt that having two exhaust valves compared to one can be discerned aurally, all other things being equal, which they typically aren’t. I strongly suspect the engines you’re hearing as sounding differently had different exhaust systems and/or other aspects that make them sound different to you.
Listen to a 4.6 SOHC SN95 with the common Flowmaster 40s and a 5.0 Foxbody with Flowmaster 40s, these are the most common and ubiquitous exhaust system modifications to Mustangs and the pipe layouts are identical. They sound different, in video and in person.
Do I attribute it to the cam position alone? No, but cam position does come with inherent advantages that are worked into other factors that effect sound, such as lift, duration and overlap. If the cams were equal in those measures, they’d probably sound the same, but those measures are specifically tailored to their positions in the engine to achieve their similar respective outputs
The 3V you’re right, as it was on a different chassis with a much different exhaust layout
Exhaust plumbing can change the sound more than camshaft location which wont alter anything if the firing order doesnt change.
Flowmasters sound very different depending on where they are placed in the exhaust system.
They are in the exact same location in Foxes and SN95s other than the tips the systems are identical from manifolds/headers to the bumper
an engine’s “core” sound character is determined by its cylinder layout and firing pattern, period. you can tune and shape the timbre and other characteristics via exhaust tuning, but like using the “tone” knob on a guitar an E chord is still an E chord whether it’s clean or overdriven.
Thats as simplistic as saying a Gibson Les Paul sounds the same as a Fender Stratocaster both tuned to E standard and strumming the same E chord through the same amp. Pitch =/= character.
This really helps explain the difference between flat- and cross-plane crankshafts, which I struggled with until seeing it here. It also explains why you never see a firing order where the cylinder banks fire L-R-L-R-L-R-L-R, which as you said, creates that distinct “burble” that we associate with commonly seen V8s.
By the way, there’s a minor error on the diagram showing the engines from above and their firing orders. As shown, the Ford flathead never fires cylinder number 4, and it fires cylinder number 3 twice in succession!
Excellent explanation of several things that I didn’t quite grasp before this. I very much like the sound of a flat-plane engine, the two video sound clips were great. Thank you.
Some of the newer Yamaha inline four cylinder engines used on high performance motorcycles use crossplane cranks. With essentially unmuffled racing exhausts the sound is very distinctive in a herd of otherwise flatplane Suzuki, Kawasaki, Honda and BMW fours.
I am not a motorcycle guy but I was aware of the crossplane 4-cylinder Yamaha engine. It’s a neat idea, but I have never heard on run. It looks like a crossplane V8 cut in half, since it bascially is one.
it is. Apparently in racing situations having an “unbalanced” firing interval gives the rider better control when trying to modulate power through a corner.
http://www.youtube.com/watch?v=6is0wxF7HFk
I regularly get the itch to trade my FZ-09 up to an MT-10 which has the same crossplane 4 banger.
Awesome lesson, thank you very much. And now for the crazy world of the V6. Buzzdog, the GM 305 V6 fires alternating banks 1-6-5-4-3-2. With dual exhaust and blown out glasspacks you can easily identify which bank is firing at a slow idle. Guaranteed to set off every car alarm in the parking lot.
Thanks Vince! This is a superb addition to our growing tech section. You’ve explained it more clearly and concisely than I’ve ever read before.
Completely fascinating — most of this is stuff I’ve never thought of. And how many times I’ve admired the sound of a V8, I never stopped to wonder just where that sound was coming from.
VinceC, with the coffee half down I believe that there may be an error in the firing order-to-cylinder numbering chart.
If the chart’s column #1 “Conventional Cylinder Numbering” would be with 1357 on the left or “Chevrolet” numbering, that clicks.
Column #2, Ford, also computes.
However, column #3 seems like it could be called “Mirror Chevrolet” and probably should read: 1357 Right 2468 Left.
I think…
Maybe after the rest of the coffee I’ll change my mind.
Thank you, that was a typo in my chart – it’s fixed now. It should be right 1-3-5-7 and left 2-4-6-8.
Great article but the graphics for the Ford flathead and Coyote firing orders are incorrect. They show #3 cylinder firing twice and nothing for #4.
Thanks, I see this is the second time that error was pointed out. That picture of the firing orders isn’t something I created. I obviously missed the firing order on the flathead/Coyote as well as the Nailhead numbering. I have since edited the image and fixed it.
Thank you for all the great feedback from all. And thanks to Daniel Stern for inspiring this article.
Glad to inspire—thanks for such an outstandingly comprehensive and educational article!
Is there a similar science to the V6 firing order? I’ve always wondered why the prior generation Chrysler V6’s (the 3.5 in particular) had such a smooth, husky sound while everyone else’s sounds like a pump motor.
Yeah, eh! It seems like everyone’s very recently figured out how to make V6s that don’t have an ugly, crude, blatting sound to them. I noticed a nice sound from the V6 in a ’15(ish) Mustang I rented some years back and a V6 Transit I rented earlier this year, and in a couple of 3.6-litre Chrysler Pentastar motors, and in something otherwise forgettable from GM recently.
the big difference is whether it’s a 90 degree V6 with split crankpins, or a 60 degree V6 with a “flying pin” crankshaft.
Yes, it’s a whole other topic for V6’s. But like jz78817 mentions, the biggest difference in the common V6’s has to do with the V angle (90 vs 60). The earliest 90 degree engines did not have split pins as a result were “odd fire” engines. The newer split pins allowed an even fire.
Great read! Firing order was one of the things that took me a while to understand the importance of, and few experts and educators made much of an explanation I found satisfactory. I wish I found something as well written 10 years ago when I was a novice car guy who proudly memorized the common orders, but couldn’t explain why they were different!
I’m a visual self learner, and ended up drawing the patterns on paper myself to examine, making note of their locations on the engine, it made more sense their purposes, with cooling and crank harmonics taken into account. The first pattern adds heat to the back corner, which is a spot that inherently suffers in typical cooling system designs as is, and also fires sequentially on the pins towards the front of the crank with only the light damper to “cushion” the harmonics, which could lead to a broken crank in high performance applications. The second firing order is a perfect mirror image of the first order in its pattern, but places moves the hotspot to the front corner and flips the load on the back of the crank, damped by the heavy flywheel end – I still don’t understand why these two sound different as they do though, given the pattern being identical – The 4/7 order is like a mix of the two, and moving the front sequentially fired cylinder pairs to the opposite and typically coolest running corner.
I drew this pattern sheet a while back for a forum discussion I was part of
Nice work.
Regarding firing orders, Ford and the 302/351W firing variation messed me up once back in the day since the camshafts physically interchange. I was installing a rebuilt engine for a customer and because the cap and wires were relatively new and in good condition I swapped them over as-is in one piece. Well time came to fire it up and the engine that wasn’t too happy, spitting back through the carb. Now these wires were nicely arranged in (aftermarket) holders so I was pretty sure I installed them exactly as them came off. However when I did check the firing order the wires didn’t match the proper order for a 351W they were for a 302. When I inquired with the customer he did finally come clean that the old engine “had a cam” and obviously it was ground with the 302 firing order. Swapped the wire around and if fired up and ran properly.
The one engine I don’t see mentioned is one of my favorites, the IH SV (Small Vee). It uses that 1-8-4-3-6-5-7-2 but for what ever reason, as noted on the valve cover you time V-8 on cyl #8. What? Why do the valve covers on a V-8 say to time V-8s on #8? Well because they also cut off a bank and made a 4cyl version and it used the same valve cover. It was timed on the conventionally used #1 cylinder, and of course doesn’t have a cyl #8.
The other aspect of the paired firing is the potential for potentially damaging inductive cross firing. When #5 is firing in that common order, #7 is finishing its intake stroke and has no/negative pressure. That means it won’t take much voltage for a spark to jump the gap and having that #5 and #7 running parallel for their entire distance can induce enough voltage for a spark to occur in #7.
So on that SV, the proper set of plug wires has 3 with straight boots and 5 with 90 degree boots, one of them really long. The 3 straights are supposed to go up and over the water outlet to 1-3-5 while the 90 degree ones are supposed to point to the even bank for 2-4-6-8 and 7 & goes along with 8 and then across the back of the intake before it gets to the spark plug.
The funny thing is Chrysler engineers apparently had forgot about that by the 90’s and the fact that higher spark voltages make it worse. http://dodgeram.info/tsb/1998/18-48-98/18-48-98-v8.htm Note D & E
Right on the money. I remember my first couple Automotve instructors emphasizing plug wire routing to minimize the potential for cross-fire. ” Watch #5 and #7″ they’d say.
Fascinating detail! Love reading these deep dives…
This is interesting stuff, Vince. I remember it was always frustrating in the pre-internet days to figure out which was the number 1 cylinder on a V8 for hooking up the timing light. I guess having too many Fords among my circle of friends complicated things.
Which of course is why the Chilton’s, Clymers, or Haynes manual was so important back in the day. Either the vehicle specific or the big book that covered all US or all Imported models for a range of years.
Or rather books that SHOULD have been helpful.
Without covering an old long boring headscratcher of a Nailhead Buick story that has to do with a mistake printed in the manual, I can see in this very thread that some 50 years on the wrong cylinder numbering is still being published for Nailhead.
The correct Buick numbering is PS 1357, DS 2468. The posted firing order chart has the cylinder numbering mirrored.
Well apparently I shouldn’t have trusted a chart made by a major ignition company without checking it more closely. It had several errors, not only the cylinder numbering on the Nailhead wrong (it did have the correct firing order though), the flathead was wrong and the distributor on the Y-block and the Nailhead was on the wrong end. I edited the photo and checked it over more closely now and it looks good.
Enough of the easy stuff, Vince – let’s move onto V-16s. 🙂
Yeah, then we get to talk about different V angles too. Cadillac had two different V-angles for its two V-16s, one at 45 degrees and the other at 135 degrees.
Narrow angle v6 and v12 motors is where its at, man
I’m really intrigued about straight 8s too, which were long before my time and I’ve never driven one, but I know they’re renowned for being very smooth with primary and secondary balance etc., but that stresses on that long crankshaft are problematic (or something like that) and thus they were usually less powerful than V8s. The length of the engine was held against it too, but I didn’t see hoods being shortened after I-8s were phased out by 1955. I’m left wondering if another 65 years of development may have solved most of their issues and we’d have some buttery-smooth straight-8s today. Isn’t smoothness and low NVH what drives many buyers to look for V8 (or even V6) engines in an era when turbo 4s can produce 300+ hp?
Excellent article Vince, well written and easy to follow. Something I have often wondered about. Thank you for doing that
Don’t forget Yamaha went with a Crossplane Inline 4 back in 2008 or so in their R1. It spread out power pulses to provide the rear tire to recover traction. Nice site explaining it.
https://www.yamahapart.com/crossplanecrankshaft
Made for a different sound on race tracks. Very cool to hear.
The firing order may also be why the air cooled Volkswagen sounds so unique. The firing order is 1-3-4-2, which means 3, then 4 fires on the left side, then 2, followed by 1 on the right. Seeing as how I’ve learned from this article that stresses and vibrations are higher when sequential pistons fire on the same bank, I wonder why VW didn’t do it differently say 1-3-2-4, not to mention why they wanted intake gases going down the same long intake tube to the single-port intake for both cylinders which ate them one after the other.
How does Subaru do it with a flat four? They sound very much like my old VW’s.
The firing on a boxer 4-cylinder is due to the crankshaft layout. See the diagram below (click to see animation). This crankshaft layout results in a an engine that has balance in the first and second order, and the firing order creates that unique exhaust note that Subaru owners are very familiar with.
I think there may be an advantage to firing both cylinders on the same side sequentially. Air has inertia just like any fluid. The first cylinder gets the column of air moving down the shared intake, then the second can get a little “supercharging” effect since the air is already moving in its direction. Similar to how the tuned, variables intake manifolds in common use today work.
The reason sequential firing is bad for old SBC’s but good for old VW’s is just a matter of intake manifold design.
it depends what your goals are. if you’re building a circle track race engine, then maybe; you’d use a high-flow single plane intake in that case. but that kills your low end power, idle quality, and manifold vacuum (gets worse depending on how much overlap your cam is ground for.) Street-oriented V8s almost always have had dual-plane intakes, and the key thing a dual plane intake does is make sure cylinders firing sequentially are pulling from separate intake planes.
Great write up, Vince, but you forgot to list the firing orders for counter-rotating marine engines. 🙂
Usually, start with #1 and follow the order backwards.
Absolutely terrific article, one of the best here, and that is high praise indeed. To stand out amongst the creme de la creme is an achievement. Best explanation I’ve ever read, which includes those in several technical books
Any thoughts on the production 65 degree Dino V6? Each piston uses a single crankpin that is offset by 5 degrees to compensate for the block V while maintaining 60 degree ignition interval with a 1-4-2-5-3-6 firing order where the RH head is 123 and the LH 456.
Also what crank distinctions may apply to narrow angle V engines like the Lancia V4 series or the VW VR6?
The most fantastic explanation of the unique V-8 sound, which I, being more of a layman, wondered why it always had that one louder pop when there was always 90 degrees between firing. Thank you so much!
Yes, fantastic explanation of the sound of a crossplane V8 – marvelous.
Outstanding job, Vince! Somehow I missed this article when it first ran, but I’m pleased I caught it this time around.
You explained things clearly, yet in great detail. You also answered several questions of mine, two of which were:
Why did Chevy change their firing order?
What’s the big deal with flat plane cranks?
While these questions didn’t exactly keep me up at night, I’m now a more complete man. ….and I still prefer the split plane burble.
Again, my thanks for such a fine write-up.
Yes Holden V8s have a real staccato sound, especially thru headers to open pipes