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By Engine Simulator Team17 min read

Firing Order Explained: SBC, LS, Ford, Hemi and Diesel Orders

Firing order is the sequence an engine's cylinders fire in: the SBC, LS, Ford, Hemi, Duramax and Power Stroke orders, cylinder numbering, and what it changes.

A V8 engine seen from above, distributor at the front, with two spark plug wires glowing as they run to cylinders on opposite banks

Every multi-cylinder engine fires its cylinders in a fixed sequence, and that sequence is its firing order. A small-block Chevy fires 1-8-4-3-6-5-7-2. A GM LS fires 1-8-7-2-6-5-4-3. A Fox-body 5.0 HO Mustang fires 1-3-7-2-6-5-4-8, a Coyote Mustang 1-5-4-8-6-3-7-2, and an older 302 1-5-4-2-6-3-7-8. You need the number whenever you wire a distributor, replace coil packs or swap a camshaft, and you need to know how that engine's maker numbers its cylinders before the number means anything.

This article has the common orders in one table with their sources, explains the numbering, and then answers the question the forums argue about: does firing order change power or sound? We tested it in our simulator by typing four different firing orders into the same V8. You can open that V8 with the LS order and hear it.

Key Takeaways

  • Firing order is the sequence in which the cylinders of an engine fire. It is set by the crankshaft and camshaft (and, on older engines, the distributor), and the spark plug wires or coils must follow it.
  • Common V8 orders: small-block and big-block Chevy, older Chrysler and Gen III Hemi 1-8-4-3-6-5-7-2; GM LS and LT 1-8-7-2-6-5-4-3; Ford 289/302 1-5-4-2-6-3-7-8; Ford 5.0 HO, 351W and 4.6/5.4 modular 1-3-7-2-6-5-4-8; Ford Coyote in the Mustang 1-5-4-8-6-3-7-2.
  • The same digits mean different cylinders on different makes. GM and Chrysler gasoline V8s put odd cylinders (1-3-5-7) on the driver side; Ford numbers 1-2-3-4 down the passenger side and 5-6-7-8 down the driver side.
  • In our simulator, changing a V8's firing order while keeping the 90° spacing changed its power by nothing at all: 297.251 hp for all four orders tested. It did change the rhythm of exhaust pulses down each bank, which the simulator routes to each bank's exhaust sound. The real reasons engineers choose an order (crankshaft vibration, bearing loads, cooling, intake distribution, exhaust pulse interaction) are effects this model does not simulate, so its zero is the order with those effects taken out.
  • In the simulator, the spacing between firings changes more than the order does. On its V-twin, bunching the two firings from 360° apart to 180° apart raised the crank-speed ripple at idle by 54%.

On this page: Quick answer · Firing order table · Cylinder numbering · Small-block Chevy · LS and the 4/7 swap · Ford 302 vs 5.0 HO · Does it change power or sound? · Why engineers choose an order · Uneven firing · Try it · FAQ · How these numbers were made

Quick Answer: What Is a Firing Order

A firing order is the sequence in which an engine's cylinders reach their power stroke, written as cylinder numbers. In a four-stroke engine every cylinder fires once per two crankshaft turns, 720°, so an eight-cylinder engine fires one cylinder every 90° of crank rotation and a six every 120°. The order says which cylinder takes each of those slots.

The crankshaft's throw positions and the camshaft's lobe timing fix the order when the engine is built. You cannot change it by moving plug wires: wiring the plugs out of order sends the spark to cylinders that are not ready for it, and the engine runs badly or not at all. Changing a firing order for real means a camshaft ground for the new order, plug wires or coil wiring to match, and on an engine with electronic control, a matching calibration. A V8's crankshaft allows more than one order, so the crank itself can usually stay.

Firing Orders for Common Engines

EngineFiring orderCylinder numberingSource
Chevrolet small-block (Gen 1 and 2) and big-block (except 8.1 Vortec)1-8-4-3-6-5-7-2odd on driver sideSummit Racing
GM LS (Gen III and IV), LT (Gen V) and 8.1 Vortec1-8-7-2-6-5-4-3odd on driver sideSummit Racing
Chrysler Gen III Hemi (5.7, 6.1, 6.4)1-8-4-3-6-5-7-2odd on driver sideSummit Racing
Ford 289 and 302 (non-HO)1-5-4-2-6-3-7-81-4 passenger side*OnAllCylinders
Ford 5.0 HO and 351 Windsor1-3-7-2-6-5-4-81-4 passenger sideSummit Racing
Ford 4.6 and 5.4 modular1-3-7-2-6-5-4-81-4 passenger side*OnAllCylinders
Ford 5.0 Coyote (Mustang, 2011-2014 F-150)1-5-4-8-6-3-7-21-4 passenger sideSummit Racing
Ford 5.0 Coyote (2015 and later F-150)1-3-7-2-6-5-4-81-4 passenger sideSummit Racing
Ford 6.7 Power Stroke diesel1-3-7-2-6-5-4-81-4 passenger sideDieselHub
Ford 7.3 Power Stroke diesel1-2-7-3-4-5-6-8odd on passenger sideDieselHub
GM 6.6 Duramax diesel1-2-7-8-4-5-6-3see noteDieselHub
Dodge Viper V101-10-9-4-3-6-5-8-7-2not given by sourceMaxxECU wiring guide
Most inline-fours1-3-4-2 (some 1-2-4-3)front to backWikipedia
Most inline-sixes1-5-3-6-2-4front to backWikipedia

* Ford's passenger-side 1-4 numbering is given on Summit Racing's 351 Windsor and Coyote pages and on DieselHub's 6.7 Power Stroke page; the pages cited for the 289/302 and modular orders give the order only.

Older Chrysler small blocks, AMC, Buick, Oldsmobile and Pontiac V8s also use 1-8-4-3-6-5-7-2, according to OnAllCylinders' firing order guide, though their distributors turn in different directions. The Duramax note: sources disagree on which bank carries the odd cylinders, so check the cylinder numbers cast or printed on the engine itself before you rely on the order.

How Cylinders Are Numbered

A firing order is only useful if you know which cylinder is "3". Makers number V8s two different ways, and the same string of digits means different cylinders on each.

GM and Chrysler number along the crankshaft, alternating banks: cylinder 1 is at the front of the driver side, 2 at the front of the passenger side, 3 behind 1, and so on, so the driver bank holds 1-3-5-7 and the passenger bank 2-4-6-8. Summit Racing's pages for the small-block Chevy, the LS and the Gen III Hemi all give this layout.

Ford numbers one bank and then the other: 1-2-3-4 front to back on the passenger side, 5-6-7-8 on the driver side, as on the 351 Windsor and the Coyote. The Wikipedia firing order article notes that Audi and Porsche number their V8s by bank too.

Diesels do not always follow their brand. The 7.3 Power Stroke was a Navistar design and puts the odd cylinders on the passenger side, according to DieselHub, while the later 6.7 Power Stroke uses Ford's 1-4 passenger-side layout. Before wiring anything on an engine you have not worked on before, find cylinder 1 on that engine.

Small-Block Chevy Firing Order: 1-8-4-3-6-5-7-2

The small-block Chevy, from the 265 through the 350 and 400, fires 1-8-4-3-6-5-7-2, with cylinder 1 at the front of the driver side and the distributor turning clockwise. The big-block 396, 427, 454 and 502 use the same order; the later 8.1 L Vortec big-block switched to the LS order, according to Summit Racing. Enough people type it as one number that "18436572" is a search term in its own right.

Read against the GM numbering, the order alternates mostly between banks: 1 (driver), 8 (passenger), 4 (passenger), 3 (driver), 6 (passenger), 5 (driver), 7 (driver), 2 (passenger). Two pairs fire back to back on the same bank, 8 then 4 on the passenger side and 5 then 7 on the driver side. That is a property of every cross-plane V8 and it is where the V8 burble comes from, as the section on uneven firing explains.

LS Firing Order and the 4/7 Swap

GM's LS engines changed the order to 1-8-7-2-6-5-4-3. It is the small-block order with cylinders 4 and 7 swapped, and 2 and 3 swapped. Hot rodders fit small-blocks with camshafts that make only the first of those swaps, 1-8-7-3-6-5-4-2, and call it the "4/7 swap".

GM's reason was the crankshaft. According to OnAllCylinders, reduced crankshaft torsional vibration was "the main reason GM adopted" the LS order, and the change also eased bearing loads and made the crank position sensor's reluctor wheel read more accurately. EngineLabs gives the same torsional-vibration reason, plus a cooling one from Comp Cams' Billy Godbold: the swap moves the pair of cylinders that fire back to back toward the front of the engine, near the water pump.

On power, the camshaft makers are cautious. Godbold told EngineLabs that "most of the smart guys will tell that there might be one percent difference if you get everything right." OnAllCylinders reports that gains of one or two percent are common and puts part of that down to cooler-running rear cylinders.

We put both orders into the simulator's 5.0 V8 and ran both on the dyno: 297.251 hp at 7,000 rpm and 445.157 N·m at 3,841 rpm for each, identical to the third decimal place, with identical idle. That zero comes from what the model leaves out. It treats the crankshaft as rigid and does not model torsional vibration, bearing loads, cylinder-to-cylinder cooling, how a plenum shares mixture between runners, or how exhaust pulses from neighbouring cylinders interact in the manifold. What it isolates is the order itself: with the same 90° spacing and none of those effects, the order moves no power. Whatever a real 4/7 swap gains, around 1% by the cam makers' own figures, comes through those effects.

Ford 302 vs 5.0 HO Firing Order

Ford's small-block V8 has two orders. The 289 and the regular 302 fire 1-5-4-2-6-3-7-8. The 5.0 HO (high output) Mustang engine and the 351 Windsor fire 1-3-7-2-6-5-4-8, and so do the 4.6 and 5.4 modular V8s and the 6.7 Power Stroke diesel. The Coyote 5.0 in the Mustang uses a third order, 1-5-4-8-6-3-7-2.

Ford's stated reason for the HO change is sound. OnAllCylinders reports that Ford's engineers made the switch "to improve the intake manifold sound quality", while noting that forums have argued for years about whether bearing loads were the real motive. A 302 being converted to an HO camshaft, or the reverse, needs its plug wires reordered to match.

Does Firing Order Change Power or Sound?

To answer this directly, we took the simulator's 5.0 L V8, which uses GM numbering and the small-block Chevy order, and typed in three more firing orders: the LS order, an order that alternates banks on every firing, and an order that fires all of one bank before the other. We ran each on the dyno and idled each for 30 seconds.

Four groups of two strips, one strip per cylinder bank, with a mark at each firing over one 720 degree cycle. The small-block Chevy and LS orders both give each bank the uneven 90, 180, 270, 180 degree rhythm of a cross-plane V8, shifted. Alternating banks gives an even 180 degrees on each bank. Firing one bank and then the other gives 90, 90, 90, 450. Measured peak power is 297.251 horsepower for all four.

Firing order on the 5.0 V8Peak powerPeak torqueIdle variationDriver bank (1-3-5-7) intervalsPassenger bank (2-4-6-8) intervals
Small-block Chevy 1-8-4-3-6-5-7-2297.251 hp445.157 N·m0.356%270-180-90-180°90-180-270-180°
LS 1-8-7-2-6-5-4-3297.251 hp445.157 N·m0.356%180-270-180-90°180-90-180-270°
Alternating banks 1-2-3-4-5-6-7-8297.251 hp445.157 N·m0.356%180-180-180-180°180-180-180-180°
One bank, then the other 1-3-5-7-2-4-6-8297.251 hp445.157 N·m0.356%90-90-90-450°90-90-90-450°

Power, torque and idle are the same for every order. With the firings still 90° apart, the crankshaft receives the same eight pushes per cycle, only from different cylinders, and in a model without crank vibration or exhaust pulse interaction that makes no difference to what comes out of the flywheel. We repeated the test on the simulator's inline-four (1-3-4-2 against 1-2-4-3) and inline-six (1-5-3-6-2-4 against 1-2-3-4-5-6) with the same result: 116.39 hp and 193.47 hp, unchanged.

What does change is what each exhaust manifold hears. The small-block and LS orders give each bank the same uneven rhythm, gaps of 90, 180, 270 and 180 degrees, starting at a different point in the cycle. That rhythm is the cross-plane V8's burble. An order that alternates banks gives each bank an even 180°, the rhythm of a flat-plane V8. Firing one bank and then the other gives three quick pulses and a long silence on each side. The simulator routes each bank's pulses to that bank's exhaust in its sound, so in the simulator these four orders sound different while making identical power. A real cross-plane crankshaft cannot fire the alternating order, and it cannot fire 1-3-5-7-2-4-6-8 as written either; the simulator lets you type both, which makes them thought experiments. A real engine given a different order would also change the vibrations the model leaves out.

Why Engineers Choose a Firing Order

If the order does not change power in the model, why does every engine have a particular one? Because of the effects a rigid-crank model ignores. The sources above give these:

  • Crankshaft torsional vibration. Every firing twists the crankshaft slightly. The order decides where along the crank those twists land and how they add up, and GM's LS change was mainly about reducing them.
  • Main bearing loads. Two neighbouring cylinders firing one after the other load the main bearing between them twice in quick succession. Luke Bandt of Howards Cams told EngineLabs that bearing wear "will look a lot nicer" after a 4/7 swap on a high-power engine.
  • Cooling. On the small-block Chevy, cylinders 5 and 7, which fire back to back at the rear of the driver side, tended to run hotter, according to OnAllCylinders. The 4/7 swap moves the back-to-back pair nearer the water pump and its cooler coolant.
  • Intake distribution. "There's always a lot of mixture robbing in a plenum," engine builder Kenny Duttweiler told EngineLabs: the order changes which cylinder draws from the plenum just after its neighbour, and so how evenly they fill.
  • Exhaust pulses. The order sets which cylinders' exhaust pulses meet in each manifold and when, which is also why Ford could describe its 5.0 HO change as a sound change.

On an inline-four the crankshaft leaves only two possible orders, 1-3-4-2 and 1-2-4-3, because cylinders 1 and 4 always move together. On a V8 the crank allows several, and the camshaft picks one.

Even and Uneven Firing: V-Twins, Crossplane Bikes and the V8 Burble

In the simulator, the spacing between firings changes more than their order does. An engine with evenly spaced firings gets an evenly spaced series of pushes on the crankshaft. Bunch them together and the crank speeds up and slows down more within each cycle.

Harley-Davidson's 45° V-twin is the famous uneven engine. Both connecting rods share one crankpin, so, as Jalopnik explains, the two pistons fire 315° apart and then wait 405° for the next pair. That spacing is the "potato-potato" sound. We took the simulator's 1,340 cc 45° V-twin, which fires 405° and 315° apart like the Harley, and tested four spacings at its 1,000 rpm idle.

Bar chart of crank-speed ripple at idle on one V-twin. Even 360 degree firing gives 25.4 rpm of ripple per cycle, the Harley 405 and 315 degree spacing 28.7, 270 and 450 degrees 32.2, and 180 and 540 degrees 39.1.

Firing spacingCrank-speed ripple at idle (peak to peak per cycle)Peak power
360° / 360° (even)25.4 rpm58.88 hp
405° / 315° (Harley 45°, stock)28.7 rpm58.93 hp
270° / 450°32.2 rpm58.92 hp
180° / 540°39.1 rpm58.95 hp

Peak power barely moves: 58.88 to 58.95 hp, a spread of 0.12%. The crank speed swings 54% more within each cycle when the two firings are 180° apart instead of 360°. That is torsional unevenness at the crankshaft; the shaking a rider feels on a real V-twin also comes from the reciprocating imbalance of the pistons, which this model does not compute. The Harley's own 405/315 spacing sits close to even, 13% above it.

Yamaha went the other way on purpose. The 2009 YZF-R1, the first production motorcycle with a crossplane crankshaft, fires its four cylinders at "an uneven firing interval of 270-180-90-180 degrees". Yamaha explains that the crank layout cancels the inertial torque of the pistons, so that what reaches the rear tyre is "torque that is produced purely from the combustion force", which riders feel as better traction out of corners.

The cross-plane V8 is uneven too, but per bank rather than overall. The engine as a whole fires every 90°, smoothly. Each bank of four, though, fires at gaps of 180, 90, 180 and 270 degrees, as the Wikipedia crossplane article puts it, and when each bank's exhausts merge into one pipe that uneven rhythm becomes the burble. Our article on cross-plane vs flat-plane V8s measures the difference that makes to the sound.

Try It in the Simulator

Open the 5.0 V8 with its small-block Chevy order and start it. The firing order sits in the spec panel as a text field; type a new order, press enter, and the engine fires in that order immediately. Rev it and listen, then type the LS order and compare. Then try the alternating-bank order, which gives each bank the even rhythm of a flat-plane V8. Run the dyno on each and the peak figures come out identical.

Two notes. The 5.0 uses GM numbering, so a Ford order typed into it gives the pattern that order makes on GM cylinders, not what a real Ford sounds like. And the field accepts any order, including ones no real crankshaft can fire. For uneven spacing, open the 45° V-twin, which fires 405° and 315° apart like a Harley; the spec panel shows its firing intervals but does not let you edit them.

Frequently Asked Questions

What is a firing order?

A firing order is the sequence in which an engine's cylinders fire, written as cylinder numbers. A small-block Chevy's 1-8-4-3-6-5-7-2 means cylinder 1 fires first, then 8, then 4, and so on, one every 90° of crankshaft rotation. It is fixed by the crankshaft and camshaft, and the spark plug wires or coils have to follow it.

What is the firing order of a small-block Chevy 350?

1-8-4-3-6-5-7-2. Cylinder 1 is at the front of the driver side, the odd cylinders run down the driver side and the even cylinders down the passenger side, and the distributor turns clockwise. Every Gen 1 and Gen 2 small-block and the 396, 427, 454 and 502 big-blocks use the same order.

What is the LS firing order?

1-8-7-2-6-5-4-3, used by every GM LS (Gen III and IV) and LT (Gen V) V8. It is the small-block Chevy order with cylinders 4 and 7, and 2 and 3, swapped. GM adopted it mainly to reduce crankshaft torsional vibration and bearing loads.

What is the Ford 302 firing order?

The standard 289 and 302 fire 1-5-4-2-6-3-7-8. The 5.0 HO and 351 Windsor fire 1-3-7-2-6-5-4-8. Ford numbers cylinders 1-2-3-4 down the passenger side and 5-6-7-8 down the driver side. A 302 can carry either camshaft, so confirm which one it has before wiring it.

What does 18436572 mean?

It is the small-block Chevy firing order written as one number: 1-8-4-3-6-5-7-2. Chrysler's small blocks and Gen III Hemi, and many older AMC, Buick, Oldsmobile and Pontiac V8s, use the same sequence.

Does firing order affect horsepower?

Very little. In our simulator, four different firing orders on the same V8 made exactly the same power, 297.251 hp, in a model without crank vibration, cooling differences or exhaust pulse interaction. On real engines, Comp Cams' Billy Godbold puts a firing order change at "one percent difference if you get everything right", and OnAllCylinders reports one to two percent gains as common, partly from cooler-running rear cylinders.

Does firing order change the sound?

Yes. The order decides when each exhaust bank receives its pulses. A cross-plane V8's order gives each bank an uneven rhythm, the familiar burble, while an order that alternates banks gives each bank an even rhythm, closer to a flat-plane V8. Ford described its 5.0 HO order change as a sound improvement. In our simulator, which routes each bank's pulses to its own exhaust sound, the orders sound different while measuring identical power.

Can you change an engine's firing order?

Yes, with a camshaft ground for the new order, as in the popular 4/7 swap for small-block Chevys. Moving the plug wires alone does not change the firing order; it only sends spark to the wrong cylinders. The crankshaft limits which orders are possible.

How These Numbers Were Made

Every simulator figure in this article comes from one headless run of the simulator on 2026-10-04. For the order test we took three stock presets, the 5.0 L V8 (GM-style numbering), the 2.0 L inline-four and the 3.0 L inline-six, and entered each firing order through the same share link the Try It section uses, so the measured engine is the one the link opens. Each order got a full-throttle dyno sweep, 45 points from idle to redline, and a 30-second idle trace at 240 samples per second after 20 seconds of settling. The idle variation is the standard deviation of engine speed over that trace divided by its mean. The per-bank intervals come from the angles at which the simulator fires each cylinder, split by the bank each cylinder sits on.

For the spacing test we changed the firing angles of the 1,340 cc 45° V-twin directly, because firing angles are not carried in a share link, and measured the peak-to-peak engine speed over each 720° cycle at idle, averaged over the 30-second trace. Peak power comes from the same dyno sweep. The simulator models the crankshaft as rigid. It has no torsional vibration, no bearing loads, no cylinder-to-cylinder cooling and no intake distribution between cylinders, and its gas exchange does not respond to when neighbouring exhaust pulses arrive, so it cannot show why engineers prefer one order over another; it shows that the order alone, with those effects removed, does not change output, and how the order and the spacing change the rhythm of the exhaust and the crank. The real-world firing orders in the table are from the sources listed, not from the simulator.

About this article

Written by the team that builds the simulator and maintains its crankshaft, firing and exhaust-routing models. The firing orders, cylinder numbering and manufacturer reasons come from the parts suppliers, trade press and manufacturer sources listed below. The power, idle, ripple and per-bank figures are the simulator's and are labelled as such.

Sources and Further Reading

Related Reading