Jim Smart
November 1, 2002
Photos By: Mustang Monthly Archives

We have introduced you to the workings of a single cylinder. If Mustangs had only one cylinder, there wouldn't be enough power to get the job done. Since 1964, Mustangs have been getting the job done with four, six, and eight cylinders. From 1964-'73, Mustangs came standard with six cylinder engines-with six cylinders positioned in a row along a long crankshaft.

Eight-cylinder engines have always been optional, with eight cylinders in a "V" configuration on two banks of four cylinders each. Beginning in 1974, standard Mustang power was four cylinders in a row. When we line up four and six cylinders in a row, we call it an "inline" engine. Economy cars are traditionally equipped with inline fours and sixes. These engines make a buzzy sound. V-type eights, or V-8s, make a throaty sound much different than inline engines. If this doesn't make sense to you, think of it this way. NASCAR Winston Cup racing consists of V-8 engines that make that powerful roar. Busch Series and Grand National racecars get power from V-6 engines that buzz like a swarm of bumblebees. From 1974-'79, 1982-'86, and 1994-'03, six-cylinder Mustang power isn't inline, but instead a V-6, with two banks of three cylinders in a "V" formation.

Stop Cocks And Bumpsticks

How do we get the fuel/air mixture and exhaust gasses into and out of the combustion chamber? We do this with poppet valves (stop cocks). One valve allows the fuel/air mixture in and another lets hot exhaust gasses out. Poppet valves are shaped like large nails with huge heads. The tapered valve heads close against a tapered seat in the cylinder head to stop the flow. The closed valves seal the combustion chamber between intake and exhaust cycles.

How do poppet valves work? Poppet valves are held closed by springs known as valvesprings. The camshaft (bumpstick), a rotating shaft with a series of eccentrics or lobes, opens the valves in time with the crankshaft. The crankshaft and camshaft are tied together with a timing chain and gearset at the front of the engine. Camshaft speed is normally half that of the crankshaft. This makes perfect sense when we consider the four cycles that give us power. The crankshaft makes two complete revolutions for every revolution of the camshaft. Another way to look at this is we have two complete revolutions of the crankshaft for the four cycles. When the crankshaft is whirling around at 4,000 rpm, the camshaft is spinning at 2,000 rpm.

How do cam lobes open valves several inches away? They do this via lifters, pushrods, and rocker arms. The lifter rides on the cam lobe. The pushrod sits in the lifter and transfers linear (back and forth) motion to the rocker arm at the cylinder head. The rocker arm is a lever that takes the pushrod's linear motion and transfers it to the poppet valve. The poppet valve is opened by the cam lobe and closed by the valvespring.

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Light My Fire

To have power at all, we need a way to ignite the fuel/air mixture once it is inside the combustion chamber. We do this with a timed, high-voltage spark. The timed spark comes from the ignition system, which is tied to camshaft and valve timing. Mustangs prior to 1996 have a distributor, which times the spark at compression stroke as the piston nears the top of the cylinder. The distributor channels high-voltage electricity from the ignition coil (an electrical transformer) to each of the engine's spark plugs. Each cylinder (combustion chamber) has one spark plug. If we have a six-cylinder engine, we have six spark plugs. A V-8 has eight.

When we think of a multi-cylinder engine as four, six or eight individual engines, it becomes easier to understand spark timing. In a V-8 engine, for example, we have eight individual cylinders firing at eight different times in sequence. No two cylinders fire at the same time. They fire in a sequence known as the firing order. Your Mustang's 289ci V-8 engine, for example, has a firing order of 1-5-4-2-6-3-7-8. If you study this firing order, cylinders fire back and forth across the two banks. Cylinder 1 fires first. Then cylinder 5 on the opposite bank. Then back across to cylinder 4. Then across the same bank to cylinder 2. Then over to the opposite bank to cylinder 6. Then back over to cylinder 3. And finally cylinders 7 and 8.