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Exhaust Stroke/Blow
The exhaust valve opens and the piston travels upward to blow the burned fuel and air mixture out of
the cylinder, through the exhaust manifold, catalytic converter, and muffler, and out the tailpipe.

The pistons in the engine all work in sync to provide ongoing rotational force. Each piston is
attached to the crankshaft, which is attached to the drivetrain. Depending on how many cylinders the
engine has, the firing order varies.

The valves (which regulate the intake and release of air), fuel, and exhaust also operate in sync.
They are controlled by a camshaft, which is attached to the crankshaft by a timing chain or timing
belt for proper piston and valve positioning. This is critical, because without a timing chain or belt,
valves and pistons can’t operate properly and can potentially collide with each other, causing serious
engine damage
In its basic form, a combustion engine is a rather crude way of generating energy. It’s essentially a bunch of
explosions happening inside a hollowed-out piece of iron. But take a closer look and you’ll quickly learn how
refined an engine really is.


Valve Cover Gasket for modern engines, a full engine cycle is four strokes, which refers to how many times a
piston must travel up and down inside a cylinder during the cycle. The engine draws in precise, micro-
measured amounts of fuel and air through valves, compresses them, combusts them, and releases them.
These four strokes are commonly referred to as suck, squeeze, bang, and blow.

Intake Stroke/Suck
The intake valve opens and the piston moves downward to suck in air while the fuel injector introduces fuel.

Compression Stroke/Squeeze
The intake valve closes and the piston travels upward to squeeze the fuel and air mixture.

Combustion Stroke/Bang
The spark plug fires, creating an explosive bang in the chamber. This drives the piston down, releasing the
energy required to move the automotive.
Engine Repair and Service

6014 NE 112th Ave
Portland OR, 97220
E&A Auto Repair