Introduction To Camshafts
If you’re unfamiliar with camshafts, you’re in for a treat. Maybe you’ve overheard mechanics talking about them, and you know they have something to do with car engines, but that’s about it. Well fear not, because you’re about to get a crash course in what exactly this part is and what it does.
Back To Basics
The engine in your vehicle contains two rotating shafts. At the bottom, you’ll find the crankshaft. When your pistons fire (as a result of pressing down on the gas pedal) it causes the crankshaft to turn. That keeps the pistons in a fixed position relative to one another. Because of the way the engine works, only one piston can be at the very top center position at a time. The crankshaft ensures that the pistons will come to that center spot in a specific order at the right time.
Now, when the spark plug fires, it causes the air and gas mixture to burn, and subsequently forces the piston down. When the piston descends, it turns the crankshaft at the bottom. The turning of the crankshaft is what causes the flywheel and drivetrain to turn.
At the top of the engine is the camshaft. It regulates the timing of the opening and closing of the valves. That ensures that when the spark plug fires, there will be gas present. The exhaust is properly emptied so that the air and gas mixture can be reloaded and the entire sequence can occur again (over and over).
The most critical parts are the lobes. While the camshaft is spinning, the lobes are the parts that actually open and close the intake and exhaust valves. They do so in perfect synchronization with the pistons. Interestingly, engine performance at various speeds is directly affected by the shape of the lobes. Therefore, engineers place great emphasis on their production, depending on what type of performance capabilities the vehicle needs to have.
The most common types of camshafts are as follows:
- Single Overhead (SOHC)
- Double Overhead (DOHC)
- Pushrod
Without going into too much detail, here’s a brief overview of the main types:
Single Overhead
This type of camshaft has one cam per head on the engine. In other words, a straight 6 (inline 6 cylinder) engine would have one cam, while a V-6 would have two (one for each of the heads).
Double Overhead
You guessed it; double overhead cam engines have two for each head. So, using the same scenario as above, an inline-6 engine would have two cams, while a V-6 would have four.
Pushrod
The main difference between pushrod cam engines and singe/double cam engines is that pushrod engines have the camshaft actually located inside the engine block, rather than on the head.
If you believe you may be experiencing engine problems due to a malfunctioning camshaft, you should see a mechanic as soon as possible. Even though I describe a lot of these systems in these columns, repairing the components involved requires a trained hand. Unless you’re experienced, check with your mechanic. Most of the problems that involve this part are best left to a technician.
