#TechTip - Head to Head: Pushrods vs OHC

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Overhead cam (OHC) engines have recently become the go-to for modern engines. This leaves many thinking of older pushrod (OHV) engines as being archaic and outdated. So what are the advantages of each?

Pushrod Engines:

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Pushrods are simple in certain aspects. There is only one camshaft, and the timing configuration is easy (usually a single chain from the crankshaft to the cam). Because pushrod motors often use timing chains, the maintenance intervals for timing components are much less frequent than the timing belts that OHC engines are so fond of. Also, since the cam is located within the engine rather than on top, it leaves a lower center of gravity than its OHC successor.

That being said, pushrods inherently contain a lot of moving parts. This can be seen as an opportunity for more things to go wrong, and it adds mass to the valvetrain, which becomes an important factor in very high rpm use.

OHC

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Overhead cam engines have some advantages as well. Because there are far less moving parts, their potential for high rpm is increased. Dual overhead cam (DOHC) platforms also benefit from an improved spark plug location because of the location of the cams. Due to cam placement, it is possible to place the spark plug directly in the center of the top of the combustion chamber, creating a more evenly distributed and complete burn. It should also be noted that swapping out camshafts in an overhead cam engine can be much less of a hassle due to the fact that they’re located at the top of the engine.

Disadvantages are the sheer number of cams, which adds its own factor of complexity as well as the common use of timing belts with OHC applications which are more prone to wear/failure than their timing chain predecessors.

So which is better?

#TechTip - Head to Head: Pushrods vs OHC - General Mechanical Advice

Each of these setups has its own unique advantages. While the pushrod valvetrain may be older in design, it does hold its place in the market for valid reasons alongside its OHC brother.

Which configuration do you prefer from the two?

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