#TechTip - Head to Head: Pushrods vs OHC

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 This leaves many thinking of older pushrod (OHV) engines as being archaic and outdated.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:

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

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?

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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Comments

Champford

I much prefer OHC or DOHC compared to pushrod. While I like the pushrod, the OHC system has so much potential and the pushrod system has a lot of potential…. to break.

02/19/2016 - 15:45 |
1 | 0

Pushrod is fairly reliable like in the LS and SBC engines but I prefer the DOHC making more power with less displacement. Example is the 5.0 coyote making near the same to more power than the 6.2 LS3 depending on year and being faster than it.

02/19/2016 - 16:07 |
1 | 0

The only time I’ve seen a pushrod system break is when cheap or improperly rated parts were involved and it’s usually a bent pushrod or a broken rocker arm. I have however seen a Mercedes DOHC engine snap it’s cam shaft into 5 peices

02/19/2016 - 17:54 |
3 | 0
The hoonigan

Rotary : because high RPMS yo

02/19/2016 - 15:57 |
32 | 5

So uhhh…. how are those apex seals doing?

02/19/2016 - 16:19 |
41 | 5

So uhhh…. how are those torque reading at low rpm ?

02/19/2016 - 16:40 |
7 | 2

DOHC also can reach even 12k :D

02/19/2016 - 16:56 |
7 | 0
Anonymous

OHC / DOHC would be my preference in a car or bike

02/19/2016 - 16:06 |
3 | 0
George Leluashvili

DOHC no doubt

02/19/2016 - 16:10 |
2 | 0
Comfused Miata

Ohc, no contest.

02/19/2016 - 16:35 |
1 | 0
Anonymous

OHC.

02/19/2016 - 16:37 |
1 | 0
Anonymous

As the owner of a SOHC chain V8, I’d say it depends on the application because of packaging. A OHC engines are much much wider and their OHV counter parts hence why the LS is put in everything. But if you got the space DOHC is the way to go because lets be honest. What race car is reliable?

02/19/2016 - 16:38 |
4 | 0
Anonymous

In reply to by Anonymous (not verified)

Ohc engines are taller not wider if anything they are narrower

02/19/2016 - 19:37 |
0 | 0
LetumSt

In reply to by Anonymous (not verified)

Can’t wait to build mine

02/20/2016 - 04:57 |
0 | 0
Anonymous

koenigsegg called and wants free valve to be on the list

02/19/2016 - 16:41 |
58 | 0
Anonymous

In reply to by Anonymous (not verified)

Damn beat me to it.

02/19/2016 - 16:58 |
1 | 0
Anonymous

In reply to by Anonymous (not verified)

This. So much this :D

02/19/2016 - 18:43 |
0 | 0
Anonymous

In reply to by Anonymous (not verified)

then fiat called with multiair in 2011….

02/20/2016 - 10:00 |
0 | 0
Josh Pizzy

Pushrod is not that much an older design, it only was invented a year or so earlier to OHC designs, Pushrods main advantages are in packaging, and ease of drive for the cam. For example, the GM northstar 4.6 is larger overall than an LS7. Neither is a bad design.

02/19/2016 - 16:45 |
1 | 0
Anonymous

Seems it definitely depends on the application. A 14,000 RPM superbike obviously needs DOHC, but a long-haul truck that needs a bulletproof low-RPM power plant could be better off with pushrods. Let’s not bicker over valve trains while some people still drive the Prius.

02/19/2016 - 16:56 |
10 | 0
Anonymous

In reply to by Anonymous (not verified)

Low rpm engines doesnt suffer as much as high rpm engine from the increased mass of push rods so modern isnt always better ;)

02/19/2016 - 20:18 |
0 | 0