#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 This leaves many thinking of older pushrod (OHV) engines as being archaic and outdated.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?
Comments
Dual Pushrod Cams
Hate to be that guy… Should be “Overhead Cam,” not “Overhead Valve” :(
Good find! Fixed the typo :)
I like OHC for one reason: keeping the pushrods in order is a pain if you’re not careful to explicitly label them. Other than that my SOHC Toyota engine with a timing chain is practically a pushrod engine. Thing hates to rev
For being “old and archaic,” people sure do swap pushrod LS and Ford 302 engines into a lot of things. Why? The OHV configuration offers a lighter, shorter, narrower, and simpler platform to work with than an equivalent OHC engine. Plus, I’ve never heard someone say that LS engines don’t make enough power. And, with the right valvetrain components, you can spin them to the moon. I had a 408 stroker that I shifted at 7,000.
Want to hot rod it? Go for OHV. Want to buy it new and keep the engine mostly stock? Buy whatever you want. The new Ford 5.0 and 5.2 are pretty impressive; but, at the end of the day, the pushrod motors will almost always be more user friendly and simpler to work on.
Can we have a:
Timing chain/Timing belt/Timing gear/Electronic timing thread next?
details ……….
In most respects, most CARS with ohc have an efficiency edge over those with ohv, so that would influence my decision heavily, but there are other factors to consider, particularly on older engines.
Well it’s hard to say I have both a 2.3 DHOC in an IVECO and a OHV in a MGB GT. the power outputs from a DHOC are greater
I love OHV V8’s with how light and simple they are compared to S/DOHC engines. Also the amount of torque they have is awesome. Although I prefer the higher revving OHC engines.
OHV all the way!