5 Reasons Pushrod Engines Still Exist

Pushrod engines typically use two valves per cylinder, and as a result this engine style is often mocked when used in modern vehicles.

Engineering Explained

09 May 2018

Pushrod engines typically use two valves per cylinder, and as a result this engine style is often mocked when used in modern vehicles. Fewer, larger valves results in more reciprocating mass which can lead to valve float, and less airflow at high RPM from the reduced area of the valve openings versus four valves. So why are companies like Dodge still making Hemi engines, and Chevy still making LS engines, both of which are two-valve pushrod setups?

Well, simply put, pushrod (OHV) engines have quite a few advantages over their DOHC counterparts. Whether it’s the size and compactness of the engine, the simplicity, or the cost, there are real performance benefits to using a two-valve, single cam V engine. As the saying goes, if it ain’t broke… Check out the video for five detailed reasons why these engines are still made.

Comments

So , a good idea to compare the different characters of both ohv and dohc engines will be to put on an engine dyno an LS7 and a Mercury sb4 , basically same block , same dry sump , same crank and rods and even pistons but one topped by the stock chevy casted aluminum heads and the second by a completely new 4 valve head , developed using the stock ls cam and placing a new pulley to move the four cam instead . This will give us a complete chart of how much an engine changes its performance by a variation of the cylinder head alone :)

But then valve lift and duration etc plays a factor, keep them equal or go for most power with each? Would be an interesting test :)

You know whats sad. The fact that one day there will be a video like this explaining why there are still petrol engines in the road. 😢

Easy way to compare. BMC A series bottom end. One with an Arden 8 port pushrod head, and another with a KAD 16v head. Identical cam specs, both with EFI etc. Only difference is valve actuation.