When it comes to V8 performance, General Motors has stuck by the pushrod engine. The iconic small-block V8 engine lives on to this day and shows no signs of coming to an end in the near future. But, pushrods are pretty outdated compared to dual-overhead camshaft setups. What’s so great about them?
Engineering Explained tackled five reasons why pushrod engines still exist, and their benefits check off a lot of boxes. The first is low-end torque. Pushrod engines have a habit of making lots of torque down low in the rpm range. It’s due to airflow and the fact pushrod engines normally use two valves per cylinder. This is also the reason pushrod engines don’t rev incredibly high.
The second is a relatively simple design. Unlike DOHC engines, pushrod engines are not complex in construction. In the engineering world, if a solution can be achieved with a simpler design, it just makes sense. Pushrod engines feature a single camshaft in close distance to the crankshaft, which means a belt, gear or chain doesn’t have to travel far to rotate the camshaft.
The simple design moves into the third and fourth advantages: size and weight. A pushrod engine’s overall packaging is much smaller and compact than a DOHC engine. Pushrod engines are also shorter, which allows engineers to place the engine further back in the engine bay to work on center of gravity.
Finally, cost. The video cites an interview with GM’s chief engineer for small block engines where the automaker said its pushrod V8 is about $400 cheaper than a DOHC design. Multiply $400 by hundreds of thousands of engines, and the cost benefit is clear.
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C7 Corvette Chief Engineer Tadge Juechter said how there was a discussion of whether to develop a DOHC-4v V8 for the Corvette before deciding to go with a OHV-2v design because it was much more compact, Juechter also commented on how the Corvette was almost a mid-engine car because of how far back the engine sat and actually said it wouldn’t have been difficult to have made the C7 Corvette a mid-engine car.
Why people want to get rid of it is beyond me
Yes, do replace them with electric motors. Only one moving part!
Or do you prefer a gas powered shaver, hand drill, tooth brush, and room fan? All have one moving part and last many years.
Surprise, Surprise the guy named “Volt Man” spewing nonsense.
@ volt fan
“shaver, hand drill, tooth brush, and room fan”
I wouldn’t mind having these LS powered.
I have a 1970 Chevelle with a GM Performance ZZ502 Big Block V8 and a 2017 Corvette Stingray. Both pushrod engines. Long live the pushrod v8.
Well pushrod V8 probably won’t meet future emission standards (Chrysler’s pushrod V8 is worse than GM’s)
Why did GM introduce the LTA with variable camshafts?
GM has even admitted they are nearing the end ad with out multi valves they will not meet future emissions.
The truth is GM was broke when everyone was making the change. It was cheaper and more profitable to keep these engine in place. In a way a negative turned positive as GM took the farther than expected.
But as standards increase they will make the change too.
“The truth is GM was broke when everyone was making the change. It was cheaper and more profitable to keep these engine in place. In a way a negative turned positive as GM took the farther than expected.”
Everyone? Their biggest competitor went to OHC engines in the late 80’s/early 90’s. Ford’s customers suffered through 2 decades of gutless 4.6 SOHC, 4.6 DOHC’s with worn out valve guides and burn valve seats, 5.4’s with so many issues they’re legendarily bad, and 4V 5.4’s that needed forced induction to keep up with those cheap pushrod V8’s.
>>”Pushrod engines have a habit of making lots of torque down low in the rpm range. It’s due to airflow and the fact pushrod engines normally use two valves per cylinder. This is also the reason pushrod engines don’t rev incredibly high.”>>
Well no.
The reason they don’t rev high is valve bounce. That’s why almost all OHC engines now have bucket cams running directly to the valves.
They have most of the torque in the lower range simply because they can’t rev high.
The airflow on a pushrod engine is _worse_ because the pushrods take up space that could be used by intake/exhaust valves. This was the original purpose of switching to OHC, before emission controls were introduced.
If GM engineering actually explained this and said low end torque is due to pushrods they should be fired or sent back to school. Torque is do to longer stroke PERIOD. You normally don’t rev a long stroke as high just due to inertia. But you could if it was designed properly, but cost of higher quality materials would never pay. It would be ideal and a much better engine if you had a long stroke OHC multi valve, V – something, turbo engine. But again pushrods have nothing to do with torque.
Believers that a pushrod engine can’t rev high should revisit the specs of the LS7. While I agree with the longer stroke mentioned above, this works in tandem of having a compact package allowing a larger displacement engine (an inherent benefit). Try fitting a 7.0 OHC engine in a Camaro. GM does use the OHC engine in their turbo applications (see 2019 Silverado drive trains).