pushrod vs. ohc

And this brings us full circle.... the "antiquated technology" you refer to makes more power, is cheaper, more reliable, smaller, lighter and requires much less maintenance than what you consider to be "better" technology.

We could make car bodies from titanium. It would be heavier than aluminum. It would be more expensive. It wouldn't hold up a well. It would be much more difficult to form. It would have many drawbacks and wouldn't be nearly as good as aluminum. But it would be "newer technology". Therefore it's better?

Again - if pushrod engines are antiquated and only sold in the USA because Americans are too stupid to understand the benefits of an OHC engine, then why does the pushrod engine cost less and make more power in a package that is smaller, lighter, more reliable and requires massively less maintance?

Are engineers at companies who predominantly make OHC engines simply too stupid to figure out how to beat the antiquated pushrod engine? must be!

 

In engineering decisions it often does not make a whole lot of sense to design strictly to one design criteria (like hp/liter). Why are you presenting this as a valid engineering argument?

Perhaps the single most valuable engineering criteria is cost. And that's one where OHV is very good.

 

UI had no idea this would start a Holy war. Maybe it should be moved to politics and religon, ha ha. Seriously thanks for all the info.

 

Weight is not that big of an issue if your making more overall power per cube. Seriously, a DOHC head does not weigh a great deal more than a crude OHV head.

Overall size usually isnt any greater issue than the size of the induction system. A DOHC head is only marginally larger in cross section than a simular OHV head.

Complexity is also more or less a wash. In fact, a cam in block engine can turn into a real nightmare if you need to remove it with the engine in the car. DOHC engines have existed for over 100 years, and today almost all motor vehicles in the world use them. If its too complicated maybe those manufactures who are still trying to catch up to the 1940's should stick to tractors and lawnmowers.

Cost of the engine is almost a non issue today. Cars are incredidbly expensive, and a great deal of that cost is in electronics, suspension, crash protection, luxury packaging, sound systems, etc... The engine is but a small percentage of the "big picture". If Ferrari could give us engines over 10 years ago that produced 109 HP per liter naturally aspirated that meet all worldwide emissions standards, then the BIG 3 should be more than able to offer that antiquated performance technology today. So trying to argue for low technology car engines in a $108k Corvette is just a little bit silly.

At 6.2 liters, if that motor were making 109 per liter it would be making 675 HP. And nothing short of that is anything to get exicted about. But that was yesterdays technology. Todays 458 Italia produces 126 HP per liter. If GM's 6.2 liter small block Corvette were producing that level of power, we would see 785 HP.

OHC, and DOHC engines ushered in the last century. After more than 100 years, maybe its time to join the 21st century? Really, my stupid pressure washer is OHC. There is no excuse for our cars not to be.

 

Maybe it does belong in Politics & Religion, because that was just a religious rant if ever I've heard one; denying and belittling any suggestions or facts that run contrary to one's own belief.

 

So you're response is "none of that matters"? Can't argue with that logic.

 

I never said it doesnt matter. But when you plunk down $108K for an American made sports car that purports to be a "world" sports car, and is aimed at taking on the worlds greatest sports cars, it should have a bit better technology than something like stoneage pushrods.

I think some of this is sorta like the Ford and Chevy wars, people trying to defend thier position out of pride rather than science and honesty. I like Vipers, I think theyre a very cool car, and 500 HP is really nothing to sneeze at. I wouldnt mind owning one. But I would never try to pass the thing off as anything high tech; Its crude caveman technology. 500 HP from an engine 8 liters in size is truly pathetic in the 21st century, but thats what you get using 1950's large displacement pushrod technology. And 630 HP from a Corvette is respectable as well, but still nothing under the hood to get excited about. Not quite as caveman as a Viper, more Cro-magnun vs Neanderthal. An Italian couldnt win a fist fight with either one, but they could never catch him or outsmart him either. More "brains over brawn". If ya'll get more excited over a big thumpin pushrod motor than you do a Ferrari motor, I do appologize.

 

Of course cost is an issue, as is complexity, as is engine height, as is engine width, as is maintenance.

And comparing a Corvette ZR-1 (LS7) to any Ferrari is just plain silly when the Corvette needs no major engine maintenance during its first 100K miles and the Ferrari need tens of thousands of dollars in engine maintenance in that same time period.

But does that make the Corvette better? In some respects certainly, but in others most definitely not. And thus is the difficulty with the entire argument as their are a myriad of reasons why the engineers and designers utilize one engine over another.

Shiny Side Up!
Bill

 

Engineering is all about compromises.
Pro/con.
Tradeoffs.
Cost/benefit.
Most of your absolutes come from the manufacturing side and the government.

Both kinds of engines can be well developed and deployed.

 

GM has done wonders building disposable cars that require no maintenence for the life of the car, and they pretty well set that life at 100K miles. Ferrari have done equally well at selling a lot of excessive service at incredibly exorbitant costs. But we can be assured that if you didnt do any work on a Corvette for 100K miles, the service work to put it back to like new condition would be extremly expensive. In that regard it doesnt matter who builds what, its all going to need service sooner or later, or junked, and sooner, rather than later, has historically always cost less over the long haul.

The pushrods vs OHC argument, however, is virtually a non issue regarding maintenence. OHC designs can, and have been designed to run many hundreds of thousands of miles without any maintenence whatsoever. Its the camshaft drive mechanism coupled with unusually high engine speeds, not the camshafts or followers, that causes Ferrari owners grief.

 

At $108K, An assembly line built American sports car shouldnt offer any compromise.

 

What?!?! Get over yourself!

All cars have compromises, regardless of cost.

Shiny Side Up!
Bill

 

Well said. I keep a sign in the race shop...

Good, Fast, Cheap... Pick two!

Rick

 

Certainly the 'Vette will need maintenance over it's life, but the engine will need oil changes and spark plugs, not 10K timing belt jobs!

Absolutely! And their are lots of manufacturers that make well built products regardless of their choice of valvetrain. The Corvette is most certainly not the end-all-be-all of sports car design. It is built to a price and a set of guidelines, and it performs very well for that price and within those guidelines, just as every other sports car is built to a price and a set of guidelines. From Porsche to Ferrari, each does its job well within its own micro-niche. The competition among them is more about the micro-niche than it is about each cars actual performance.

Shiny Side Up!
Bill