Interesting DOHC vs. pushrod 500+ motors

[Paul Workman]

Originally Posted by todesengel

The point wasn't missed.

Oh, oh yes it was missed, but it's my fault for being vague though... But, your SC mustang makes a good point too! (I'm just making conversation here - not impugning anyone, OK?)

What I was obliquely pointing out was, how power is made in view of upcoming restrictions (gas mileage) displacement and efficiency are most certainly going to be relevant for production vehicles. And, cubic inch for cubic inch, the DOHC 4-valve configuration with it's independently and dynamically controlled cams and "lifters" breathes soooo much better and has sooooo much more flexibility and output potential than single cam, OHV designs! The DOHC/4-valve approach - is but one example of why in my gut I feel GM is screwing the pooch by chasing single cam OHV technology any further - at least in the long term. (Course, who knows what is going on behind the curtain in GM's engineering shop?) And, when coupled with a 35 mile/gallon (or more?) in the near future, cubic inches to get hp (a la the LS7) may be a thing of the past. Power/displacement, according to my crystal ball, WILL become a relevant factor if output is to remain steady with efficiency a mandate.

To your supercharger point; that is one option that certainly works in the short term. For you or me, or many (most?) ZR-1 drivers on this board, maintenance of such a setup might not be a factor. But, I'm referring to the unwashed masses of Corvette buyers that are needed if the brand is to survive so we car nuts have the luxury of picking and choosing and playing with the picks of the litter, so to speak. Supercharging has been around since WWII, and even Dave Mclellan fooled around with it back in the 70s. Yet, to the casual observers like us, when it came down to "absolute" reliability and performance, even the Callaway approach - that was readily available to GM - was pushed aside in favor of a "better" power plant scheme for the ZR-1.

Well, I'm not a mechanical engineer, so I'm out on a limb here. But, from where I sit, the evolution of the internal combustion engine, as it applies to the Corvette in particular, took a huge leap forward in the form of the LT5. High performance (piston) aircraft engines and motorcycle engines (opposite ends of engine displacement) are often built with 4+ valves per cylinder, and the aircraft example is built with superchargers to boot; where (in both cases) power efficiency IS a factor. So, was the reason GM shelved the DOHC multi-valve concept (in V8s at least) a failure of technology or just expedient?

There was this company that made oaken buckets. Sales started slipping when home builders began to use pipes to carry water to the houses. So, the oaken bucket company decided to combat slumping sales and make the best quality oaken bucket ever. The best oak, topped off with the finest brass rings and handle were produced. And, for a short time, sales did pick up and the company was assured it had made the right decision.

But, eventually, sales plummeted and the company went broke, in spite of making the finest oaken buckets ever produced. They simply failed to realize that people did not want buckets; they wanted water. The bucket was (at the time) the way to do that. But, technology had moved onto a more efficient method of getting water from the well to the sink.

I don't know if the DOHC 4+-valve NA motor is the answer. But, in my gut I feel GM is making the finest "LSx" oaken buckets ever! (was my point).

Pop some popcorn and enjoy the show. The next 5-10 years...are going to be interesting, methinks!!

P.