Commentary: Pushrods?

Photo (c)2012 General Motors

Imagine my surprise when General Motors introduced the horse before the cart.

The introduction in question was GM's unveiling of the fifth generation Small Block V8 that will reside in the upcoming C7 Chevrolet Corvette. Normally, an engine is introduced alongside the new car. Somehow, there was an impression that we could not wait until January 13, 2013 for the new heart to be discussed alongside its new body.

It was an interesting move, to say the least. Yet, it was shrewd. GM did post up the C7's revised crossed-flags logo days before it whipped off the wraps of its new 6.2litre V8.

What is different about the Gen V LT1 V8 is all geekery. It appears to be the same block, but plenty of work was done on and around it to create a true sports car engine. GM added direct fuel injection, active fuel management that cuts off cylinders at certain speeds and a new variable valve timing system to the new engine.

The result is a promised 450 horsepower and potential 0-60MPG times of below four seconds. Impressive, I must say…

However, I took a look at the cutaway illustration of the engine and found something rather discerning. It still has pushrods.

Pushrods? With just two valves per cylinder?!?

Discerning? At first, yes. You would think for GM to leverage the Corvette into the supercar game it would have to move the single camshaft from below the crankshaft up to the cylinder heads and double the amount of valves over the cylinder – similar to its competitors. I envisioned the C7's engine to be this 5.5litre V8 currently used in their sports and endurance racecars, but the added overhead camshafts and efficient valve system we expect from a finely engineered supercar.

Alas, no. Finding this out needed some form of venting. I took it to Facebook. At that point, I could not argue with my colleagues who supported GM's decision to keep the pushrods in their 450-horsepower 6.2litre LT1 Gen V Small Block V8. I should never argue with those with deeper knowledge of the engine than I.

I will admit that I should not have been initially harsh on GM about keeping the pushrod design. One of my favorite engines of all time has them – Chrysler's modern HEMI. That engine also came from a series of geeked-out enhancements that resulted in a renaissance of performance at Chrysler. How could I have been blind knowing how much I love the absolute power coming from a similar pushrod engine?

By keeping the old tried-and-true overhead valve/pushrod from a single camshaft design dating back to World War II, it kept the C7 "real." To induce 450 horses is good enough in my book. It keeps the 'Vette in the game, if you compare it to its direct competitors – the Porsche 911 Carrera S. That figure may not be the magic 500 horsepower that is now the threshold for supercar status, but why do you need that when there might be a new ZR1 (or similar model) being planned for the C7. Or, will there be a supercharged version of the LT1 to play with the McLarens and Ferraris?

Perhaps GM played this card correctly. We had some many questions about the C7. We speculated this thing to death. Now that we know what will lurk underneath its hood, we want to see the rest of it. We want to know if interior quality will equal the Porsche, Ferrari or McLaren. We hope that it looks like 'Vette with its front-engine/rear-drive design, long hood and blunt rear end. We expect a ride/handling package that is considered one of the best in the world – taking the Alps, as well as Interstate, even better than it predecessors. We just want ensure that one of our two supercars will be still be considered part of this high performance game of knothole.

To almost loose faith in the ‘Vette because of an old piece of engineering that continues to evolve thanks to the latest in technology and engine construction. How dare I kvetch about pushrods? Never again…

When the C7 finally shows up on stage at Cobo Hall in Detroit on January 13, all I can hope for is this: It better pretty damn good.

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  1. If one says 450 is not enough horsepower think about this. The when the C5 Z06 corvette was introduced it only had 405 hp. The base model C7 LT1 engine will best that by 45 horses. That is considerably more power in what will probably be a car as light or lighter than the C5 Z06.

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