Hi,guys.I was reading either Corvette Fever or Vette magazine very recently(I'm a subscriber to both),and I found out a little bit of info which,to a point,was a little disappointing.Our new C6 Z06 has cast aluminum pistons,not forged,as should have been the proper way.Funny how GM still,to this day,lets the bean counters get away with such stupid things.Especially with the Vette,their flagship!I wonder what the Vette's chief engineer thought when he was told what a dumb bunch of accountants said could or could not be in the top GM car.As powerful as it is (mid 11's in the quarter),just imagine if the actual engine hardware was a trifle more fortified.I do hope the bean counters don't short-change the true enthusiast like you and me in the future,just to save 5 or 6 dollars on the so-called "bottom line".If there's been a car that deserves better,it will ALWAYS be our car,the CORVETTE!!! Always your friend,Joe. LONG LIVE THE C4!!!!!

 

Those Bastards!!!

 

I'm not surprised or really disappointed, and I imagine the pistons are not only cast, but cast hypereutectic aluminum for the tight fit, emissions, and lack of piston slap.
http://en.wikipedia.org/wiki/Hypereutectic_piston

From my perspective, this is perfectly okay -- the way the universe does and should run:
First, GM products (and Ford, and Porsche, etc.) are designed to a budget. If cast pistons can do the job -- and I assume they can because GM seldom makes mistakes like that -- then they are fine with me. GM is selling a 505 HP super-performance car at a bargain and I think it is unreasonable to expect them to do all that and provide the parts that will make hot-rodding it to 600+ easy. If they start making things stronger and better than they have to be, soon your $75,000 wonder car costs $150,000.

But I bet that here, forged pistons really can't do the whole job:don't forget, forged pistons have their downside - besides the emissions issue, you are almost certain to get piston slap when the engine is cold: early LS engines were notoriuos for this even with hypereutectic pistons -- GM revised the piston design after about '99, but that was a sign this engine is prone to problems like this anyway (probably due to the type of metal and design of the block casting).

I thinkGM made this decision mostly for this reason: forged pistons can cause excessive cylinder wear, etc., particularly in a case like the LS7 (or a C5R). The 1/2 inch greater stroke required to get the full 427 cubesputs the stroke/rod length ratio right at the limit most people think is tolerable, so during part of every revolution the piston is really being slammed against the side of the cylinder. A forged piston, with its harder metal and slightly smaller diameter when cold, would cause excessive wear. A softer and faster expanding hypereutectic cast piston will cause much less. GM probably felt that it could not meet longevity (100,000 extended warranty exposure costs) and customer satsifaction (it would start blowing a bit of smoke when cold at maybe 35,000 miles) goals with forged pistons.

I accepted all these problems when I had my C5R built up with forged pistons because I had to,but I always let the engine warm up at idle before driving it and I just accepted the fact that the cylinder walls will only have about half the life (60,000 miles if I baby it, 35,000 if I don't) that one would normally expect: power, and light weight, cost gobs of money and require compromises.

And finally, someone is bound to ask, "then why did Ford put forged pistons in the '03 Cobra, a car built even more to a budget?" Answer, with the supercharger, they no doubt needed them for the car to have any longevity. And remember they used aniron block (a damn heavy one, too) -- so wildly different rates of heat expansion were not an issue, and cyulinder wear was much, muchreduced.

 

Although dissapointing, and maybe not the right choice, or i should say there could have been a better choice, we may as well face it. They are cutting where they have to and trying to build the best car they can for a very good price. It's a shame, but you see it more all the time, sometimes it works somtimes it don't. We could just hope the engineers have did their jobs, and they made the right decision.
In the end, they strive for quality, but the bottom line is, It has to be profitable.
Plain and simple.

Look at FOMOCO, the worse quarter in years, How can they last losing BILLIONS $$$ like that?

 

Really guys this persepctive that there is some insidious, lurking force diluting quality by "cutting" is just plain wrong. Every car (except maybe the Bugatti -- and its about to bite the dust apparently) is built to a price target. So if you want to put something in, ask yourself: what will you take out?

Suppose for a moment you had been the ZO6 engineer. You had a target price for the car - let's say $69,995 list. There's profit (your company has to stay in business) and so forth, but this leaves, say, $30,000 for materials (and $15,000 for gross profit before taxes, and about $25,000 for assembly machinery and labor and set asides for warranty, and marketing and advertising, etc.).
So you put forged pistons in ($40 extra for materials). Now you have increasing cylinder wear so you have to increase the warranty set aside per car (say $80) or maybe you can get by usinga costlier block casting material to reduce rate of wear (say $50 more). And then you have to have cold start emissions equipment to get by the EPA requirements (probably secondary cats or some other active-heating system, which is nasty, but let's say we find a cheap way out, for just $150 more). Net cost is about, oh, say $250. Where are you going to find $250? You can't increase the cost of the car: do that too often and as i said earlier it becomes a $100,000+ vehcile.
So what couldyouremove to save the $250 you want for the forged pistons? Well, you could substitute the standard C6 steel hydroformed frame for the special aluminum one used in the ZO6.You could nix the fancy exhaust with its active by-pass valve muffler.Youcould "de-content" the interior of some of those nice upgrades that make the C6 interior so much better than the C5s. Any of those ways would problem cut cost by that $250.
Again, the car does notneed forged pistons -- they would not contribute anything to performance, light weight, or anything you can tell by driving it, os in terms of the overall car, you've just reducing its appeal and potential, all so you can have something that is "better" only in a sense that is totally unimportant to the car.

Maybe its because I've been an engineer for 40 years and banged my head against similar problems over and over again. But I'm just terribly impressed with the overall engineering of the ZO6, particularly the LS7,like few other cars - to me it is a simply brilliant balancing of tradeoffs to a budget. I give GM an A+ grade andcredit for doing what needs to be done, not what people think they should do.

 

Just think what they could build if the average wage wasn't $32.00 an hour. Kinda like Athletes.... way over paid for the work performed.

 

I agree 100% on these overpaid athletes. So the philosophy here is the more you pay them the better they are.
YEA RIGHT!
The need a complete re-tune of all major sports.

 

To all who responded,and Mr Willis,my friend.If I'm not mistaken the new Z06 has a magnesium engine cradle,while the standard Vette(Z51 or not)has an aluminum one,or maybe steel.The reason I posted this comment is simply because GM still short-changes its cars,the Vette included,without realizing that maybe,just maybe,we can be more than willing to pay a few extra dollars for a car that can demonstrate that it has the quality of assembly that is needed nowadays to compete with the competition(namely,Toyota;do you all know that they will become the #1 auto maker?Why?Because they do not skimp on the DETAILS!!!!)Engineering-wise,well,few cars can ever top the Vette,but why cut it a tad short by using a few parts and pieces that de-grade it,to a point,when all the GM brass know that we're always willing to pay for just that little bit of extra effort in making a better quality car than the so-called competition can ever make?The Vette still rules,but I think the accountants will destroy it and eveything it always has been,if they get away with it.Let's not let them do it!!!!LONG LIVE THE C4!!!!

 

I don't think GM did short change the car: I admire the choices they made (magnesium cradle, cast pistons) to meet there budget price target for the ZO6, but of course you will always have people who want to pay more for a bit more quality or content (me, you) and folks you want to pay a bit less for just a bit less (a neighbor you found the price a bit too steep).
As I have pointed out before in another thread, from the "GM wide perspective" if you really want a $100,000 vette with $100,000 quality, they want you to buy the 469 HP Cadillac XLR-S, it's a 'vette underneath, but with a higher quality body and interior build, and a very "high-tech" engine. It is a bit faster than a standard C6 (I've driven it, it really is) butnot as fast as aZO6, although achange of SCR pulley size anda bit of reprogramming would take care of that, and aftermarket tires would bring handling up to 'vette standards. Quality (particularly of the interior) is just superb, it has all the engine technology you could want, and it hasthatsteel retracting top. It just costs half again as much as a ZO6.
Or of course, if you want quality you can do what I did, which is to buya Porsche: definately not what GM wanted, but while I really like the XLR-S, as I told the salesman, "I already own a 'vette."

 

I've got an idea !
Why don't we email GM over @ Bowling Green?
My experience with them is that they are always fast to respond and eager.
Just my humble opinion.