LS7...not so good
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Joined: Jul 2001
Posts: 1,808
From: FL/MI
Re: LS7...not so good
Originally Posted by Hoodshaker
From a strength stand point, there is no question as to the superiority of the forged piston. However there is a weight penalty. That article was to address your point that the cast piston would require reinforcement that would make it heavier than a forged one. Perhaps that would be true if you were trying to make a cast piston with the exact same strength as a forged one. The benefit of a hyperuetectic is that it is stronger than a regular cast piston, yet lighter than a forged one. That seems about right for this application. I don't think a naturally aspirated LS7 that is not detonated will have a problem. If you run it way lean, you may have a problem. The factory tune will not allow this. But undoubtedly some of us that like to mod our cars will make mistakes like poor aftermarket tunes or poorly designed/underfueled forced induction and nitrous systems. That's our fault, not a design flaw of the car. So in conclusion I think they had to decide whether to go with a lighter piston that can't take as much blatent abuse vesus a heavier one that would have forced them to to lower the max rpm to protect the assembly, and miss out on some hp because of it. The slower revs and extra stress on the crank isn't worth it when the hyper is strong enough unless severely abused. Anything could be stronger. A lead parachute would never tear, but I think the benefit is outweighed by the penalty.
More on the subject that speaks directly to cast vs forged. http://www.glmmarine.com/castvsforged.html
More on the subject that speaks directly to cast vs forged. http://www.glmmarine.com/castvsforged.html
Nothing wrong at all with high silicone short skirted pistons. Spraying a motor not buit in all aspects for Nitrous is a mistake. Going forced on induction is a mistake on a motor not built for it.
Good job on pointing out what should be obvious.
Last edited by 1fastdog; Dec 6, 2005 at 07:44 PM.
Registered User
Joined: Feb 2003
Posts: 439
From: Northern VA
Re: LS7...not so good
I'm guessing that hypers and their tight fit were almost a requirement to meet cold-start emissions. 2006 regs are a lot tighter than 5.0 days.
EDIT- on the matter at hand, there always seemed to be a guy or two at Corvette Masters that spread some mildly outrageous rumor, to make you think he's "in the know." I always took it as "whatever." Robbie was always straight with me, though- gave me some good info on piecing an AC system together for my car (years and years ago).
EDIT- on the matter at hand, there always seemed to be a guy or two at Corvette Masters that spread some mildly outrageous rumor, to make you think he's "in the know." I always took it as "whatever." Robbie was always straight with me, though- gave me some good info on piecing an AC system together for my car (years and years ago).
Last edited by Todd80Z28; Dec 6, 2005 at 11:08 PM.
Registered User
Joined: Aug 2003
Posts: 3,011
From: Exton, Pennsylvania
Re: LS7...not so good
I am not sure about the clearance for the LS1, but I can tell you that when I go to start up my car in this 20 degree weather, my LS1 has too much side clearance, at least in what appears to be cylinder 8. That thing slaps its *** off when cold. I can really see GM using the hypereutectics to keep the noise down on the engine, because the amount of noise my engine makes in the cold is unreal, and I can't imagine having the same amount of noise present on a $65,000 car.
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Joined: Feb 2002
Posts: 2,428
Re: LS7...not so good
I think some of us have become too critical GM. If your doubting the z06 engine, you'll doubt anything GM ever makes. So far all the info on this engine's "problems" is just word of mouth...gossip.
Come on guys, theres better stuff to be worrying about, like what color the 5th gen display car will be.
Come on guys, theres better stuff to be worrying about, like what color the 5th gen display car will be.
Registered User
Joined: Aug 2003
Posts: 3,011
From: Exton, Pennsylvania
Re: LS7...not so good
My LS1 engine may slap its *** off when I first start it up, but it has never consumed oil, which is a known problem for LS1s, and runs reliably everyday, no matter how much I abuse it. I would love to have an LS7 in it, whether it slapped or not. I just can see someone getting very pissy over putting down $65,000, and having a noisy engine. Hell, GM may very well have gone with hypereutectic pistons because they are cheaper. I am not trying to say I know why GM did, but I would bet that on a motor like the LS7, they would not go hypereutectics for no reason, and I would doubt that it would be cost. The engine has Ti connecting rods for Christ's sake, and I know that even though the Ti rods in the LS7 are only forged (I believe most aftermarket Ti rods are billet), they still have to cost a sh*t load.
Registered User
Joined: Oct 1998
Posts: 3,144
From: Jackstandican
Re: LS7...not so good
Originally Posted by Aaron91RS
hyper crap pistons don't take to nitrous or blowers at all.
The Ford 3.8L supercharged SC's use hyper-u's.
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