Forged or ... not ?
Thread Starter
Pro
Joined: Jan 2009
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From: Austin Texas
Forged or ... not ?
Check out the piston section on page 73 of the link below
http://www.s-series.org/htm/tech/GMP...ts/070-075.pdf
It says in the intro to that section, that the pistons are forged.
Someone recently suggested 10159438 pistons are not forged. My read is that the 10159436, pictured in the section that says they're forged, are the stock diameter version of the 10159438, which is a 30 over piston of the same.
any thoughts / clarifications ? Are these pistons forged as the GM catalog says, or not forged ?
thanks....
http://www.s-series.org/htm/tech/GMP...ts/070-075.pdf
It says in the intro to that section, that the pistons are forged.
Someone recently suggested 10159438 pistons are not forged. My read is that the 10159436, pictured in the section that says they're forged, are the stock diameter version of the 10159438, which is a 30 over piston of the same.
any thoughts / clarifications ? Are these pistons forged as the GM catalog says, or not forged ?
thanks....
Le Mans Master
Joined: Aug 2000
Posts: 8,838
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From: Australia
Note in this GM listing , forged pistons are marked as such.
The LTI/ZZ4 OEM pistons and OS replacements are Hypereutectic (high silicon) pistons
http://www.gmpartsdirect.com/perform...CATID=856.html
The LTI/ZZ4 OEM pistons and OS replacements are Hypereutectic (high silicon) pistons
http://www.gmpartsdirect.com/perform...CATID=856.html
Race Director
Joined: Apr 2003
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From: moraga ca
Hypereutectic pistons are cast aluminum pistons with a higher silica content. As for the strength part, I think you might mean forged aluminum, right? I don't think anyone has made forged steel pistons. Kinda heavy wouldn't you think?
Thread Starter
Pro
Joined: Jan 2009
Posts: 686
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From: Austin Texas
Note in this GM listing , forged pistons are marked as such.
The LTI/ZZ4 OEM pistons and OS replacements are Hypereutectic (high silicon) pistons
http://www.gmpartsdirect.com/perform...CATID=856.html
The LTI/ZZ4 OEM pistons and OS replacements are Hypereutectic (high silicon) pistons
http://www.gmpartsdirect.com/perform...CATID=856.html
Team Owner
Joined: Feb 2006
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From: sw Ohio
I could have sworn that they used to make them, they're all aluminum alloy now. My mistake. I still wouldnt trust a hyper piston in any performance engine.
Thread Starter
Pro
Joined: Jan 2009
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From: Austin Texas
My read is that forged will withstand detonations better, but with the knock sensors and timing retard responsive thereto, isn't damage from detonation a non-issue ?
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Race Director
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From: Slidell Louisiana
I believe that if you're building a stock replacement engine go with the stock replacement hypers. Now if you're going to build a performance engine go for the forged. The stock shortblock is pretty darn stout. However, once you have it apart the money you save using hypers over springing for forged is a fools bargain.
Remember
Powerful, Cheap, Reliable ; pick two!
I have forged pistons in my 355.
Thread Starter
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From: Austin Texas
Not on a high performance engine (you can still have detonation with full spark retard)
I believe that if you're building a stock replacement engine go with the stock replacement hypers. Now if you're going to build a performance engine go for the forged. The stock shortblock is pretty darn stout. However, once you have it apart the money you save using hypers over springing for forged is a fools bargain.
Remember
Powerful, Cheap, Reliable ; pick two!
I have forged pistons in my 355.
I believe that if you're building a stock replacement engine go with the stock replacement hypers. Now if you're going to build a performance engine go for the forged. The stock shortblock is pretty darn stout. However, once you have it apart the money you save using hypers over springing for forged is a fools bargain.
Remember
Powerful, Cheap, Reliable ; pick two!
I have forged pistons in my 355.
Thread Starter
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Joined: Jan 2009
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From: Austin Texas
I'm not disagreeing, but asking out of my own ignorance. When you gonna get that ? I'd be inclined to think one's motor has some serious issues if there were detonation occurring under full retard. I'd not expect detonation under full retard. enlighten me a little ? thanks 
Race Director
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From: moraga ca
The 427 LS7 motor putting out 505 hp has cast hypereutectic pistons. When I was running a 383 I had these pistons with 11:1 compression and was running low 11's for quite a while and never had a problem. Because these pistons don't expand as much as forged pistons, they allow for tighter piston to wall clearance, better sealing and less wear. They are fine for most normally aspirated performance engines.
Thread Starter
Pro
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From: Austin Texas
The 427 LS7 motor putting out 505 hp has cast hypereutectic pistons. When I was running a 383 I had these pistons with 11:1 compression and was running low 11's for quite a while and never had a problem....... Because these pistons don't expand as much as forged pistons, they allow for tighter piston to wall clearance, better sealing and less wear. They are fine for most normally aspirated performance engines.
Le Mans Master
Joined: Feb 2000
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From: Kempner Texas
Some versions require special (wide) piston to wall clearances due to their expansion rate. I believe it's Keith Blacks, but could be others too.
If the specified clearance isn't met, the piston will seize and fail. One engine builder complained about having a barrel full of fail Hyper-Us.
Under normal conditions they're fine. It just becomes an issue when they have to stand up to being really stressed: running lean, detonation, NOS, chargers, etc.
Jake
West Point ROCKS
If the specified clearance isn't met, the piston will seize and fail. One engine builder complained about having a barrel full of fail Hyper-Us.
Under normal conditions they're fine. It just becomes an issue when they have to stand up to being really stressed: running lean, detonation, NOS, chargers, etc.
Jake
West Point ROCKS
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From: Austin Texas
Most definitely. The hypers would melt !!
I haven't messed with the funny gas yet. Where to put the tank in a C4 ???
Would be "cool" if you could run the AC using N2O as a refrigerant gas, then just run lines from the AC reservoir to the intake, on-demand, and re-charge the "AC" as-needed. Dreaming is free.
I haven't messed with the funny gas yet. Where to put the tank in a C4 ???
Would be "cool" if you could run the AC using N2O as a refrigerant gas, then just run lines from the AC reservoir to the intake, on-demand, and re-charge the "AC" as-needed. Dreaming is free.
Race Director
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Some versions require special (wide) piston to wall clearances due to their expansion rate. I believe it's Keith Blacks, but could be others too.
If the specified clearance isn't met, the piston will seize and fail. One engine builder complained about having a barrel full of fail Hyper-Us.
Under normal conditions they're fine. It just becomes an issue when they have to stand up to being really stressed: running lean, detonation, NOS, chargers, etc.
Jake
West Point ROCKS
If the specified clearance isn't met, the piston will seize and fail. One engine builder complained about having a barrel full of fail Hyper-Us.
Under normal conditions they're fine. It just becomes an issue when they have to stand up to being really stressed: running lean, detonation, NOS, chargers, etc.
Jake
West Point ROCKS
Sprayed the snot out of them and ran many 10 second NOS runs until I finally wore out the ring seal. Other than being "slightly" noisy, I liked them.
My projects have always been "value engineered", so I have yet to own a forged piston, and have been quite lucky with cast and hypereutectic's.
Race Director
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Most definitely. The hypers would melt !!
I haven't messed with the funny gas yet. Where to put the tank in a C4 ???
Would be "cool" if you could run the AC using N2O as a refrigerant gas, then just run lines from the AC reservoir to the intake, on-demand, and re-charge the "AC" as-needed. Dreaming is free.
I haven't messed with the funny gas yet. Where to put the tank in a C4 ???
Would be "cool" if you could run the AC using N2O as a refrigerant gas, then just run lines from the AC reservoir to the intake, on-demand, and re-charge the "AC" as-needed. Dreaming is free.
Hyper and cast pistons are harder, and shatter like glass when the fail from detonation.
Lose a cast piston, and you often lose a motor. Lose a forged piston, and you typically lose a piston.
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From: Austin Texas
Thanks for the correction. In that context, forged pistons could be viewed as engine insurance.
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