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Generation III Internal Engine
1997-2006 LS1 | LS6
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Old 06-05-2005, 08:15 PM   #1
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Default Cast vs. Forged Piston weight.

Are forged 347 pistons heavier than stock cast. If so, can I remove enough material from the forged piston to make them the same weight as cast pistons with out having to rebalance crank. Motor will be used with at least 200hp shot of direct port nitrous.
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Old 06-05-2005, 09:34 PM   #2
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They are probably lighter. Most forged piston are high performance pistons, which in most cases is a lightweight piston. The cast pistons like stock and aftermarket stock replacement are usually not lightweight. I dont think the forging process adds weight if it heat treating. If its forging done by basicly pounding the metal to make it more dense then I an see it being a little more mass because it will be compressed. But then again I would bet that it would be machined to lighten it back up.
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Old 06-06-2005, 01:09 AM   #3
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umm you will want to have it balanced regardless trust me...
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Old 06-06-2005, 03:00 AM   #4
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Forged should be heavier because of the denser metal.
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Old 06-06-2005, 11:38 AM   #5
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I did a search. OEM MAHLE cast LS1 piston weighs 434 grams. All the forged pistons I found are lighter than the OEM cast piston. So far the JE forged piston part # 194884 is the closest to OEM weight, but is still lighter @430 grams. The new Ross forging part #99838 is claimed to be designed for nitrous use, but Ross did not list the weight on their web site.
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Old 06-06-2005, 01:18 PM   #6
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Quote:
Originally Posted by LS1_PNYTAMR
umm you will want to have it balanced regardless trust me...


Yes you will need to balance this regardless of what aftermarket pistons you use.
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Old 06-06-2005, 06:24 PM   #7
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Quote:
Originally Posted by JZ'sTA
Yes you will need to balance this regardless of what aftermarket pistons you use.
If I replace my cast pistons and pins with forged pistons and pins of exact same weight and using OEM rings that are .005 oversize." WHY " would I need to rebalance crank?

Someone does not understand how a crank is balanced.
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Old 06-06-2005, 07:14 PM   #8
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Ok,
You wouldnt "NEED" to balance it. Look at it this way, you are required to have car insurance, but you do not "HAVE" to have it. However if you get into a wreck and dont your "SOL"

Same basic princepal, you need to have the motor balanced, if you dont, it will still run, hell if you get pistons that are lighter, the motor will still run, just not as well.

Take a further look at what your trying to do, if you want to run at least a 200 shot, you should prolly look into doing more than just pistons. That is alot of nitrous, and for longetivitys sake I would say build it right, build it once.

ITS CHEAPER TO DO IT ONCE RIGHT, THAT TWICE WRONG, TWO LEADS TO THREE, AFTER THREE IF YOU DONT DO IT RIGHT, YOUR MACHINE SHOP IS STEALING FROM YOU.
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Old 06-06-2005, 08:15 PM   #9
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I once rebuilt an engine (455 Pontiac) USING A DIFFERENT WEIGHT PISTON. The motor was way out of balance and you could feel the engine vibrate badly while seated in the car. The motor eventually spun a rod bearing. I rebuilt the motor a second time, this time balancing the total assembly and rebuilding the big end of the rods on the tight side for more bearing crush. END OF PROBLEM.
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Old 06-06-2005, 08:56 PM   #10
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Quote:
Originally Posted by gollum
I once rebuilt an engine (455 Pontiac) USING A DIFFERENT WEIGHT PISTON. The motor was way out of balance and you could feel the engine vibrate badly while seated in the car. The motor eventually spun a rod bearing. I rebuilt the motor a second time, this time balancing the total assembly and rebuilding the big end of the rods on the tight side for more bearing crush. END OF PROBLEM.
you answered your own question
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Old 06-06-2005, 09:55 PM   #11
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So wait, youve already had a problem with a out of balance motor, and now your trying to do the same. Or are you trying to say youve learned from your mistake and would rather find a piston that is exactly the same.

Have you looked at Mahle pistons?
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Old 06-06-2005, 10:14 PM   #12
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I am saying if you use the same weight piston when rebuilding LS1 you do not need rebalancing if RPM's are kept below 6500 IMO. I am also saying that I know what an out of balance motor feels like.
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Old 06-06-2005, 10:21 PM   #13
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Quote:
Originally Posted by stang killer
you answered your own question
My original question was, are forged 347 pistons heavier than stock?

Never mind everybody.
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Old 06-07-2005, 10:04 PM   #14
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listen to me please ... i seriously doubt it will be heavier as forged pistons are mostly hi performance pistons and a big part of being hi perofrmance is lightweight .... they are lighter
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Old 06-08-2005, 02:02 PM   #15
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all aluminum forged are lighter than cast.
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Old 06-08-2005, 03:14 PM   #16
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Quote:
Originally Posted by slowpoke96z28
all aluminum forged are lighter than cast.
Ditto

Also spend the 200-300 bucks on balancing. It is worth it.
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