LT1-LT4 Modifications 1993-97 Gen II Small Block V8

Who can name the weakest part??

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Old Dec 9, 2008 | 09:08 PM
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Default Who can name the weakest part??

Looking for a list in order of the weakest-to-strongest part in the stock LT1 rotating assembly. With mileage being no concern (figure only 15k on the completely original and stock motor if you want), what will be the first thing to go out on our motors? Including everything from the piston skirts to the rings, wrist pins to the bearings. What gives out in the high rpms, and what gives out due to large amounts of spray?

From what I've read, the crank can handle gobs of power, rods are the strongest of the gm motors for its time, and the bearings seem to be able to handle hundreds of thousands of miles. But when someone decides to take that extra step and push a 200 shot through her, or spin her upwards of 6800 what lets go??

Now i understand that most of our motors are high mileage so the bearings tend to be a common issue, but is this due to weakness or just simply due to wear and tear.
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Old Dec 9, 2008 | 09:23 PM
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right now i have a stockbottom end in my car with a 150 shot and i spin it to 7500 i have about 60 passes on it this past season and have not had 1 problem i dont expexct it to make it long next year when i up the spray
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Old Dec 9, 2008 | 09:32 PM
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I think he's talking about an LT1 bro....

you can't spin a stock LT1 to 7500 #1 but i'm assuming from your SN that you own a SOHC mustang...

LT1 will most likely spit the piston first.... you'll bust a ringland or just straight up shatter the piston...

HyperuCRAPtic pistons..... rods and crank will handle a bunch. But detonation will kill the rod and the piston most likely together....
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Old Dec 9, 2008 | 09:41 PM
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I know that detonation can wreak havoc on even the strongest pistons. But assuming your tuning is within reason, there should be no reason for detonation to be a problem. Even with a 300 shot, if your fuel requirements and timing are where they should be, combustion should be fine. Next you are merely looking at component strength. Is the Lt1 piston actually the weak point of the motor?
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Old Dec 9, 2008 | 09:42 PM
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the connecting rods usually go off the crank. the tolerance between the bearings is to much to handle high revs
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Old Dec 9, 2008 | 09:47 PM
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Hypereutectic pistons are a no-no in a high revving, high hp car. They were made to flex
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Old Dec 9, 2008 | 10:02 PM
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I don't care what tune you have in the car.... hyperutectic pistons are brittle and a 300 shot even with a perfect AF ratio will buckle every piston in the car under the extremely high cylinder pressure....

I won't even get started with the fact that a stock rotating assy LT1 with your average ignition system (read opti) could barely generate a strong enough spark to ignite a fuel/air/nitrous mixture on the level of a 300 shot.....

I run as a minimum an HVC II Coil (thanks tony), a digital 7 programmable ignition, a crank trigger and a true rear mount dist.....

but if you did somehow ignite it it would shatter that piston in a heartbeat..... there is a reason why forged pistons setup for large amounts of spray have thick ringlands. Mine have a 300 top ringland.... using a 6" rod in a 383....
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Old Dec 9, 2008 | 10:05 PM
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im talking about my lt1 i have spun it to 7500 since day one trying to break it it has yet to come apart believe me or not i know its true
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Old Dec 9, 2008 | 10:08 PM
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Originally Posted by black46gt
im talking about my lt1 i have spun it to 7500 since day one trying to break it it has yet to come apart believe me or not i know its true
I thought it wasn't safe to take these things any higher than 6300. You're crazy.
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Old Dec 9, 2008 | 10:08 PM
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im talking about my lt1 i have spun it to 7500 since day one trying to break it it has yet to come apart believe me or not i know its true
Okay so let's hear how you somehow got past the fact that the fuel injection tables in the computer only go to 7200..... Anything higher than that the PCM will "DUMB LOCK" thereby hitting an un-erasable rev limiter..... If it has an opti you've never been higher than 7200....

the "BS" Flag has just been raised in my castle....
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Old Dec 9, 2008 | 10:11 PM
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rod bolts or ring lands.

Please give more info on you 7500 rpm stock shortblock. Im sure everyone would like to hear about it.
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Old Dec 9, 2008 | 10:15 PM
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Originally Posted by black46gt
right now i have a stockbottom end in my car with a 150 shot and i spin it to 7500 i have about 60 passes on it this past season and have not had 1 problem i dont expexct it to make it long next year when i up the spray
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Old Dec 9, 2008 | 10:20 PM
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Old Dec 9, 2008 | 10:25 PM
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irc it too...
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Old Dec 9, 2008 | 10:36 PM
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I 2nd the BS flag ! I'm no expert but I'm pretty sure the stock pcm couldn't reach that high of a rpm .
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Old Dec 9, 2008 | 11:06 PM
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I know this is off the topic, but I have a question about the rpm limit of the stock pcm. The main fuel table on my 93 goes to 7000 using Tunerpro RT, but the PE vs. RPM table goes to 7500. Does the pcm shut down at 7200? I don't plan on spinning my motor that high, I just always wondered about this.
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Old Dec 9, 2008 | 11:12 PM
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I find anything past 7K hard to believe on a Stock PCM..
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Old Dec 9, 2008 | 11:25 PM
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I am merely stating what the PE Vs. RPM table rpm goes up to. I figured 7000 rpm in the main table would be the limit, just wondered why my PE table goes to 7500.
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Old Dec 10, 2008 | 06:07 AM
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i can tell you from experience that anything above 6500 is a death sentence for a connecting rod bearing in our motors lol
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Old Dec 10, 2008 | 06:36 AM
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Originally Posted by OutlawZ
I don't care what tune you have in the car.... hyperutectic pistons are brittle and a 300 shot even with a perfect AF ratio will buckle every piston in the car under the extremely high cylinder pressure....

I won't even get started with the fact that a stock rotating assy LT1 with your average ignition system (read opti) could barely generate a strong enough spark to ignite a fuel/air/nitrous mixture on the level of a 300 shot.....

I run as a minimum an HVC II Coil (thanks tony), a digital 7 programmable ignition, a crank trigger and a true rear mount dist.....

but if you did somehow ignite it it would shatter that piston in a heartbeat..... there is a reason why forged pistons setup for large amounts of spray have thick ringlands. Mine have a 300 top ringland.... using a 6" rod in a 383....
All of the above statement is Highly True, as said, cylinder pressure will cause the pistons to crumble like a cracker....
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