LS1 5.7 Crank
12-31-2010, 09:14 PM
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LS1 5.7 Crank Hi Guys,
Im new to LS engines, just wondering about how much rpm the factory 5.7 3.622 cranks will safely see, will be using Ali rods and planing on turning 8500 to 9000.
Have had some people tell me to keep factory crank to 8000 or less
Im new to LS engines, just wondering about how much rpm the factory 5.7 3.622 cranks will safely see, will be using Ali rods and planing on turning 8500 to 9000.
Have had some people tell me to keep factory crank to 8000 or less
12-31-2010, 10:07 PM
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How long are you planning on using that stock crank at 9K? less than 5 min? It would probably live that long and it would be extremely entertaining if it didn't.
A top fuel engine is completely rebuilt with far less than 5 min run time between builds.
What's your application? Often by the time aluminum rods are being used lightweight forged crankshafts are also being applied to take advantage of the light rods.
Either way engine balancing gets far more important at those speeds.
I have to agree. Good parts only. Awesome assembly work required as well!
If you want reliability at high rpm both perfection and luck are required.
A top fuel engine is completely rebuilt with far less than 5 min run time between builds.
What's your application? Often by the time aluminum rods are being used lightweight forged crankshafts are also being applied to take advantage of the light rods.
Either way engine balancing gets far more important at those speeds.
I have to agree. Good parts only. Awesome assembly work required as well!
If you want reliability at high rpm both perfection and luck are required.
01-01-2011, 03:32 AM
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Thanks for the replys guys,
Interesting I thought the factory LS cranks could handle pretty good power and reasonable rpm, and would have at least been similar to Gen 1 SBC factory stuff
Over the years I have seen quite a few factory SBC cranks both steel and cast handle 8500/9000 in Drag Race only engines with Ali rods, the Ali rods are much easier on the crank.
This was often all guys used years back when the cost of aftermarket cranks were out of most peoples budget
Interesting I thought the factory LS cranks could handle pretty good power and reasonable rpm, and would have at least been similar to Gen 1 SBC factory stuff
Over the years I have seen quite a few factory SBC cranks both steel and cast handle 8500/9000 in Drag Race only engines with Ali rods, the Ali rods are much easier on the crank.
This was often all guys used years back when the cost of aftermarket cranks were out of most peoples budget
01-01-2011, 07:33 AM
#7
I don't see why a properly balanced ls1 crank wouldn't take that rpm. heck even stock balance variation it should. now rods, pistons and the oiling system is what would concern me on the bottom end.
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01-01-2011, 08:18 AM
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Better advise would be to drop TSP an e-mail and get their opinions.
I bet they will know exactly what the limitations of the stock crank are.
Anything can be made to run high rpm. How long it will live is the harder question to answer.
Inertial loads are porportional to the engine RPM squared. I believe a 9000 rpm engine has more inertial loading on the crank then that same engine run at 6000 rpm with 15 lbs of boost on it.
If I HAD to use the stock crank at that speed (due to rules of class or some such nonsense) I'd want it crack tested, shot peened, machined with HUGE radiuses, lightened-balanced for my light rotating assembly, and nitrided/heat treated.
The cost of such preparation will get close to or excede the price of a forging and the good forgings will already have the above done.
I'd e-mail TSP for their take on this.
Their "banner" states they have the fastest stock block LS1 in the country. They are using the stock crank in a sub 10 car. I wonder if the've done a bunch of "prep" to it.
I bet they will know exactly what the limitations of the stock crank are.
Anything can be made to run high rpm. How long it will live is the harder question to answer.
Inertial loads are porportional to the engine RPM squared. I believe a 9000 rpm engine has more inertial loading on the crank then that same engine run at 6000 rpm with 15 lbs of boost on it.
If I HAD to use the stock crank at that speed (due to rules of class or some such nonsense) I'd want it crack tested, shot peened, machined with HUGE radiuses, lightened-balanced for my light rotating assembly, and nitrided/heat treated.
The cost of such preparation will get close to or excede the price of a forging and the good forgings will already have the above done.
I'd e-mail TSP for their take on this.
Their "banner" states they have the fastest stock block LS1 in the country. They are using the stock crank in a sub 10 car. I wonder if the've done a bunch of "prep" to it.
