New piston weight difference matter ?
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From: Maryland i
New piston weight difference matter ?
I have a 72 shovelhead that was stroked along time ago with an old s&s kit . The barells were already .060 over so I got some new ones and I bought s&s pistons that were .020 over to give the machinist something to work with. Just for giggles I weighed them on a scale including the wrist pins, keepers , and ring pack . It turns out the whole setup is 50 grams lighter than my old setup which used s&s trw2800 pistons that no longer exist as a replacement. Originally I asked s&s if the weight difference was a problem and they said no it will be fine . I meen they should know what they are talking about but is that too much weight difference ? The rest of my motor is great so I really dont want to rip it down ..
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From: la la land jerzey
It’s 100 grams of respirating weight as you weigh both and pins and rings and the 1/2 connecting rod weight of both rods in a balance arena for the factor
it was originally set at 60 percent balance factor , that is S&S number they came up with for equal weight flywheels that are the same thickness
the engine is always off balance because the rear rod is much heavier then the front rod — look in the engine block you will see on the crank pin the difference between them — having said all of that - lighter weight pistons in that stroker should help at 3000 rpms as that is the split in the balance - in no way can one give you a real answer as to it will for sure work — but its the lighter piston is going that way at a guess i would say you could end up in the hi 50s in balance and that is what we have found is smooth for all around riding — but again its a guess as you dont have the original balances numbers to confirm what’s going to happen
try it you have nothing to loose - if your hands go to sleep then pull the engine and have at it
it was originally set at 60 percent balance factor , that is S&S number they came up with for equal weight flywheels that are the same thickness
the engine is always off balance because the rear rod is much heavier then the front rod — look in the engine block you will see on the crank pin the difference between them — having said all of that - lighter weight pistons in that stroker should help at 3000 rpms as that is the split in the balance - in no way can one give you a real answer as to it will for sure work — but its the lighter piston is going that way at a guess i would say you could end up in the hi 50s in balance and that is what we have found is smooth for all around riding — but again its a guess as you dont have the original balances numbers to confirm what’s going to happen
try it you have nothing to loose - if your hands go to sleep then pull the engine and have at it
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Joined: Nov 2024
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From: Maryland i
It’s 100 grams of respirating weight as you weigh both and pins and rings and the 1/2 connecting rod weight of both rods in a balance arena for the factor
it was originally set at 60 percent balance factor , that is S&S number they came up with for equal weight flywheels that are the same thickness
the engine is always off balance because the rear rod is much heavier then the front rod — look in the engine block you will see on the crank pin the difference between them — having said all of that - lighter weight pistons in that stroker should help at 3000 rpms as that is the split in the balance - in no way can one give you a real answer as to it will for sure work — but its the lighter piston is going that way at a guess i would say you could end up in the hi 50s in balance and that is what we have found is smooth for all around riding — but again its a guess as you dont have the original balances numbers to confirm what’s going to happen
try it you have nothing to loose - if your hands go to sleep then pull the engine and have at it
it was originally set at 60 percent balance factor , that is S&S number they came up with for equal weight flywheels that are the same thickness
the engine is always off balance because the rear rod is much heavier then the front rod — look in the engine block you will see on the crank pin the difference between them — having said all of that - lighter weight pistons in that stroker should help at 3000 rpms as that is the split in the balance - in no way can one give you a real answer as to it will for sure work — but its the lighter piston is going that way at a guess i would say you could end up in the hi 50s in balance and that is what we have found is smooth for all around riding — but again its a guess as you dont have the original balances numbers to confirm what’s going to happen
try it you have nothing to loose - if your hands go to sleep then pull the engine and have at it
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Joined: Jul 2014
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From: Cental, MI
May be surprising but...Many Folks move away from 60% on Purpose...for Various Reasons..I agree with "Try it"
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Feb 15, 2013 02:17 PM