Difference between pistons?
- Thread starter Airborne
- Start date
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pjtoledo
'ol man in the SHO
I recall checking the pistons a few years ago, no offset. I also recall a magazine article about offset and it mentioned that some blocks had the offset cast into the bores. probably C & D, or R & T. I don't know if our bores are offset from the crank centerline.
This might help, if you go the bottom of this link, you can download the SHO engine book, on page 83 it talks about left and right pistons
https://www.dropbox.com/sh/77a1h1wsvvdmtox/AACBSbusdJqRt-PIONbmMpeTa?dl=0
https://www.dropbox.com/sh/77a1h1wsvvdmtox/AACBSbusdJqRt-PIONbmMpeTa?dl=0
Last edited:
Thanks, guys!
Last night I measured both Left and Right piston every way I could think of. The only difference I found was the piston pin bore on the Right piston is offset .020" towards the exhaust side. The Left piston pin bore is centered between the skirts.
From SHO NUT's site:
Notes on offset:
Wiseco pistons use offset piston pin holes, just like OEM. This makes for a quieter piston. Thus you will receive 3 left bank pistons and 3 right bank pistons. Simply matching the valve reliefs is not enough for correct installation – you need to make sure the piston offset is correct for the orientation
Anyone see an issue with running Left pistons in all bores? Little more noise? There are millions of motors out there running centered piston pin bores on Right and Left bank of a "V" motor.
Last night I measured both Left and Right piston every way I could think of. The only difference I found was the piston pin bore on the Right piston is offset .020" towards the exhaust side. The Left piston pin bore is centered between the skirts.
From SHO NUT's site:
Notes on offset:
Wiseco pistons use offset piston pin holes, just like OEM. This makes for a quieter piston. Thus you will receive 3 left bank pistons and 3 right bank pistons. Simply matching the valve reliefs is not enough for correct installation – you need to make sure the piston offset is correct for the orientation
Anyone see an issue with running Left pistons in all bores? Little more noise? There are millions of motors out there running centered piston pin bores on Right and Left bank of a "V" motor.
pjtoledo
'ol man in the SHO
interesting, the right side is offset and the left isn't. what year pistons? 3.0 or 3.2?
3.2
Yeah, doesnt sound right.
After researching piston pin offsets, I learned, if offset is placed, it is placed against the rotation, for better wear and quieter pistons.
So, the Left pistons should have a offset towards the intake. I am going to double check my measurements tonight. If anyone else has some laying on the shelf and can verify measurements, that would help.
Yeah, doesnt sound right.
After researching piston pin offsets, I learned, if offset is placed, it is placed against the rotation, for better wear and quieter pistons.
So, the Left pistons should have a offset towards the intake. I am going to double check my measurements tonight. If anyone else has some laying on the shelf and can verify measurements, that would help.
I conducted a little bit more google searching.
Some engine builders report different offsets in Left bank and Right bank pistons that have come out of Porsches and VWs. And those engine builders do not know why and don't know how find someone that would know why. There might be some more manufacturers out there that do this, but most people don't measure the piston bore offset when disassembling a motor. These builders have built them all different ways. Some with zero offset, some like they were disassembled with zero offset on one bank and 0.020" on the other bank, some with 0.020" offset both banks with little discernible difference. Some have even installed the pistons with 0.020" in the opposite direction for a couple more horsepower with a trade off that their motors sounded like "cement mixers".
As pjtoledo stated, some manufacturers offset the cylinder bore in relation to the crank centerline to gain offset, however this is mostly done to save in parts cost by being able to cast and stock one piston instead of two. So, in our V6 motors, that advantage would be mute unless there is some other reason Yamaha offset bored the left bank of cylinders and offset the piston pin in the right bank. I wonder if Wiseco, when they make those pistons for SHO NUT, use the OEM offset or 0.020" for both banks? I will email Josh and see if he knows.
Some engine builders report different offsets in Left bank and Right bank pistons that have come out of Porsches and VWs. And those engine builders do not know why and don't know how find someone that would know why. There might be some more manufacturers out there that do this, but most people don't measure the piston bore offset when disassembling a motor. These builders have built them all different ways. Some with zero offset, some like they were disassembled with zero offset on one bank and 0.020" on the other bank, some with 0.020" offset both banks with little discernible difference. Some have even installed the pistons with 0.020" in the opposite direction for a couple more horsepower with a trade off that their motors sounded like "cement mixers".
As pjtoledo stated, some manufacturers offset the cylinder bore in relation to the crank centerline to gain offset, however this is mostly done to save in parts cost by being able to cast and stock one piston instead of two. So, in our V6 motors, that advantage would be mute unless there is some other reason Yamaha offset bored the left bank of cylinders and offset the piston pin in the right bank. I wonder if Wiseco, when they make those pistons for SHO NUT, use the OEM offset or 0.020" for both banks? I will email Josh and see if he knows.
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