Piston orientation (arrow)

[ChuckZZ]

Is there an advantage one way or the other? Back in the day I have tried it both ways, if there is and advantage, I do not recall. Building a flatty for the first time in years.

 

[Flatlives]

Aarow always points to the flywheel side.

 

[flattop1]

there is a slight rod angle difference .
Due too piston pin offset .
With stock briggs pistons.

 

[CarlsonMotorsports]

From the factory, the arrow points toward the flywheel side.
If you reverse the piston, you take advantage of a slight offset in the wrist pin location and you get some more dwell time @ TDC.


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Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
33 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com

 

[ChuckZZ]

From the factory, the arrow points toward the flywheel side.
If you reverse the piston, you take advantage of a slight offset in the wrist pin location and you get some more dwell time @ TDC.


-----
Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
33 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com

Thanks for your responce. I thought it was some thing like that. Is there a downside to installing toward PTO side? Like additional piston scuffing?

 

[CarlsonMotorsports]

There was a trend for years to reverse the piston in stockers then that has gone away to some extent. Partly because of sleeving, offset boring, and slant boring, etc.
With the rod angle we've got in the stock class dictated by the stock length rod and pin height, you're going to get piston scuffing on the thrust side regardless of the tiny amount of offset in the wrist pin boss. Builders today don't seem as concerned with the direction -- maybe they just don't care as much about the flathead as they used to.