Strange slits cut into lower side skirts of Pistons????

[Curt Curtiss]

We finally got to pulling the engine out of the 1933 8-105 and when we removed the pistons we were surprised. I found each of the pistons we labeled .060 over so that was ok.

 

The strange part is they had a hole drilled in the skirt along with a "T" style slit in the sides of Pistons below the ring level. I have never seen this before, have you all seen this and what would the reason be for doing this?

[Owen_Dyneto]

An expansion slot to control skirt expansion, an extremely common feature found on the vast majority of pistons.

Edited December 25, 2017 by Owen_Dyneto (see edit history)

[Ben Bruce aka First Born]

18 minutes ago, Owen_Dyneto said:

An expansion slot to control skirt expansion, an extremely common feature found on the vast majority of pistons.

 

 Right on, Owen.

 

  Ben

[Rusty_OToole]

Aluminum pistons expand with heat, a lot more than the water cooled iron cylinder. To avoid the piston seizing in the bore they would have to leave so much clearance when cold, that piston slap would be a problem. Instead they used various methods to allow for expansion like making the piston oval and cutting  a T slot in the skirt. Other solutions included wrapping the piston in piano wire and casting in a steel strut.

[Curt Curtiss]

4 minutes ago, Rusty_OToole said:

Aluminum pistons expand with heat, a lot more than the water cooled iron cylinder. To avoid the piston seizing in the bore they would have to leave so much clearance when cold, that piston slap would be a problem. Instead they used various methods to allow for expansion like making the piston oval and cutting  a T slot in the skirt. Other solutions included wrapping the piston in piano wire and casting in a steel strut.

 

Very good to know, thanks!