what compression are these pistons

[cruisintalonawd]

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[toofast82]

A quick search of manufacturer and part# came up with 8.5:1 compression
https://www.horsepowerparts.com/index.php?content_id=175&product_id=694

I hate when my SEARCH button doesnt work

 

[cruisintalonawd]

i searched the number and couldnt find anything. why is the Comp height the same as 9.0:1 piston then?

 

[delta448]

According to my math, they're 8.3:1 installed at zero deck.
Head gasket thickness, any material removed during resurfacing and volume between the piston and deck would need added/subtracted in. That's assuming a head with combustion chambers which are 47cc in volume also.

Anyone else come up with that?

i searched the number and couldnt find anything. why is the Comp height the same as 9.0:1 piston then?

The compression height usually isn't changed unless rod or stroke changes make it necessary. It's easier for a piston to be made with a different dome volume.


Edit: I double checked and my math was wrong, I forgot to add in the slight displacement increase of the overbore.
I believe they are indeed 8.5:1 CR as noted.

 

[cruisintalonawd]

I think I had .005 taken off the head but I'm sure that wouldn't raise it very much.
thank you though

 

[SonySlave]

A quick google search of the MIT367366I13 part number came up with 8.5:1 compression ratio.

 

[MidShipCivic]

The compression applies to the cylinder head it's used with you will have higher compression with a 2g cylinder head, because it has less combustion chamber CC's