Hi guys...

I just bought a set of hi comp pitons for my bigport build.
There are exactly the same as small port pistons but with the right sized 18mm pin bore..

Being the curious person I am... And having a disasembeled small port in my garage is thought I'd compare the too to see just how similiar they really are..

Weeeeellll...
Visually there identical untill I noticed that the pin heights are different...

Small port pin height measured form top of piston to center of gudgeon
= 30.25mm

The new pistons I bought only = 27.6mm

Fitting these piston would lower my compression ratio a whole 2.3 points.
From a ( If they were right ) 10.32 down to only 8.06

Any ideas.???? I'm unaware of any rod or block deck hieght differences between models.. Why is this so.??
These look just like genuine 4a pistons... With the ART stamp on the side and all..