Either should work fine from the standpoint of gas flow. Sideways (removing semi-circles of material from the top flank of the top groove) seems less likely to result in structural problems.- InHiding
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i agree with InHiding
i've used pisons with gasports either way successfully
the only 2 things about the vertical gasports are
1-easier to do
2-makes piston more prone to possible ring land failure if into localized detonation in some engines depending on
how far top ring is down and ring land thickness
usually, the intake notch pad closest to piston deck, is where detonation will 1st likely to occur. Too many top gasport holes in this location, along with thin ring land due to high ring placement ..and cracks or failure occurs in this area (intake-notch -to- deck pad)
the horizontal or side gas ports help keep ring land stronger/intact than vertical gasports
also gasports are hidden from view <Rules cheating

>
but i still drill my pistons with vertical gasports
in my fixture, i normally just use (8) .050" holes , instead of drilling 12 or so smaller holes like i've seen others do
Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
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