holes in piston ?

[patgas]

i hav just rebuilt my engine prox piston what advantages of the holes and do i need to put them in ?

[cr5004life]

The holes in the exhaust side of the piston , i would reccomend they help lubricate between the piston and the exhaust bridge. The exhaust bridge is thin and expands alot faster than the the rest of the cylinder especially if your cylnder is ported. as far as putting a whole in the back of the piston, i believe it just lets fuel enter the tranfer ports alot quicker, thus giving u more bottom end, but im not 100% sure on this one

[AlisoBob]

If the bridge is relieved, their is no reason to drill a cast piston like the ProX.