When is gas porting needed

[DCarr511]

I'm curious as to when it becomes benificial to have the pistons gas ported ?

I have a 4.375 bore BBC going together and was considering it.

Is enough metal removed to require a rebalance ?

[0260IN3]

Mostly gas porting is benificial when you start to get an engine with a large bore or high RPM. Being that you are at 4.375 it will most likley help your engine. Three other things you need to consider to get the full benifit of gas porting are:
1. Lighter tension rings. The gas porting pushes the ring out on compression stroke, but on the other 3 strokes you don't want the ring to drag more than it has to.

2. Check the fit of your ring in the ring land. If it is very loose the gas porting will provide less benifit becasue the pressure created by the gas porting will be lost.

3. A vacuum pump is also a good idea with gas porting because it helps relieve the pressure on the bottom side of the piston on all 4 strokes of the engine and also helps if you have a very light tension ring package so the engine won't smoke. (and also is great to help stop oil leaks)

Hope this helps some

[0260IN3]

There should be no need to rebalance. Minimal weight is removed when you gas port.