Gas porting pistons

[Quick_2s]

What is it and what purpose does this serve, just curious.

[hi$toy]

we gas ported all our Drag Racing Motors ---you have small holes drilled into the edges at the ring glands, this promotes better seal on the engines at high RPM-but you have to re ring after 250 runs or so-would not suggest for a street motor...unless you like rebuilding every 150 miles

[Quick_2s]

Makes sense, so the extra pressure on the rings wears them faster? I saw it offered by the shop that did my heads and flywheel, now I know what it is for.

[uglyDougly]

  Grumpy Jenkins (the Pennsylvania Pygmy) was one of the first to do that. Acceleration or rather de-acceleration of the pistons approaching TDC causes normally clearanced rings to lift off the bottom of the ring land. Since the only way cylinder pressure gets behind the rings (normally) is around the pistons and above the top ring, if the ring moves up it shuts off the pressure source.
  Flutter can be lessened by decreasing the clearance in the ring land but as you approach zero up-down, the gas can't get behind the ring. Thus the ports.

   Way back in the good-old-days Steve Ferree gas ported a Triumph he was building for hill-climbing and he found that the ports soon plug up. That's why his$toy mentioned the service interval of 150 miles.

  The ports don't wear the rings out, done right the rings see normal pressure. But zero clearance can save rings and grooves, ring flutter absolutely knackers the ring grooves, then it's piston time.

   Doug