Has anyone ever heard of the term: Ported Pistons.

They are pistons with tiny holes drilled around the outside of the top of the piston.

From my understanding, it is a racing trick to help better ring seal.

How does it do this?

What are the pros and cons of doing this?

Thank you.

 

Ported pistons use combustion pressure to push the rings out tight to the cylinder wall.
The holes go from the top of the piston to the back of the ring.
They're not the best for street because the ports tend to clog with carbon.

 

Agree^^^^^^^ Gas ported pistons aren't recommended for street applications. It does work, but the effect will quickly diminsh as the holes become clogged with carbon.

 

Thanks for the timely replies guys.

So if the ports quickly clog up, that would make it act like a solid piston, correct?

So how does it become a problem?

Has anyone did any testing to see how long a ported piston is good for?

I assume it compresses gases through those small holes and it pushes the air against the backside of the ring?

 

Carbon clogs the holes and they become ineffective. Not something you want when you paid extra for them, plus carbon builds up behind the rings, makes them stick and they actually seal worse than stock. (or solid)
These are really designed for racing engines that get taken apart frequently.
Again:

 

I know Nascar, Pro Stock, Comp. Eliminators, and the World of Outlaws do it. There engines get torn down frequently.

I have read that carbon build-up was not an issue as well. It just depends on how often they are torn down apparantely.

I have read you need proper e-vac and ring tension to run it successfully????

 

I am adding this for my own information:

Another trend has been to drill gas ports in the ring grooves behind the rings. Compression rings typically require .002? to .004? of side clearance so combustion pressure can blow around the ring and force it outward to seal against the cylinder. By drilling tiny gas ports in the back of the ring land, less side clearance is needed and ring sealing is improved. There is also less ring flutter at high rpm, which is where most performance engines spend a large percentage of their running time.

Gas ported pistons work best in high rpm applications and with thin, narrow compression rings. But the high pressure sealing that works well on the race track does not work so well on the street because the added gas pressure also increases ring wear.

 

You might need to get a dry sump oiling system or there is the possibility you could run into oil consumption issues due to lower ring tension. Aviation engines use it too. Thats the reason you can turn a 28 cylinder radial engine over with a 2 foot breaker bar with relative ease. That would be something i would like to do.

 

There are is another type of gas port called lateral gas ports (vs. vertical gas ports). This is what circle track and roadracers use. We drill holes bisecting the top ring groove surface..they won't fill up with carbon, but aren't quite as effective as vertical gas ports. There's also a pressure equalization groove cut into the top of the ring groove that distributes the pressure between the lateral gas ports more equally...it seems to pick up some power as well.

Gas ports force the rings into the cylinderwall a bit harder than normal, so some contend that it hurts ring life, but quite a few people done it on the street and still had good engine life. Some people also think it's something to be done when the rings are thinner than your average 1/16 top ring, but the heavier the ring....the more likely it is to flutter...and the more effective a gas port is.

 

A vaccuum pump is a hell of a lot cheaper than a dry sump and easier to install too.