What the hell are gas ports?
something about holes around the rings or something. What do they do?

 

Gas ports were small holes drilled from the piston top to the inner edge of the top ring land. This applied combustion pressure directly to the top ring to improve sealing. This is a racing thing.

BigBlockk

Later.....

 

gas ports BigBlockk is correct and do not worry about it you do not want them.

 

is it worth the trouble on a street car?

 

If you're chasin' HP you certainly need 'em. We have 'em in the 468" SB we built a few months back (730HP and 650 Torque). Car's driven by customer on daily basis back and forth to work in nice weather only. He ordered "most HP available on 89/93 octane with single 4 brl. carb. He "drives" it on the 89 and "runs" it on 93. No mix whatsover, does have a vacuum pump, and not one issue so far. Been using it for months now. Sits and idles and 800. Thanks, Gary in N.Y.
P.S. The "average all around street unit" dosen't need them however.

 

I am building a turbo motor will it help in the forced induction?

 

Since you did not post a pic of pistons with gas ports , did you actually mean to ask about pistons and designs that use accumulator grooves ?

 

I dont actually know why I posted that picture except that those are the pistons I plan on buying.

Are accumulator grooves and gas ports the same thing?

 

Nope , not exactly but .....

Go to the KB website . The info there will tell you some more about the accumulator grooves and what they do .

KB is not the only piston makers using the accumulator grooves FWIW . JE uses them on certain pistons as well .

 

the piston he posted doesn't have either an accumulator groove or vertical gas ports (an accumulator groove is basically a groove in the 2nd ring land to increase volume there and reduce pressure differential from blowby gas between top and 2nd ring)
Can't see from that angle if it has lateral gas ports but I suspect it has neither.

 

OK so any piston I would buy could have gas ports machined into them.

Thats cool. The speed-pro doesnt come with either. what is the benefit of the accumulator groove? Is there a benefit to the a KB piston versus the speed-pro except for the groove?

 

The accumulator groove is a circumferential groove machined in the ring land between the top and 2nd rings. The purpose of it is to balance the gas pressures above and below the top ring. This helps keep the top ring from lifting off of the bottom of the top ring groove which can cause it to lose it's seal and consume more oil. These are used to prevent "ring flutter" at high RPM's where the inertia forces on the ring are very high. Definitely a good idea for any performance oriented street motor.

The gas ports are an old idea with little merit IMO. Small holes are drilled through the piston tops and into the root of the top ring groove. The idea (in theory) is to direct the combustion pressure to push on the back of the ring to force it against the bore wall and (supposedly) improve ring seal. The truth of the matter is there is plenty of clearance between the top land and cylinder bore for the combustion gases to get behind the ring, forcing it to the bottom of the groove and also into the cylinder wall to seal.
The reality is these ports add nothing to ring seal and at worst weaken the top land by introducing stress risers due to the small holes. If not done correctly, they can even disrupt the ring seal by causing it to lift off the bottom the groove. Dumb idea for a street motor, or a racing motor, for that matter. I'm putting on the flame suit for all the racing "experts" out there who have drilled little holes in the tops of all their pistons.

 

Another thing those pistons won't have after a 1000 miles is that coating on the sides.

SpeedPro makes good pistons but that coating tends to come off. I chose to get the uncoated version when I built my motor after I saw a set of pistons at the machine shop that had the coating worn off and the motor has to be redone

 

I was gonna have them coated by Swaintech in NY. They do some NASCAR truck series engines. how do you get the ones without the coating? Expecially since I want their turbo dish pistons.

 

Don't worry about trying to obtain that piston w/o the skirt coating .

Swaintech only coats the piston skirts with a exact or similar coating and applies the ceramic thermal barrier to the piston top .

Just have the ceramic thermal barrier added if thats your intentions . The other coating comes for free ... more or less .

 

Your right, I am looking for the thermal coating. The skirt coatings arent that much more.....

 

I wouldn't want to use gas ports on any long term motor I would build. They are fine for Drag Racing but no one else uses this technology for engines (they are not seen in Nextel cup, road race or other racing series.) They will "kill" top rings and then the small diameter holes in the piston will fill up with carbon and the ring seal will be much worse than if you had gone with a conventional ring set-up. I would also stay away from thin ring packages on a street/strip type engine.

 

Interesting. Thanks