im going over it in my head and cant think of any reason why not to, the fixture is set up and when i come back from walking the dogs in a few hours im gonna get started unless someone brings up a consideration ive overlooked between now and then.

anyone had bad experience with gas ported pistons?

 

yeah, its a good idea on a race motor, but a daily driver . it puts more wear on the rings and more pressure on ring lands. not a good idea unless you dont mind inspecting and changing rings fairly periodically. theres reasons there not readily available.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by bluedlude &raquo;</TD></TR><TR><TD CLASS="quote">...it puts more wear on the rings and more pressure on ring lands...</TD></TR></TABLE>

the first part (more ring wear) i will not dispute because i have no data against it.. do you have any in support of it or is that just some reasoning? all rings require cylinder pressure behind them to seal against the bore, their own tension is not enough. during cylinder pressure their bottom face seats on the bottom of the ring groove, during vacuum it shifts to the top.

the second part i have to flat out reject. how can there be additional pressure on the ring lands? the cylinder pressure is the same whether i help it get BEHIND the ring or not. an unported piston will see the exact same downward force on the ringland. the only difference i can imagine now is how much pressure is helping to force the ring outward. im thinking the more the better for the sake of ring to cylinder sealing.

anyone else?

 

After 10k hard miles my gas ported pistons and rings were still near perfect; I see no reason not to try it on OEM pistons.

 

I am pretty sure TBone had gasports on his pistons and when he tore it down (don't know exact numbers--maybe 10,000 miles?) he said they were not plugged up as many claim will happen on a street motor--as far as wear "they" say it increases wear, but I do not know for sure.

 

Its not something that had ever crossed my mind to do to OEM pistons
Regards Dyno Dave

 

now that you mention it, i got to take a pretty close look at tom's IB super dupers when it was apart. i think there was even crosshatch left after some ridiculous amount of abuse/pulls.

 

the only question now is will the pistons structural integrity be weaked by the modification....

 

yes, which is the point DonF mentioned. im contemplating that and all the ringlands ive seen pinched/blown off over the years. they all had taco's rod bearings too which shows how much cylinder pressure a heavy dose of nitrous detonation has to offer. im thinking this motor wont be seeing anything like that. ...hmm.

 

In speaking with some pretty knowledgable engine builders and piston manufacturer reps, they claim that gas ported pistons actually increase ring and piston longevity due the fact that the rings and bore are in constant contact, less flutter.

I think the misconception of them being a race only peice comes from the fact that so many members are severly stressed on a race engine. It could have all started after someone with the gas ports tore his engine down to see cracked lands, and blamed it on the gas ports. Maybe they would have cracked anyway. It was a race motor, right?

I think when a piston is designed with gas porting in mind, its structural integrity shouldnt be an issue, modding a set of OEM's is hit or miss.

 

I almost bought gas ported rollerwaves once for my motor from Larry Widmer of ENDYN. He talked me out of it, He said it would increase wear on the rings and would only be a good idea, if I planned on rebuilding the motor once a year.

 

i just sawed a cast piston in half. im definately doing it now. ill update some other time.

 

i ended up converting them to forced pin oiling since the squirters have been deleted. also machined a bunch of other tricks in there and set back up to do the gas ports tomorrow when i get up. im going with 8 holes at .032" diameter. still have to move the exhaust reliefs back a hair since i milled the quench pads off a b16 head, which took about .090" and reduced the radial clearance on the exh margins. intakes just barely squeek by.

anyways. about cylinder wear and gas ports, im really starting to expect less ring/cylinder wear with the porting done. the ring grooves have such a tiny little bit of clearance for cylinder pressure to seep by that i cant imagine much of it really getting behind the ring to expand it. if it isnt pressed against the cylinder wall i envision it doing a lot more fluttering and rocking (so that the upper and lower sharp corners of the ring are biting into the cylinder wall.) with cylinder pressure always instantly behind the ring and in an even fashion, i think the ring will be prone to remain much more square against the bore. if so, the crosshatch would last a lot longer i think.

when the cylinder sees vaccuum i suppose the rings will want to collapse? which could be good for power but bad for blowby?

 

what block are you doing this to? id love to see some pictures

 

this particular engine is a gsr bottom end with itr rods/pistons and a b16 head milled till it looked like a gsr.

 

I've had good luck with lateral gas ports.These appear as eight or so half circles above the top ring.They are nearly unaffected by carbon buildup.The piston companies claim it is just as effective as vertical gas porting.You can see them on JE's website.They are standard on some small block Chevy pistons as an example.They can do it as an option on almost any piston.

 

hey thanks for the tip,, i suppose those are significantly more shielded from combustion crapola loading up in them. and theyd be easier to do if i can find an end mill that tiny..

decisions decisions.

 

What cams are you going to run in this combo? Are you having to take alot out of the valve reliefs to compensate for the amount taken off the head?

 

hey rico, the stock intake actually is acceptable for radial clearance. its only running ITR cams now, maybe bc3+ or some other moderate cam later. exhaust needs to shift back about .030" only because of the fillet/radius in the casting. if it were a forged piston with a square machined relief it would fit, no matter how far i had the cams in either direction, i was surprised actually.

i just vertical ported a pr4 piston with about 8 .040" holes bunched together on one side and hammered the snot out of the whole compression height edge. i couldnt break off the top corner and the ring still slides freely all the way around the piston. that pretty much answers my questions.

couldnt find an end mill small/rigid enough to do the lateral ports or i would.

 

Props for trying something different.

 

thanks man.. still have the same goal as everyone else though

 

nobody in here has subscribed to the theory that the gas ports release the tension on the ring as it glides down the bore due to the pressure differentials??
reducing the frictional HP figure

 

Ok I read this the other night, realized I didn't know a whole lot about gas porting, tried to read up on it as much as I could, and came up with a question or 2. excuse me if I sound like a moron, but here goes, just trying to learn.......

I can picture vertical ports no problem, but I'm having some trouble either finding pics of or visualizing in my mind exactly what a horizontal port looks like

From what I have read, gas porting lets you run a tighter ring side clearance. this helps reduce the "fluttering" of the ring. if you run a stock piston with a stock ring groove, will you run a thicker than stock ring to end up with a smaller side clearance?this seems to be one of the big advantages of doing it, so just running a stock piston you have gas ported, with a stock ring seems to be missing out on one of the big advantages.

 

Bump for the creative thinking.
Show pics of the piston and combustion chamber if you can.
What headgasket are you using and what compression ratio are you aiming for?

 

I say cheers for Mike for making it up there with the big guys. He still has a way to go, but his hard work has definately paid off. Lesson to all HT'ers, be like Mike. Use your ears (and eyes) more than your mouth (and fingers)