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 Post subject: Gas Porting Pistons?
 Post Posted: Sat Feb 05, 2011 12:25 pm 
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OK so I'm probably going to do this to my pistons while the engine is down and I've got a couple of questions.

How many gas ports are needed on a 4.155 bore with an .062 ring? I've heard 7 to 9 so what is the determining factor on this?

Been mentioned that I'll need a low tension ring along with the gas porting so which ring would you recommend for this?

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 Post subject: Re: Gas Porting Pistons?
 Post Posted: Sat Feb 05, 2011 8:26 pm 
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The Ross pistons I ran in the 18º were .043"/.043"/3/16" had 8 holes #52 drill (.0635"). I had Ross do the gas-porting when I bought the pistons, that's how they did it. I thought 8 holes wasn't enough and most you see have more than that ... between 10 - 13 holes.

I think most of the total reduction in ring drag comes from the thinner rings - (horiz and radially) in the compression rings and I haven't seen any compression rings for 1/16" advertised as such. There are low-tension oil rings advertised and when you see a set advertised as low tension on most any parts site it is only the oil ring that is low tension.

I am working on a friends 355 to 383 upgrade that has pistons with 1/16" - 1/16" - 3/16" rings and have begun scouting the ring options as I am planning to gas-port these pistons too and was thinking less tension. Will probably call and talk to someone at one or more ring mfgs to figure out the ring(s) I want and are in the owners budget. Even the normal low tension oil rings you can buy are no problem for anything I've run them in. I think they make lower tension oil rings than the normally advertised stuff. Also Planning on the Napier 2nd rings to help with oil control along with the low tension oil rings.

Rick


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 Post subject: Re: Gas Porting Pistons?
 Post Posted: Sun Feb 06, 2011 1:58 am 
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Ken,

I usually space the gas ports about 1.375 apart. Pay attention to the valve pockets. I try to stay away from the deeper parts of the valve pockets. It would be nice if all the gas ports were evenly spaced, but it isn't as critical as you may think. I'll usually measure from valve pocket around to the other one and make them as even as possible. Then measure the other side of the pockets and make them as evenly as possible.

http://www.goodson.com/technical_suppor ... %20078.pdf

The picture in this pdf gives a pretty good idea of what I mean. Let me know if you have any questions

Don

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 Post subject: Re: Gas Porting Pistons?
 Post Posted: Sun Feb 06, 2011 9:53 am 
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Don I can deal with the machining aspect of this, ie, around the valve reliefs but haven't seen anything listed on low tension .062 compression rings? Who makes these? And that dimension between the holes helps too, thanks. ;-)

I put "low tension" rings in it when I built it but like Rick noted, that's a low tension oil ring, not a compression ring? And I'm going to run those oil rings again too BTW. They weren't a problem before so they'll get used again. In fact, only half the taper face is gone on the second ring? Haven't checked end gap yet as the block is still at the machine shop but will be interesting to see what that is after 300+ passes.

Hopefully we'll have a little more info if Rick calls some "ring" ppl and posts that info here.

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 Post subject: Re: Gas Porting Pistons?
 Post Posted: Sun Feb 06, 2011 1:09 pm 
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Call total seal, they should be able to give you some good guidance. I would think that any of the major ring manufacturers could help you out with this. You'll see a huge difference in drag when you get a good set of light tension rings in there. Just rotating the assembly over while assembling the short block you can note a huge decrease in drag created from the rings. Especially if you have put a lot of engines together.

Don

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 Post subject: Re: Gas Porting Pistons?
 Post Posted: Sun Feb 06, 2011 1:27 pm 
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Some info floating around on ST on gas porting here.
http://speedtalk.com/forum/viewtopic.php?f=1&t=25312


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 Post subject: Re: Gas Porting Pistons?
 Post Posted: Sun Feb 06, 2011 5:31 pm 
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jmarkaudio wrote:
Some info floating around on ST on gas porting here.
http://speedtalk.com/forum/viewtopic.php?f=1&t=25312


Here is another thread that was going on over on ST also.

http://speedtalk.com/forum/viewtopic.ph ... 62&start=0

Something on the Dart Board also.

http://www.dartheads.com/dartboard/show ... php?t=2355

Don

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 Post subject: Re: Gas Porting Pistons?
 Post Posted: Sun Feb 06, 2011 6:45 pm 
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OK so why not post some of that info here instead of sending our members to another board???? ](*,) [-( While I don't have a problem with other boards, I do have a problem when it comes to redirecting people somewhere else.

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 Post subject: Re: Gas Porting Pistons?
 Post Posted: Sun Feb 06, 2011 8:37 pm 
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An engine builder told me the other day that some others are using fewer and fewer gas ports.


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 Post subject: Re: Gas Porting Pistons?
 Post Posted: Sun Feb 06, 2011 8:46 pm 
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Ahhh you are correct,....but remember. They had to be here first to be directed there. Besides, I'm sure that information will come this way as any here will end up there. You and I have already talked about this in the past.

Don

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 Post subject: Re: Gas Porting Pistons?
 Post Posted: Mon Feb 07, 2011 6:53 pm 
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I posted this on another site so I thought I would post it here also.


Adger Smith wrote:"per Adger's terse comment"
I've gone to lateral gas ports on my latest NOS engines.



20 years ago, or so, a Speed Shop that I learned most of how I do things prepared 2 identical sets of pistons for one of their Dodge prostock engines. One set was gas ported vertically and one set was laterally. Did back to back dyno testing and ran both sets of pistons at the track, in competition, and found that they both performed the same. Laterals were pretty much self cleaning and didn't plug up. Plus you didn't have to worry about broken drill bits ending up in the tops of your pistons while you were machining in the gas ports. They did all their work on a mill with a rotary table. This is a big reason I don't even consider using the vertical gas ports in anything I build. I have also seen where the verticals tend to weaken the ring lands in around the valve reliefs, where the laterals don't.

The speed shop mentioned here was the Wayne County Speed Shop in case you are wondering. Those guys were damn good at what they did, and still are.

Don

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 Post subject: Re: Gas Porting Pistons?
 Post Posted: Tue Feb 08, 2011 12:36 pm 
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Just got off the phone w/Total Seal.

They don't recommend gas-porting a 1/16" ring piston. The top ring has more than enough tension to seal and will only increase ring drag and wear out the ring faster. The .043" rings with the reduced radial thickness will have significantly less drag and need gas-ports to push them out to seal.

He recommends the gapless top, napier 2nd ring and low tension (12-18lb) oil ring. They have an ultra low tension (9-11lb) ring for vac pump engines or where testing has proven it will work with a given engine combo. He claimed the gapless top ring is good for ~10hp. The napier 2nd ring has the little lip that catches and scrapes the oil and has slightly less drag.

The gapless top, Napier 2nd and low tension oil is about double the price of a standard set w/ the file fit moly top and std 2nd and low tension oil.

Rick


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 Post subject: Re: Gas Porting Pistons?
 Post Posted: Tue Feb 08, 2011 9:28 pm 
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I've seen a tenth in a few combinations that had 1/16th" rings. The only thing changed in the car, bumper to bumper, was me freshening the engine and adding gas ports to the combination.

Don

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 Post subject: Re: Gas Porting Pistons?
 Post Posted: Wed Feb 09, 2011 8:44 am 
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want-a-be wrote:
I've seen a tenth in a few combinations that had 1/16th" rings. The only thing changed in the car, bumper to bumper, was me freshening the engine and adding gas ports to the combination.

Don


Were you the original builder also? Were the rings standard radial thickness? or back-cut to reduce radial thickness/tension?

In a drag car? What engine combo? ci, rpm, compresison, vac pump etc?


A tenth is a fair amount to gain ... in a normal 600hp 2600# car that would be 20-25hp.

Thanks,
Rick


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 Post subject: Re: Gas Porting Pistons?
 Post Posted: Wed Feb 09, 2011 4:29 pm 
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The sealing ability of the ring package is the critical thing to power generation. The friction is not supposed to be there, thats why we use oil. The thing that changes the power output like claimed (the tenth) is a switch in chemistry of combustion due to increased compression efficiency. Gas porting pistons affects the rings on the compression stroke too. If the compression effort is not wasted by leakage then the chemistry will change. Any increase in compression increases power, its not just the effect of compression on the Carnot cycle although leakage is like running a lower comp ratio. The effect of heating the fuel and Oxygen molecules is the reason why you make speed of combustion and power, loose some of that heat (because your leaking pressure) and you get less efficient combustion.
If the gas porting is not needed to improve the seal during the power stroke then all your doing is loading the oil more and creating other issues that will show over time. Gas porting has 2 functional areas, forcing the rings out during compression is the one you want to use. However its necessity is related to the compression which is energy transfer into the fuel being used. For instance optimize the atomization and homogenization and fuel type and dynamic compression and then gas porting has less benefit.


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