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1G Piston to cylinder wall clearance

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915dsm

10+ Year Contributor
202
0
Nov 9, 2010
El Paso, Texas
Anyone in here can shine some light on recommendations for piston to cylinder wall clearances for my 2.3 wiseco pistons?

The suggested clearance is
.0024"
Should i use this clearance?

Those with serious builts, what are you using for piston to wall and ring clearences?
 
Any piston slap on cold startup?
How much boost you running?
Are this engines still running? If they are not, did you disassemble them and see how the pistons look?


PTW for my Wiseco HD's on my 2.0 was .0045"
PTW for my Ross pistons on my 2.0 were .006"
 
Any piston slap on cold startup?
How much boost you running?
Are this engines still running? If they are not, did you disassemble them and see how the pistons look?[/QUOTE



I just called Wiseco. The recommendations for my application as street/strip is to be .0035-.0040". No more than that.

If its drags only. Then no more than .0045".

Any thoughts?
 
Any piston slap on cold startup?
How much boost you running?
Are this engines still running? If they are not, did you disassemble them and see how the pistons look?

Both pistons slap on startup. The wiseco's goes away at operating temp, the ross' slapped no matter what. The ross motor is no longer running. Snapped a wrist pin after 3yrs+ of abuse. Walls and pistons showed normal wear...nothing I was concerned about.

Wiseco motor only has about 600mi on it right now.

I run 30-35psi on a 60lb/min turbo.
 
What about ring clearences for top and bottom rings?
What are your specs on the wiseco pistons?

Both pistons slap on startup. The wiseco's goes away at operating temp, the ross' slapped no matter what. The ross motor is no longer running. Snapped a wrist pin after 3yrs+ of abuse. Walls and pistons showed normal wear...nothing I was concerned about.

Wiseco motor only has about 600mi on it right now.

I run 30-35psi on a 60lb/min turbo.
 
The consensus seems to be .020 gap for the top ring, and .024 gap for the second ring.

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If you're planning on a good sized turbo running a good bit of boost, you want looser specs than stock.

Stock Specs:
No. 1 ring 0.25 - 0.40mm (.0098 - .0157")
No. 2 ring 0.45 - 0.60mm (.0177 - .0236")

converted to inches, 85.5mm = 3.36614

for first ring, 3.36614 x .0060 = 0.02019 ~ .020
for second ring, 3.36614 x .0070 = 0.2356 ~ .024

You run stock ring gaps on high boost/hp application and you can say good bye to that block. The Wiseco directions in my picture are legible, yes ?
 
Yes they are legible. Thank you for the info. Bud. You just solved my mathamatical problem.

What you just calculated is exactly what wiseco said, but this are the minimal specs. Meaning i can go mor? But why would i want do that?


If you're planning on a good sized turbo running a good bit of boost, you want looser specs than stock.

Stock Specs:
No. 1 ring 0.25 - 0.40mm (.0098 - .0157")
No. 2 ring 0.45 - 0.60mm (.0177 - .0236")

converted to inches, 85.5mm = 3.36614

for first ring, 3.36614 x .0060 = 0.02019 ~ .020
for second ring, 3.36614 x .0070 = 0.2356 ~ .024

You run stock ring gaps on high boost/hp application and you can say good bye to that block. The Wiseco directions in my picture are legible, yes ?
 
Why did you multiply by .006 for the first ring if its not on the chart?

If you're planning on a good sized turbo running a good bit of boost, you want looser specs than stock.

Stock Specs:
No. 1 ring 0.25 - 0.40mm (.0098 - .0157")
No. 2 ring 0.45 - 0.60mm (.0177 - .0236")

converted to inches, 85.5mm = 3.36614

for first ring, 3.36614 x .0060 = 0.02019 ~ .020
for second ring, 3.36614 x .0070 = 0.2356 ~ .024

You run stock ring gaps on high boost/hp application and you can say good bye to that block. The Wiseco directions in my picture are legible, yes ?
 
Honestly, I did poke around myself and found answers, but most of my information comes from Josh @ JNZ. We're old-school buds, and I'm not sure if anyone has worked on more dsm's than he has, or has overall general knowledge like he does. Sure this is my 15th dsm, but this is the first time I ever had machine work done. And since I was assembling it myself, that meant gapping the rings for the first time in my life.

So once I did my own searching and finding the general consensus on .020/.024 combo, I then asked him what gap to use, didn't say anything about what I was doing, bore, or otherwise, and he confirmed .020 and .024.

So I just interpolated that and did my own math, to kind of find out where I'd be on the Wiseco charts, using his recommendation. Essentially I knew the end result, and just worked the math backwards to see where it would fall on the charts in the pic.

Bigger gap means safer under huge horsepower, but also means more blow-by. You have to figure out what the right combination will be for YOU.
 
Honestly, I did poke around myself and found answers, but most of my information comes from Josh @ JNZ. We're old-school buds, and I'm not sure if anyone has worked on more dsm's than he has, or has overall general knowledge like he does. Sure this is my 15th dsm, but this is the first time I ever had machine work done. And since I was assembling it myself, that meant gapping the rings for the first time in my life.

So once I did my own searching and finding the general consensus on .020/.024 combo, I then asked him what gap to use, didn't say anything about what I was doing, bore, or otherwise, and he confirmed .020 and .024.

So I just interpolated that and did my own math, to kind of find out where I'd be on the Wiseco charts, using his recommendation. Essentially I knew the end result, and just worked the math backwards to see where it would fall on the charts in the pic.

Bigger gap means safer under huge horsepower, but also means more blow-by. You have to figure out what the right combination will be for YOU.



Well its my first time also and confused as I get many opinions. im not going on crazy horsepower. maybe 600 ponies. ive been recommended .0055" PTW clearance, .0024"top ring and .0020" for lower by a racer with over 15 years experience.

im pulling my dam hairs cause I want to follow his guidance but everyone else contradicts.
 
The reason you run ring gap in the top ring is to keep them from butting together and seizing your engine. When they get hot from running they will expand. The more power you make the hotter they get, the more they expand.

Generally you run a bit more gap on the second ring so that any gasses that do escape the top ring, and not build pressure. If it builds pressure it can unseat the top ring and cause blowby.

The clearances your racer is recommending are good and safe. I think .0055" PTW is a bit large. I'd suggest .004, and spend at least 1000mi of easy street use to get it broke in well.

Also think how small the ring end gap really is. Think how fast the piston is moving. It can only leak for about .004s each power pulse. How much is really going to leak?

My last motor was coated JE's with .004ptw, maybe 20 and 22 on the ring end gaps. Motor had very little blow by, great compression, after 2 seasons of abuse the shortblock was still fine. The pistons looked great and will be reused. I was making ~600whp.

Also as a comparison point. my first motor at the end was shot, huge blowby, big scratches in the cyl walls, .006" ptw. It trapped 130 at its best. built a new motor, basically identical. I was dissapointed when it only trapped 131 under similar conditions.
 
I am the guy he has been contacting. All our cars are in the 800-1000hp plus range. Those are the specs we use for any piston. I would never run a Wiseco piston myself but, I treat them all the same. We have no blow by and no issues other than one car not having valve cover baffles. We play in big boy land and have happy, reliable motors. And all this talk of scarring we have never experienced. Especially once we got our engine program under control. Two cars over 200mph and 5-6 cars hovering near 1000hp is where my experience comes from.
 
Well its my first time also and confused as I get many opinions. im not going on crazy horsepower. maybe 600 ponies. ive been recommended .0055" PTW clearance, .0024"top ring and .0020" for lower by a racer with over 15 years experience.

im pulling my dam hairs cause I want to follow his guidance but everyone else contradicts.
The reason you run ring gap in the top ring is to keep them from butting together and seizing your engine. When they get hot from running they will expand. The more power you make the hotter they get, the more they expand.

Generally you run a bit more gap on the second ring so that any gasses that do escape the top ring, and not build pressure. If it builds pressure it can unseat the top ring and cause blowby.

The clearances your racer is recommending are good and safe. I think .0055" PTW is a bit large. I'd suggest .004, and spend at least 1000mi of easy street use to get it broke in well.

Also think how small the ring end gap really is. Think how fast the piston is moving. It can only leak for about .004s each power pulse. How much is really going to leak?

My last motor was coated JE's with .004ptw, maybe 20 and 22 on the ring end gaps. Motor had very little blow by, great compression, after 2 seasons of abuse the shortblock was still fine. The pistons looked great and will be reused. I was making ~600whp.

Also as a comparison point. my first motor at the end was shot, huge blowby, big scratches in the cyl walls, .006" ptw. It trapped 130 at its best. built a new motor, basically identical. I was dissapointed when it only trapped 131 under similar conditions.



then .0024" top ring is looser and .0020" is tighter for lower ring? isn't this the opposite to what you ran on the JEs with .004" ptw?
 
I had a 30 minute conversation with Nick Arias about that. He promised me I would see no combustion and burning past the top of the piston. And both times my motor has been apart he was 100% right.
 
I had a 30 minute conversation with Nick Arias about that. He promised me I would see no combustion and burning past the top of the piston. And both times my motor has been apart he was 100% right.
What does this have to do with the OP's post? It's called quenching, and you can look up the minimum quenching distance for almost any fuel in any decent thermochemistry book.

OP, having a wider top ring will probably be fine. Noone really knows the answer, as there is no way to see what is really happening.

In any case I would probably take the word of the piston manufacturer. If you called wiseco and told them what you were going to do they are going to say .004-.005" of PTW, and .006" per inch of bore on the top, and .007"/in of bore on the bottom.
 
I was reluctant to switch the gaps. I had the man himself tell me the success they have had with experimenting reversing the gaps. I have torn down more motors than most guys have probably ever seen in running and driving dsms down the road. To see combustion getting past the second and oil controls rings is not uncommon. Obviously keeping the burn on top where the compression actually happens is much more efficient. And less prone to melting the edge of the piston.

That is what it had to do with his post. He asked if it was okay. I am here to prove it is. He can do what ever likes. He can light the thing on fire and drive it off a cliff for all I care as it does not benefit me. He wants a reliable engine and asked for m opinion. I gave him a few things we do in our engine program. He can take it or leave it. But, for people to not think outside their little box or have no experience or answers to why they did something is why I spoke up. Real world proven experience. We have tried it all and found out what certainly will not work and what kicks ass.

My vote it light it on fire or blow it up and don't even deal with the process. It is all a waste of time and money anyway.
 
Ok, well, pretty much if the clearance is less than about 0.040" the flames go out. It's pressure dependant, but it's scientific fact. If you have fire on the sides of your pistons because 0.006" of clearance, you have much much bigger problems. Most of what you see on the piston between the rings is just cooked oil. I'm sure if you tried really really hard you could get some hot gasses to blow through there and scorch some stuff, but there will never ever be flame in there.
 
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