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Author
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Topic: Today's lesson...ring end gaps!
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2stangs69-91
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Member # 1951
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posted
 
 
hmmm are they probe pistons ? The reason I ask is my 331 has one of those also after 2 years of pounding. I set the ring gaps on my engine(for a SC aplication) as I have on many others also with never a problem. On my 410 I am building I went with much bigger gaps then asked for on a SC aplication, I am leaning towards a leanout on mine just because this is also the area were it would fail. I have one more that is not broken but you can tell it was just starting to melt.
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69 Mustang on hold
1991 LX hatch getting a make over
1994 F150 4X4 351
2006 Yamaha V-max 1200 Modded
Posts: 3711 | From: Redding | Registered: Oct 2002
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AJBlackGT
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Member # 3936
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posted
That model piston seems to always break at the same spot, right at the valve relief. It might not be improper ring end gaps on all of these, maybe its just a bad design. How much meat is there between the bottom of the valve relief and the top of the first ring? My srp's have .250 of material in this area, but I have blown off the second ring land ![[Confused]](confused.gif) That one piston that broke with all the little ring pieces looks like it leaned out rather than breaking due to insufficient ring gap.
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90 Notch
Posts: 1896 | From: Sacramento | Registered: Dec 2003
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BlueOvalRacing
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Member # 1531
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posted
It doesn't make a difference who makes the piston, it will almost always break at the point of least material. Running an engine lean increases the heat in the cylinder, much like adding cylinder pressure does in a supercharged apllication. That heat increses the expansion of the rings/pistons/cylinder, and the end result, just like water or electricity, follows the path of least resistance.
Don't be too quick to blame the piston manufacturer for what is most likely a builder oversight.
Posts: 1159 | From: Pioneer | Registered: Jul 2002
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2stangs69-91
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Member # 1951
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why do you say builder oversight? pro engine builders who do everything correctly have engine failures? Do you think in my case after 2 years hundreds of passes about 20,000 miles I did something wrong when I built it? I think I had a lean out. Normaly build problems show up pretty early.
[ October 25, 2006, 08:29 PM: Message edited by: 2stangs69-91 ]
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69 Mustang on hold
1991 LX hatch getting a make over
1994 F150 4X4 351
2006 Yamaha V-max 1200 Modded
Posts: 3711 | From: Redding | Registered: Oct 2002
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Becca
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Member # 7004
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I'd say this one was builder error, the car was N.A. and only ran about 7 AUTOCROSS events! Its been up and down the last year and a half barely has any time/miles on it.
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Happiness isn't around the corner, happiness IS the corner!
'00 Silverado 1500 LT
'91 Mustang GT
Posts: 111 | From: San Jose, CA | Registered: Aug 2006
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AJBlackGT
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Member # 3936
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posted
quote:
Originally posted by BlueOvalRacing:
It doesn't make a difference who makes the piston, it will almost always break at the point of least material. Running an engine lean increases the heat in the cylinder, much like adding cylinder pressure does in a supercharged apllication. That heat increses the expansion of the rings/pistons/cylinder, and the end result, just like water or electricity, follows the path of least resistance.
Don't be too quick to blame the piston manufacturer for what is most likely a builder oversight.
Yes I agree, but why put in a piston with less material above the top ring if you know it will fatigue earlier
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90 Notch
Posts: 1896 | From: Sacramento | Registered: Dec 2003
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BlueOvalRacing
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Member # 1531
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posted
quote:
Originally posted by 2stangs69-91:
why do you say builder oversight? pro engine builders who do everything correctly have engine failures? Do you think in my case after 2 years hundreds of passes about 20,000 miles I did something wrong when I built it? I think I had a lean out. Normaly build problems show up pretty early.
Calm down. Less than .001" could mean the difference between lifting a ring land or the engine being fine for any given mileage. With 20k miles, did you ever consider carbon build-up in the ring land as a possible reason for the gap closing up? Build problems can occur at any point in an engine's life, it depends on what actually caused the problem, not just what you see is broken.
In your case, if you feel it leaned out, my original point about cylinder temps stands.
You need to explain to me how the piston manufacturer is at fault. I have them (Probe) in my n/a 331 with well over 20k miles, and no problems. Maybe I set the ring gap correctly for my application, knowing it would never see boost. Maybe you needed that extra .001"
Posts: 1159 | From: Pioneer | Registered: Jul 2002
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BlueOvalRacing
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Member # 1531
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posted
quote:
Originally posted by AJBlackGT:
quote:
Originally posted by BlueOvalRacing:
It doesn't make a difference who makes the piston, it will almost always break at the point of least material. Running an engine lean increases the heat in the cylinder, much like adding cylinder pressure does in a supercharged apllication. That heat increses the expansion of the rings/pistons/cylinder, and the end result, just like water or electricity, follows the path of least resistance.
Don't be too quick to blame the piston manufacturer for what is most likely a builder oversight.
Yes I agree, but why put in a piston with less material above the top ring if you know it will fatigue earlier
You are always free to use someone else's piston. More than likely, you won't find one that varies much from Probe's design. The valve relief issue only seems to show up under leaned out boosted applications or builder error, or a combination of both.
Posts: 1159 | From: Pioneer | Registered: Jul 2002
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AJBlackGT
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Member # 3936
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posted
I have srps in my motor. They measure .250" from the top ring to the bottom of the valve relief. I'm not sure how the probe's measure though...
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90 Notch
Posts: 1896 | From: Sacramento | Registered: Dec 2003
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2stangs69-91
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Member # 1951
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lol I am calm I don't have carbon build up and I don't have a ring gap issue either. If mine was NA I doubt there would of ever been a problem. Build issues show up very early in engine life or it wouldn't be a issue Duh LOL
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69 Mustang on hold
1991 LX hatch getting a make over
1994 F150 4X4 351
2006 Yamaha V-max 1200 Modded
Posts: 3711 | From: Redding | Registered: Oct 2002
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JohnB
Tech Moderator
Member # 969
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posted
Update: piston pulled, ring gap checked...
.014!!! No wonder why it gave up!
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6523 | From: Orlando FL/Redding CA | Registered: Mar 2002
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BlueOvalRacing
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Member # 1531
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Hey, how about that.... Whoda thunk it?
Posts: 1159 | From: Pioneer | Registered: Jul 2002
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2stangs69-91
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Member # 1951
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nice find it is nice to verify way to tight. Thats why my blower set up was .024 ![[Roll Eyes]](rolleyes.gif)
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69 Mustang on hold
1991 LX hatch getting a make over
1994 F150 4X4 351
2006 Yamaha V-max 1200 Modded
Posts: 3711 | From: Redding | Registered: Oct 2002
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