What does the damage look like from small ring gap?
09-27-2008, 06:16 PM
#1
What does the damage look like from small ring gap? I did a compression check and found low so I pulled number 7. The top ring was completly closed and had no gap. The second ring had about 1/2" or the outer area broken off. The top ring was kinda seized, after soaking in carb cleaner I was able to spin it around but the gap was still very small.
Could it have gotten so hot that it lost is spring? A sponsor on here built the engine and I haven't talked to them yet to see what the gap was set at. I put the 2nd ring in the motor and it looks to be gapped at .018". Also the center of the outer ring lost metal all the way around it looked like carbon but after looking closer it is actually pitted.
These are total seal rings.
Could it have gotten so hot that it lost is spring? A sponsor on here built the engine and I haven't talked to them yet to see what the gap was set at. I put the 2nd ring in the motor and it looks to be gapped at .018". Also the center of the outer ring lost metal all the way around it looked like carbon but after looking closer it is actually pitted.
These are total seal rings.
09-29-2008, 08:24 AM
#5
I have this post going which contains a lot of discussion on ring gap on FI cars. First time I heard of it being an issue.
http://forums.corvetteforum.com/show...post1567282812
http://forums.corvetteforum.com/show...post1567282812
09-29-2008, 01:14 PM
#6
From the pics, I would steer toward detonation.
I would not expect to see the scuffs on the thrust side of the piston if the problem was isolated to inadequate ring gap only.
Also, you can check the bores for vertical scratches to see if the rings were butting.
I would not expect to see the scuffs on the thrust side of the piston if the problem was isolated to inadequate ring gap only.
Also, you can check the bores for vertical scratches to see if the rings were butting.
09-29-2008, 06:27 PM
#7
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You can see the moly broken off the top ring, this is a result of detonation.
With that much detonation and the resulting loss of seal on the top ring the second ring broke shortly thereafter.
The top ring probably lost it's tension due to overheating which is why there is no gap left in the pic. To check the top ring gap put it in the bore and chek the gap with a feeler gauge.
With that much detonation and the resulting loss of seal on the top ring the second ring broke shortly thereafter.
The top ring probably lost it's tension due to overheating which is why there is no gap left in the pic. To check the top ring gap put it in the bore and chek the gap with a feeler gauge.
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09-29-2008, 07:26 PM
#8
You can see the moly broken off the top ring, this is a result of detonation.
With that much detonation and the resulting loss of seal on the top ring the second ring broke shortly thereafter.
The top ring probably lost it's tension due to overheating which is why there is no gap left in the pic. To check the top ring gap put it in the bore and chek the gap with a feeler gauge.
With that much detonation and the resulting loss of seal on the top ring the second ring broke shortly thereafter.
The top ring probably lost it's tension due to overheating which is why there is no gap left in the pic. To check the top ring gap put it in the bore and chek the gap with a feeler gauge.
Unless the diamond pistons are just that good I would have expected a little bit of damage to the tops of the pistons also. In th 6th pic down you can see the only damage to the piston is a small hot spot. I did have a couple of runs at the track where I had fuel pressure issues and I know it went lean, which is probably when this happened. BUt I wasn't sure why the top ring was completely closed up. Like you said I thought maybe the excessive heat may have caused it but I have never seen that before. I've since soaked it to remove all the carbon and it appears that the ring lands are not bent up and there are not any scratches in the cylinder (no more than any of the others that had good compression). So I guess I am going to rering it and hope it all happened from the couple of runs with the lean spike at the track.
I agree the 2nd one broke because it was basically being used like a top ring instead and it is 1/2 as thick.
09-29-2008, 08:45 PM
#9
The second ring is a napier ring. You can break them installing them if you're not careful. They're shaped like an upside down "L"
I'd like to see the tops of the pistons and the plug before I said it was detonation.
I've seen holes blown in pistons from detonation, and the rings be pretty much fine.
The broken ring could be from installation. The moly chipping off could be from grit from the second ring pieces floating around. I don't see how detonation is going to blow the moly off the rings, but the piston crown, which takes the brunt of the heat, and the hammer force of detonation, not be affected.
I'd like to see the tops of the pistons and the plug before I said it was detonation.
I've seen holes blown in pistons from detonation, and the rings be pretty much fine.
The broken ring could be from installation. The moly chipping off could be from grit from the second ring pieces floating around. I don't see how detonation is going to blow the moly off the rings, but the piston crown, which takes the brunt of the heat, and the hammer force of detonation, not be affected.
Last edited by edcmat-l1; 09-29-2008 at 08:52 PM.
