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Houston, we have a problem! ( or two) #2759861
04/04/20 02:06 PM
04/04/20 02:06 PM
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Frostbitefalls MN (Rocky&Bullw...
gregsdart Offline OP
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While checking my pistons I spotted a "ding" right dead center of the top ring grove. Sure enough, damaged enough to not allow a ring to go in the grove. Damage isn't real deep as I was able to put a used ring in the groove, slide it under the damaged area, and use it as a scraper to cut through some of the tight spot. But I still need to open it up enough so the ring does'nd bind there. Ideas??
2nd problem. It looks like my top rings were butting slightly, enough to leave a little shiny spot on the outer side of the ring gap surfaces. Those were set at .0045 per inch of bore. (.0225) I am going to go out .0025 more to .025 or unless I get feed back that I should go more, I will.

20200404_124129.jpg
Last edited by gregsdart; 04/04/20 02:17 PM.

8.77 153 mph best, 3055 lbs 528 indy 440-1 alky
Re: Houston, we have a problem! ( or two) [Re: gregsdart] #2760021
04/04/20 03:18 PM
04/04/20 03:18 PM
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Upstate NY
Bigcube Offline
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I would go more than that. I ran .032 top and .036 2nd ring. I had set up to take a small shot of nitrous but was told it won't make much difference for NA. That was at 4.440" bore. Never showed signs of them touching on tear downs.

Last edited by Bigcube; 04/04/20 03:19 PM.

Jim

Re: Houston, we have a problem! ( or two) [Re: gregsdart] #2760022
04/04/20 03:19 PM
04/04/20 03:19 PM
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Great Neck,LI,new york
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I am no expert but my guess is you went lean and that spot is the path of least resistance.

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Re: Houston, we have a problem! ( or two) [Re: gregsdart] #2760030
04/04/20 03:23 PM
04/04/20 03:23 PM
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Washington
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Is it just a raised lip out at the edge of the groove, or is it down further back??? If it’s just out there on the edge of the groove I’d just get that raised area that is hanging down into the groove out of there. If you do that and the ring isn’t pinched in the groove I think you’ll be ok. As long as you know what did that.

If you are going to open the gap up only .0025 you will be taking less than .001 off the end of the ring, if I’m understanding what you are saying. .001 off the ring will get you .00314159 more gap. My point is if you take .003-.004 off the end of the rings and the gap will gain about .010 or a bit more I wouldn’t worry about that. The rings butting will cost more power than a slightly larger gap.


Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
Re: Houston, we have a problem! ( or two) [Re: madscientist] #2760063
04/04/20 05:23 PM
04/04/20 05:23 PM
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Las Vegas
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If you are concerned with doing the work or feel its something someone should look at check out for get with Eric at Rebco. They can fix just about anything short of a hole in a piston.


Rebco Machine, Inc.
1100 W 37th St N
Wichita, KS 67204

Re: Houston, we have a problem! ( or two) [Re: Al_Alguire] #2760099
04/04/20 06:33 PM
04/04/20 06:33 PM
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MI, usa
dvw Offline
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I've had mine apart to check. The rings are not butting. 4.505 bore, .026" gap. 15-1 compression, 7300 max if either of that matters.
Doug

Re: Houston, we have a problem! ( or two) [Re: dvw] #2760135
04/04/20 07:49 PM
04/04/20 07:49 PM
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Frostbitefalls MN (Rocky&Bullw...
gregsdart Offline OP
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Originally Posted by dvw
I've had mine apart to check. The rings are not butting. 4.505 bore, .026" gap. 15-1 compression, 7300 max if either of that matters.
Doug

Doug your comment in another post got my attention. Since you have used .026 with good luck I think I will follow suit. As for the damaged ring grove, the cause is obvious when magnified. It looks like a gremlin hit the piston with a small ballpeen hammer! Round indent with the gap pinched right in the middle.
Al, I think I will ship the piston to Cp if they will fix it or maybe Rebco. [s][/s] Better to let a pro do it. It just took a little time for the ole brain to come up with the logical move. I have heard some ring grooves are cut at a very minor slant so they are straight at running temp.

Last edited by gregsdart; 04/04/20 07:51 PM.

8.77 153 mph best, 3055 lbs 528 indy 440-1 alky
Re: Houston, we have a problem! ( or two) [Re: gregsdart] #2760176
04/04/20 09:37 PM
04/04/20 09:37 PM
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Bend,OR USA
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Do you still have any point files? If so I would, and have, fix it now instead of shipping it our or replacing it wrench Stuff happens whiney


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Houston, we have a problem! ( or two) [Re: Cab_Burge] #2760287
04/05/20 09:26 AM
04/05/20 09:26 AM
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Western NC
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I am a little surprised that 0.0225" top ring end gap wasn't enough for Normally Aspirated application, alcohol.
That being said, from what you see, 0.026" should get the job done, IMO.

Is your top ring groove closer than 0.250" from the piston top? Doesn't look like it, but that could be a factor.

Jim

Re: Houston, we have a problem! ( or two) [Re: gregsdart] #2760295
04/05/20 09:48 AM
04/05/20 09:48 AM
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10 thumbs up for Eric at Rebco Machine if your nervous about it. Had situation like that awhile back. My wife bailed me out. Got a true fingernail file off of her and spent some very careful time with it. For what is worth, it was made by Revlon. LOL

Re: Houston, we have a problem! ( or two) [Re: Cab_Burge] #2760296
04/05/20 09:50 AM
04/05/20 09:50 AM
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Frostbitefalls MN (Rocky&Bullw...
gregsdart Offline OP
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Originally Posted by Cab_Burge
Do you still have any point files? If so I would, and have, fix it now instead of shipping it our or replacing it wrench Stuff happens whiney

Good idea Cab.
Jim, on the end gap I have been running .0045/ inch of bore for a Long time. I am not sure why this showed up? Apparently I need a touch more safety margin.


8.77 153 mph best, 3055 lbs 528 indy 440-1 alky
Re: Houston, we have a problem! ( or two) [Re: 440Jim] #2760299
04/05/20 09:54 AM
04/05/20 09:54 AM
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Apollo, PA.
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I have fixed pistons that have crunched a ring land from a foreign object (head of a carb butterfly screw) getting between the head and piston and pinching the ring. Fixed with a small file. Car never changed et ...even before catching the problem.
A butted ring ,even slightly, will score the bore badly. What does the bore look like?

Re: Houston, we have a problem! ( or two) [Re: madscientist] #2760300
04/05/20 09:58 AM
04/05/20 09:58 AM
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Originally Posted by madscientist
If you are going to open the gap up only .0025 you will be taking less than .001 off the end of the ring, if I’m understanding what you are saying. .001 off the ring will get you .00314159 more gap. My point is if you take .003-.004 off the end of the rings and the gap will gain about .010 or a bit more I wouldn’t worry about that. The rings butting will cost more power than a slightly larger gap.


This is incorrect information, the gap yields a net change for whatever you file off because you are not changing the circumference of the bore.
Now if the bore got increased by .001 then yes the gap would increase by .0031

Re: Houston, we have a problem! ( or two) [Re: B1MAXX] #2760379
04/05/20 01:11 PM
04/05/20 01:11 PM
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Frostbitefalls MN (Rocky&Bullw...
gregsdart Offline OP
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Originally Posted by B1MAXX
I have fixed pistons that have crunched a ring land from a foreign object (head of a carb butterfly screw) getting between the head and piston and pinching the ring. Fixed with a small file. Car never changed et ...even before catching the problem.
A butted ring ,even slightly, will score the bore badly. What does the bore look like?

B 1 the bores looked ok except for scratches from another issue. I figure the butting was very light, like maybe .001 too tight at some point when the motor was lean or warmer than normal.


8.77 153 mph best, 3055 lbs 528 indy 440-1 alky
Re: Houston, we have a problem! ( or two) [Re: gregsdart] #2760716
04/06/20 12:10 PM
04/06/20 12:10 PM
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Apollo, PA.
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if it didn't tear the bore up then your just right panic even .001 of neg. gap would be sawzall

Re: Houston, we have a problem! ( or two) [Re: Cab_Burge] #2760731
04/06/20 12:39 PM
04/06/20 12:39 PM
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Frostbitefalls MN (Rocky&Bullw...
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Originally Posted by Cab_Burge
Do you still have any point files? If so I would, and have, fix it now instead of shipping it our or replacing it wrench Stuff happens whiney

Cab, I have .043 rings and the file I bought was about .050. But it worked out very well. I just sanded down one side till the file would barely fit the grove and it cleaned the pinch spot up nicely. No more tight spot.👍thanks😁


8.77 153 mph best, 3055 lbs 528 indy 440-1 alky
Re: Houston, we have a problem! ( or two) [Re: gregsdart] #2761215
04/07/20 06:19 PM
04/07/20 06:19 PM
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Frostbitefalls MN (Rocky&Bullw...
gregsdart Offline OP
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Now we have another problem.😒Mr cLutz hear broke a second ring while filing😣Man that 043 ring snapped easily😳

Last edited by gregsdart; 04/07/20 06:20 PM.

8.77 153 mph best, 3055 lbs 528 indy 440-1 alky
Re: Houston, we have a problem! ( or two) [Re: gregsdart] #2761294
04/07/20 10:25 PM
04/07/20 10:25 PM
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Bend,OR USA
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Welcome to the club up grin Did it break after you got the gap where you wanted it?
Mine normally do whiney shruggy
I had one 5/16 ring break that had a small bubble in the metal it in the middle of the ring away from the gap, I was using my ring expander installation tool to install that ring in a groove when it failed shock
I' m glad it broke before it went into the engine up work


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Houston, we have a problem! ( or two) [Re: Cab_Burge] #2761523
04/08/20 02:45 PM
04/08/20 02:45 PM
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Las Vegas
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Greg just t=send them to Rebco, I'm sure if you call CP they will recommend them as well. I had m predator pistons ring lands recut by Rebco for additional radial clearance and thicker rings. Have used them a few times for damaged ring lands as well. FWIW all my stuff is from CP

Re: Houston, we have a problem! ( or two) [Re: Al_Alguire] #2761598
04/08/20 05:24 PM
04/08/20 05:24 PM
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gregsdart Offline OP
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Thanks Al. I will catalog thier info. I did get the pinch removed by carefully working with a points file. Hopefully this will keep me going for a while.


8.77 153 mph best, 3055 lbs 528 indy 440-1 alky
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