Diamond piston/ring problem **UPDATE**
#2460715
03/04/18 02:15 AM
03/04/18 02:15 AM
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Joined: Aug 2009
Posts: 2,039 Mooresburg, Tn
'72CudaRacer
OP
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OP
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Joined: Aug 2009
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Mooresburg, Tn
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Anyone one here ever run into this?? Diamond custom pistons, piston card calls for 1/16 x 1/16 x 3/32 rings, 4.600 bore. I got Mahle rings, correct size and fitted them to the bore. When I try to load the piston into the cylinder, the piston gets stuck in the ring compressor (tapered sleeve, correct size). After getting the piston assembly unstuck (without damaging anything!!), and doing a lot of investigating, I find that the top ring is bottoming out in the piston. Everything else is fine. I go retrieve the old rings that came off these pistons and find that width of the old ring is .169" (not top to bottom, but from the face of the ring to the inside diameter). The new top ring is .194", and the ring gap in the cyl bore is correct at .021", but when it is on the piston and "bottomed out", the gap is in excess of .030" and the diameter of the ring at that point is in excess of 4.602". I have the actual work order from when the pistons were made and it list the rings as 4.600b 1/16ap x 1/16nap x 3/16std. At this point I'm standing here going WTH?? Any suggestions other than calling Diamond on Monday?
Thanks, Brian
Last edited by '72CudaRacer; 03/05/18 09:29 PM.
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Re: Diamond piston/ring problem
[Re: '72CudaRacer]
#2460721
03/04/18 02:41 AM
03/04/18 02:41 AM
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Joined: Oct 2006
Posts: 1,264 New York, USA
Chargerfan68
pro stock
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pro stock
Joined: Oct 2006
Posts: 1,264
New York, USA
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The rings must be the wrong radial thickness. The proper rings have to give you the proper back clearance. Iff the old rings were .069” and it gives you correct back clearance or gap, the new rings radial thickness is incorrect. Did diamond supply the rings to you? Some ring manufacturers will back cut the rings to thinner dimensions. I had total seal back ut my rings for example. Maybe those can be corrected?
1.50 60Ft. , 10.75@ 127MPH Hauling 3900 LBS.
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Re: Diamond piston/ring problem
[Re: Chargerfan68]
#2460728
03/04/18 02:57 AM
03/04/18 02:57 AM
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Joined: Aug 2009
Posts: 2,039 Mooresburg, Tn
'72CudaRacer
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Joined: Aug 2009
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Mooresburg, Tn
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Iff the old rings were .069” and it gives you correct back clearance or gap, The old rings were gapped for nitrous use (but not used), top ring gap was over .030". This owner will not use nitrous, that was one of the reasons for me fixing the engine. Brian
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Re: Diamond piston/ring problem
[Re: dvw]
#2460795
03/04/18 11:49 AM
03/04/18 11:49 AM
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Joined: Aug 2009
Posts: 2,039 Mooresburg, Tn
'72CudaRacer
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Call Total Seal and order the correct top rings. You can buy just the 8 you need. Doug Well Doug, this has to be the best news that I've heard yet. Thanks, Brian
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Re: Diamond piston/ring problem
[Re: Cab_Burge]
#2460796
03/04/18 11:51 AM
03/04/18 11:51 AM
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Joined: Aug 2009
Posts: 2,039 Mooresburg, Tn
'72CudaRacer
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OP
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If this is a street or non serious race motor have the piston ring grooves cut to the proper depth for these rings and make sure and get the back spacing depth correct also This is a 622 ci, for sure not a street engine. But I thought it might be a option. Brian
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Re: Diamond piston/ring problem
[Re: dvw]
#2460816
03/04/18 12:20 PM
03/04/18 12:20 PM
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Joined: Jan 2005
Posts: 4,243 Charlotte, North Carolina
sgcuda
master
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master
Joined: Jan 2005
Posts: 4,243
Charlotte, North Carolina
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Call Total Seal and order the correct top rings. You can buy just the 8 you need. Doug I agree. I wouldn't be machining pistons or rings. I would get the proper rings for the piston application. Modifying parts would only complicate matters down the road on the next freshen up.
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Re: Diamond piston/ring problem
[Re: '72CudaRacer]
#2460819
03/04/18 12:25 PM
03/04/18 12:25 PM
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Joined: Jan 2003
Posts: 19,361 Las Vegas
Al_Alguire
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 19,361
Las Vegas
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Just need the correct radial sized top ring. They are made in various sizes to fit various manufacturers piston specs.
"I am not ashamed to confess I am ignorant of what I do not know."
"It's never wrong to do the right thing"
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Re: Diamond piston/ring problem
[Re: Cab_Burge]
#2460887
03/04/18 02:10 PM
03/04/18 02:10 PM
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Joined: Apr 2005
Posts: 1,505 TN
SCATPACK 1
pro stock
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pro stock
Joined: Apr 2005
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TN
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If this is a street or non serious race motor have the piston ring grooves cut to the proper depth for these rings and make sure and get the back spacing depth correct also this. It should give you more ring control and less ring roll over or flutter at high RPM
Old Geezer Racing
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Re: Diamond piston/ring problem
[Re: Chuck@Best_Machine]
#2460905
03/04/18 02:31 PM
03/04/18 02:31 PM
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Joined: Aug 2009
Posts: 2,039 Mooresburg, Tn
'72CudaRacer
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OP
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Joined: Aug 2009
Posts: 2,039
Mooresburg, Tn
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Are you sure the radial on the old ring is .069 ? A normal backcut 1/6th ring is .170 and a normal non back cut is around.200 If you really needed a 1/16th (.062) backcut to .069 it would almost be square. If this is the case you have a piston problem I believe that you are correct, Sir. My mistake (I corrected my original post). A good reason why mechanics shouldn't try to be machinist when its late and they are tired and annoyed. Thank you. Brian
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Re: Diamond piston/ring problem
[Re: Chuck@Best_Machine]
#2460955
03/04/18 04:17 PM
03/04/18 04:17 PM
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Joined: Aug 2009
Posts: 2,039 Mooresburg, Tn
'72CudaRacer
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Your welcome. So all you need to fix this is a set of backcut rings Is a item that would be on the shelf or is it a custom thing? Doug suggested Total Seal, sounds like he has experience. Brian
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