Author Topic: Piston ring end gap  (Read 788 times)

Offline Wadmin1021

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Piston ring end gap
« on: July 11, 2016 - 07:42:00 pm »
Piston ring end gap question. 440 bored .030 over for 4.350 inch bore. Our piston rings measure top: .025 and second is .024. Everything I've read on this forum and others says top end ring gap should be smaller. 0.0045x4.350 for top and 0.0055x4.350 for second. They are Sealed Power and no ring end gap came with instructions. Thoughts?


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Online Chryco Psycho

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Re: Piston ring end gap
« Reply #1 on: July 11, 2016 - 09:17:28 pm »
 :iagree:
 Gap should be closer to .018 -.020
but .006 is approx 2x the diameter of a hair
make sure you place the gaps 180* apart , never line them up

Challenger - You`ll wish You Hadn`t

Offline 734406pk

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Re: Piston ring end gap
« Reply #2 on: July 11, 2016 - 09:29:40 pm »
Try Federal Mogul Tech Support:

http://www.fmmotorparts.com/fmstorefront/federalmogul/en/USD/support/technical-line

Those ring gaps you have posted are general spec. btw. SP rings are usually gapped to the stock engine spec. My manual states; Top ring .013" to .023", second ring .013"-.023" and the oil control ring same at .013" to .023". These are factory clearances. FM specs could be different. Too little clearance will lead to engine damage.
1973 Challenger 440 6 pack auto 3.91 rear
2012 Dodge Ram 3500 dually 6.7 Cummins Fleece EFI Live
1973 Challenger 318 2bbl auto 2.73 rear 22.5 mpg RIP
1970 Challenger TA 340 4bbl auto-Sold and sad
1999 Dodge Ram 3500 dually 5.9 Cummins Fleece tuned VGT-sold
1995 Kawasaki ZX1100E & still alive


Offline 73restomod

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Re: Piston ring end gap
« Reply #3 on: July 12, 2016 - 08:49:22 am »
So often times I've seen small motors lock up because to little clearance on ring gaps. Especially air cooled ones, your better off being a little loose, still in tolerance of course, than you are being as tight as you can possibly get it. I say that mostly because it gives some margin for error if the motor was to overheat. Which is more of a problem with small motors that turn 8-16k rims, than it is our old iron. Lol when I build my motors I spec between hot street and endurance racing tables becuase of my right foot tendencies.

Offline Wadmin1021

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Re: Piston ring end gap
« Reply #4 on: July 12, 2016 - 09:10:49 am »
HAHAHA thanks! I called Federal Mogul just to be sure - THANKS 734406pk - and they said that our rings are set for a 440 engine bored 0.030 which is what ours is. According to FP, they are filed to fit a 0.030 bore. 0.023-0.025 is the standard ring gap for a 440 engine bored 0.030 over. The only time you will have to modify or change this ring end gap is for racing applications or with extremely high RPM's. So we are good and he assured me that this is to spec and both ring end gaps are good with no need to modify.


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A couple that plays together, stays together!

'71 Plymouth 'Cuda named Claudia w/ 440 4-barrel and TF AT

Offline 734406pk

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Re: Piston ring end gap
« Reply #5 on: July 12, 2016 - 11:15:00 pm »
So often times I've seen small motors lock up because to little clearance on ring gaps. Especially air cooled ones, your better off being a little loose, still in tolerance of course, than you are being as tight as you can possibly get it. I say that mostly because it gives some margin for error if the motor was to overheat. Which is more of a problem with small motors that turn 8-16k rims, than it is our old iron. Lol when I build my motors I spec between hot street and endurance racing tables becuase of my right foot tendencies.
:2thumbs: This is True!!
1973 Challenger 440 6 pack auto 3.91 rear
2012 Dodge Ram 3500 dually 6.7 Cummins Fleece EFI Live
1973 Challenger 318 2bbl auto 2.73 rear 22.5 mpg RIP
1970 Challenger TA 340 4bbl auto-Sold and sad
1999 Dodge Ram 3500 dually 5.9 Cummins Fleece tuned VGT-sold
1995 Kawasaki ZX1100E & still alive

Offline 734406pk

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Re: Piston ring end gap
« Reply #6 on: July 12, 2016 - 11:18:50 pm »
HAHAHA thanks! I called Federal Mogul just to be sure - THANKS 734406pk - and they said that our rings are set for a 440 engine bored 0.030 which is what ours is. According to FP, they are filed to fit a 0.030 bore. 0.023-0.025 is the standard ring gap for a 440 engine bored 0.030 over. The only time you will have to modify or change this ring end gap is for racing applications or with extremely high RPM's. So we are good and he assured me that this is to spec and both ring end gaps are good with no need to modify.


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Very Good! It doesn't hurt to double check engine specs IMO. You only want to do this job once. :2thumbs:
1973 Challenger 440 6 pack auto 3.91 rear
2012 Dodge Ram 3500 dually 6.7 Cummins Fleece EFI Live
1973 Challenger 318 2bbl auto 2.73 rear 22.5 mpg RIP
1970 Challenger TA 340 4bbl auto-Sold and sad
1999 Dodge Ram 3500 dually 5.9 Cummins Fleece tuned VGT-sold
1995 Kawasaki ZX1100E & still alive