390 piston rings

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Mar 28, 2001 | 11:02 PM

phaffy12

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Junior User

Joined: Mar 2001

Posts: 79

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From: Granger, IA

390 piston rings

As I understand, the 390 has a bore diameter of 4.050". Does this mean that replacement rings should be of 4.000" diameter? Thanks for any help.

Mar 29, 2001 | 03:25 PM

dinosaurfan

Cargo Master

Joined: Aug 2000

Posts: 2,931

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From: SW Michigan

390 piston rings

Matt, yes your 390 has a 4.050 bore and that is the size your rings need to be, 4.050 DF

Mar 29, 2001 | 11:22 PM

phaffy12

Thread Starter

Junior User

Joined: Mar 2001

Posts: 79

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From: Granger, IA

390 piston rings

Thanks for setting things straight. I had thought the rings would match the bore diameter, but when searching JEG's for new rings there were none for a 4.050" bore which certainly confused me.

Mar 30, 2001 | 11:12 AM

buzzard

Logistics Pro

Joined: Oct 2000

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From: All over Texas

390 piston rings

Matt, DF is absolutely correct about the bore diameter of a STOCK 390. Most of these old motors have been bored at one time or another so make sure you know what you have before ordering any parts. If your motor has been bored, the tops of the pistons should have something like .030, .040, etc stamped on them.