Piston Ring Tolerances
Thread Starter
Intermediate
Joined: Mar 2022
Posts: 33
Likes: 1
Piston Ring Tolerances
I started doing a refresh on the 350 in my 1973 Corvette. I got the pistons out and honed the cylinders with a ball/ flex hone. Each cylinder was oiled with 10-30 and honed for around 20 seconds. To my knowledge, nothing has been done to the bores, and the pistons look stock. I ordered rings for a standard 4.00 in bore, and when I went to start fitting the rings, straight out of the box, the top ring was at .020, which, from my understanding, is about .004 too large. I did it on all the pistons, and they all had the same measurement. +/- 0.001. Can I use .01 oversized rings and grind them to the correct clearance with the stock pistons?
Race Director
Joined: Nov 2006
Posts: 13,227
Likes: 7,823
From: Sunshine Coast, Queensland, Australia
2025 C3 of the Year Finalist - Modified
2024 C3 of the Year Finalist- Modified
2022 C3 of the Year Finalist - Modified
Cruise-In VIII Veteran
With the old style rings . The standard was always. 004 per inch. Or about 16 for a 4 inch bore.
keeping in mind that would be the MINIMUM spec. On a brand new engine. On this engine 20 thou sounds just fine.
I would run them as is.
If I was gapping new rings for a new engine at that bore size using old fashioned rings I would be shooting for .018 - .020.
I never gap at absolute minimum.
keeping in mind that would be the MINIMUM spec. On a brand new engine. On this engine 20 thou sounds just fine.
I would run them as is.
If I was gapping new rings for a new engine at that bore size using old fashioned rings I would be shooting for .018 - .020.
I never gap at absolute minimum.
Thread Starter
Intermediate
Joined: Mar 2022
Posts: 33
Likes: 1
With the old style rings . The standard was always. 004 per inch. Or about 16 for a 4 inch bore.
keeping in mind that would be the MINIMUM spec. On a brand new engine. On this engine 20 thou sounds just fine.
I would run them as is.
If I was gapping new rings for a new engine at that bore size using old fashioned rings I would be shooting for .018 - .020.
I never gap at absolute minimum.
keeping in mind that would be the MINIMUM spec. On a brand new engine. On this engine 20 thou sounds just fine.
I would run them as is.
If I was gapping new rings for a new engine at that bore size using old fashioned rings I would be shooting for .018 - .020.
I never gap at absolute minimum.
Last edited by Logan B; Jun 13, 2025 at 01:04 PM.
