Problem Installing Oil Rings
Thread Starter
Instructor
Joined: Aug 2005
Posts: 182
Likes: 9
From: British Columbia
Problem Installing Oil Rings
I'm having a problem fitting the oil ring stack into my forged pop-ups that I am reusing on my 331 freshening up project.
The rings fit fine on the even cylinders but the grooves on the odd numbered bank are too narrow to install the 2 rails and expander. First off, I thought I had a ring set with a manufacturing problem, but I've now tried 2 sets from 2 different manufactures, Sealed Power and Hastings with the same problem.
I Measured the oil ring grooves on the even bank they're at .1875 which seems correct but the odd number bank I come up with .008 smaller and therefore the ring stack won't install. Seems to be a variance with the pistons.
I see on the ring manufacture's websites that they offer oil ring rails thinner than what was provided in my box(s) of rings. I've never came across this before as a "hobbyist". I'm thinking that the .1875 piston groove width is nominal and what I need to do is order some thinner rails to suit the pistons in question.
My question to the more experienced engine builders is, am I on the right track here? Order the thinner rails? I really don't want to change or cut pistons. I wish I would have kept the old rings to compare....
The rings fit fine on the even cylinders but the grooves on the odd numbered bank are too narrow to install the 2 rails and expander. First off, I thought I had a ring set with a manufacturing problem, but I've now tried 2 sets from 2 different manufactures, Sealed Power and Hastings with the same problem.
I Measured the oil ring grooves on the even bank they're at .1875 which seems correct but the odd number bank I come up with .008 smaller and therefore the ring stack won't install. Seems to be a variance with the pistons.
I see on the ring manufacture's websites that they offer oil ring rails thinner than what was provided in my box(s) of rings. I've never came across this before as a "hobbyist". I'm thinking that the .1875 piston groove width is nominal and what I need to do is order some thinner rails to suit the pistons in question.
My question to the more experienced engine builders is, am I on the right track here? Order the thinner rails? I really don't want to change or cut pistons. I wish I would have kept the old rings to compare....
Race Director
Joined: Jan 2002
Posts: 15,355
Likes: 2,726
From: Close to DC
C2 of the Year Finalist - Modified 2020
I'm no machinist, but if you have 8 pistons and 4 of them measure different in the oil ring groove, then something might be wrong with the pistons. As a second thought, 4 of them must weigh differently then the other 4 and this would cause, I believe a balance problem. You might want to talk to the machine shop or someone who sold you the pistons and or did the machine work. 
Dennis
Dennis
Le Mans Master
Joined: Nov 2003
Posts: 5,772
Likes: 694
From: Maryland
St. Jude Donor '05, '09, '15
Sounds like a piston issue not a ring issue. I have never heard of a set of pistons having different size ring groves. I'd contact the piston manufacturer and get the proper ring grove dimension and start from there but sounds to me like you are gonna need some machining at minimum. 
Race Director
Joined: Mar 2009
Posts: 19,777
Likes: 4,592
From: Canada's capital
2020 Corvette of the Year Finalist (appearance mods)
C1 of Year Finalist (appearance mods) 2019
They used to make a reamer to clean out the grooves in used pistons that would might work for you. It's a hand operated little gadget.
Le Mans Master
Joined: Nov 2008
Posts: 5,691
Likes: 12
From: columbus oh
this sounds like a mis-match of pistons to me , i wonder if the part numbers are the same???
oh well,,,interesting stuff......good luck to the op......
Thread Starter
Instructor
Joined: Aug 2005
Posts: 182
Likes: 9
From: British Columbia
Well I feel like a bit of an idiot and now I know I need glasses for sure. It was traces of carbon causing the rails to hang up. It doesn't take much of that stuff to make up a few thousandths here and there. I was ready to junk the pistons (L2166NF).
As a side note the nice lady at Hastings told me there should be .002 -.007 clearance between the rails/ lands or 25ft/lbs max lateral resistance. 25ft/lbs seems tight but I'm at 2 -3 thousandths so I'm a happy camper.
As a side note the nice lady at Hastings told me there should be .002 -.007 clearance between the rails/ lands or 25ft/lbs max lateral resistance. 25ft/lbs seems tight but I'm at 2 -3 thousandths so I'm a happy camper.
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