thumper64

I bought some RS Machines pistons for a rebuild and they sent 81mm rings and I bought 82mm pistons. This isn't going to work, is it?

NAH2B

nope

mar778c

iTrader: (1)

RS machines sends out the same ring package with all sizes of their pistons. It makes for some "odd" gaps but they will work very well. If you are really hung up about your gaps you can order new compression rings from hastings.

NAH2B

i think someone may have lied to you haha

mar778c

iTrader: (1)

Lol, sarcasm is a bit hard to get over the webz.

But seriously, the last three rs machine builds had ring packages which were labelled 81.00 1.0 1.2 2.8 for a 81.5, 81.5, and 82 mm builds.

NAH2B

not sure what you mean, but the rings
have to match the piston size. even .5mm difference wont work.

op, send em back, get the correct rings

mar778c

iTrader: (1)

Randy,

Normally, I would agree with that statement especially on a forged piston but you are wrong on this. I have assembled several of this motors and I spoken with RS and Hastings prior to assembly of the 1st RS build. You should call RS and then Hastings and you get the same information given to me.

What I highlighted in bold on my previous post is the ring package numbers. That package is sent with all of the 81 to 82 mm piston kits.

NAH2B

so the rings are made oversize and you file them to spec for the piston you are using? what about tension from sticking a larger ring in a smaller bore? the ring wont seat against the cylinder wall completely all the way around, it will lift in spots around the cylinder.

im not sure about rs because i have never used them, but if this is what they recomend i will never try them in the future.

mar778c

iTrader: (1)

^^^If we were talking about a forged piston, yeah I would agree with that arguement. The thermal expansion is a lot higher.

In this case, the results speak for themselves. Like I said, I've assembled several of these 1.8L engines and they all make pretty good power. I can speak from personal long term experience on one those builds. My motor has seen more than 30K miles as a DD and ~ 50 dyno pulls as a test mule. There is thread with RS builds where people are posting results.

NAH2B

yeah but the composition of the piston has nothing to do w/ the way the ring sits against the cylinder wall.

if you squeeze an 82mm ring into an 81mm bore it wont sit flat against the wall all the way around. this is the case for ANY brand ring.

it will contact the wall in some spots and not in others.

it would be difficult to tell on the dyno and im not sure about long term effects, but i know its not good.

i dont know everything there is to know about rings, but i was faced w/ the situation of running .5mm larger rings than my pistons and bore. i spoke w/ several engine builders and even spoke to a ring manufacturer (which there are only a couple) before making my decision not to run them.

everyone i spoke to told me the same thing, the larger ring wont contact the wall all the way around the cylinder because it wasnt designed for that bore size. there is more tension on the ring than should be and will wear the cylinder faster than normal but only in spots making the cylinder out of round.

i also learned that there are only a couple ring manufacturers in the world. the piston companies make their pistons to match the offered rings for the most part.

now some piston companies like CP will take someones rings and add their own touches to them such as machining them so they are perfectly flat which most rings arent from the manufacturer.

idk about rs but i wouldt squeeze a larger ring into my cylinders, thats just me.

mar778c

iTrader: (1)

You are not accounting for other forces acting on the ring that cause it to have to conform to the shape of the bore. The ring rides in groove and is forced outward due to cylinder pressure ie tension in the ring. Further, this forces must be balanced against the thrust induce forces.

thumper64

...I'm not trying to stick like 84mm rings into an 82mm bore. I am just curious if the 81s come large enough where they will have the correct gap in a 1mm larger bore.

JDMCRX

iTrader: (2)

Interesting post would like to hear more about this.

NAH2B

why dont you check them and see?

your sticking a smaller ring into a larger bore, its not gonna have the correct amount of ring tension to properly seal the cylinder. sure it may work, but its not 100%

besides if its a true 81mm ring your gaps wont be anywhere near spec. but check them and get back to us....

92cxturbo

you'll have to measure the gap and find out. I had a set for 81.50mm bore and the top and second ring gap came out the same. I cant remember what it was but it was the service limit of the second ring gap and way over on the top.

BigBlock22

but wouldnt a 1mm smaller ring than the piston have a too tight of a fit? i could understand the concept of using a .5 or 1mm larger set of rings than the pistons because you might be able to file them down... but dont really understand how you would go about the oil control rings though. mar778c where you using stock cylinders when you manipulated that setup?

BigBlock22

by too tight i meant too tight around the piston. if hes using cast pistons wouldnt there be a slight gap between the rings and cylinders?

thumper64

Too large of rings for the cylinders will end up out of round since they won't contact correctly.
Too small of rings will have too little spring tension.

Hastings doesn't appear to make 82mm rings. Who else makes good rings that will fit?

NAH2B

which is probably why rs does this. hastings is usually what you will get when you buy off the shelf je's or other cheaper brand pistons. hastings rings are cheap.

rs probably decided to use their rings before realizing they didnt offer the proper size for that particular piston. too late now haha

i used to have a catalog of rings/sizes directly from the ring manufacturers. it had every ring in exsistance listed, but i nolonger have it.

i would give race engineering a call, they can help you. depending on the groove size cp may have something for you?

Garage 808 Hatch

Hastings makes 82mm rings, we bought some last week

raiden571

uhh, i have had 3 sets and all used different sets of rings.. you my friend either got screwed or are just wrong

mar778c

iTrader: (1)

Only one of those was a hasting ring package because they only make 1 type.

thumper64

Where? I looked on their site and they don't have them the correct size for OEM pistons. The thicknesses have to be 1.0, 1.2, 2.8 for the top, second and 3rd rings.

mar778c

iTrader: (1)

Honestly, you will be fine with the package you have. I have built several of these motors with that ring package and they all make very good power. Like I said the gaps are a little odd but I've got many dyno pulls and many miles on my personal motor with no issues.

road.head

just add a little fluxcore to it. It'll fix the gap