I have a 350 from an 88 k2500

i got new piston rings and had my block honed and cleaned my pistons real good so ive been trying to put my pistona back on but it keeps stopping at the first oil ring (the very first ring) i asked the guy at the machine shop and he said since its an 88 the oil rings may be different and if i compared them id see a big difference but i see no size difference at all which makes me think i have the right rings.

Any idea why the piston wouldnt go in yes its lubed up

 

Are you using a ring compressor?

 

Yea i first tried the band compressor. Then i tried a plier type compressor which was actually worse cause the paint chipped off and i had to take alot of time spraying that all out

 

What rings are you using?

 

Hastings 2M 139

 

I had the same problem with my motor last winter... The rings were the right part number but the oil rings & expander were the old style "wide" ring not the narrow low tension ones.

If you have your old rings still compare them.

If not then after putting on the oil ring make sure that you can push one side of the ring in the groove below the ring land. if they are the "wire" rings they will stick out from the land as they bottom out in the piston.

And yes it took me a bit to figure that out... kept looking at the part# and yep it's the right.... ones... except for the wrong ring in the right box....

 

How big of a difference is it? Cause i looked and honestly they looked the same to me

 

If they go into the grooves in the piston, it's not a "wide" vs "narrow" kinda thing.

Sounds more like you got .030" over rings and you're trying to put em into a std bore; assuming of course they're not incorrectly assembled somehow.

Try putting the rail rings into the bore without being on a piston.

 

I tested the rings and gaps back when i first got them (i dont remember the gap) they fit in the bore no trouble and i ordered standard rings. But ill check again tomorrow if i have time. I just dont get it haha

 

are you sure you have the oil ring support installed correctly?

 

It should be a tight fit really. Hard to tell over the internet in text format on how bad your rings are catching or hanging up. I know I use the wooden or plastic handle of a hammer to tap and push pistons into the bores on most all of the engines I build.

Make sure your oil ring support/expander band is not over lapping. The ends needs to butt together but not overlap.

Make sure you are using the ring compressor in the right manner. Years ago a buddy of mine was building an engine and borrowed my tapered fixed size ring compressor and called me with close to the same prob as you are having... "My pistons won't go through the compressor into the bores, what's wrong?" I get over there and he has the compressor upside down with the taper at the wrong end.

 

Yea it doesnt overlap it buts up

 

The problem I had is maybe best described as this the od of the bottom of oil ring groove was bigger than the Id of the oil ring when ring is in the bore. Because of that impossible to get piston in bore because even though the od ring is right once on piston you can't compress ring to bore size because it bottom's out in oil ring groove 1st. Hope that helps express what I was talking about with normal "wide" cross section and the low tension or larger inside diameter oil rings

 

So i should order narrow piston rings?

 

Pictures are worth a thousand words

 

What do you want a picture of

 

What daferris is talking about is more a matter of the ring groove in the piston not being deep enough for the rings, rather than the groove "width". However that would look like ring "width" being too great for groove "depth", since it's the distance across the flat surface of the ring.

DEFINITELY a possibility.

If the ring fits the bore, then ... it's the right ring for the bore. However if once it's on the piston, you can't compress it to where it's flush with the surface of the piston, then the grooves in the piston aren't deep enough for the rings, or conversely the rings are too wide for the piston groove depth, and you need either different rings, or different pistons.

It's a bit harder to check the oil rings for that because the whole expander/rings assy has to be put together and in place to measure it. Might want to check the compression rings though, and see if they have the same issue.

I seem to recall this being a thing having to do with factory pistons more or less exclusively; which I've never even tried to re-use so I can't say for sure.

 

So we just micd the new oil ring compared to the old and its just BARELY and i mean BAAARRREELLYY bigger so i guess i need to get different rings but im not sure which ones to get now