2G Piston very tight in cylinder after new piston rings

[96dsmftw]

I just reringed my pistons and gapped them correctly. The 2 oil rail scrapers seemed like they would never compress close to the piston. All of the bags that had the ring sets in them say 3.346 so I know I ordered the right ones anyways. I put the first one and it went in tight and it is really hard to move up and down. I can get it to move but only with the end of a mallet and a good hit. I made sure the ring compressor was on the block while I was tapping them in as well. I feel like it shouldnt have been as hard as it was. There are no scoring marks from a ring scraping the block either. So I took it back out because I didn't like the fit, and I had to force it out. The rings look fine they were not bent or messed up. No scoring on the walls from the ends of the rings or anything. I am confused now because if all 4 go in like that I don't think the starter could move it when I do get it back together. It has taken off some of the hone job where it was so tight. Everything I have seen in videos they like plop in and just a light tap can move them down. I was looking at the oil ring again this is what I saw. The oil rail scrapers are pushing in on the wavy ring so hard it left impressions on the piston. I rotated a bit so you can see the indentations on the piston. Anyone have an idea what is going on???Help please and thanks. Oh and got Manley rings, box says part number 46850-4.

 

[OGDSM1989]

are you setting the gap ? ....

 

[MyKey J Orlando Jr]

Did you disconnect the connecting rod from the crank? If so it might be your bearings. Other wise it might be a dirty side wall after the honing did you spray it with carb and choke cleaner then lube it?

 

[96dsmftw]

I set the gap on the 2 top rings. The oil ring gaps don't get set they just have to be above a certain spec I believe. The piston is not connected to the crank. I didn't even take it down far enough to get it close to the crank because it was so tight. The cylinder walls are clean. Sprayed with brake cleaner and then wiped down until the white microfiber towel stayed white.

 

[MyKey J Orlando Jr]

Call the ring company and the piston company to check file gap specs. I file gapiled my wisecos with a die grinder and they came out perfect. Maby they weren't compressed right

 

[OGDSM1989]

Well brake cleaner is just that a cleaner, never have I used brake / carb cleaners when building a motor other then to clean it. When setting my rings and pistons. I would try using a WD-40 or equivelent which are lubricants I have even wiped the wall down with a light weight oil such as 0-20 and then wiped that clean with a WD-40 just to pre lube the walls etc .... Honestly though it sounds as if your ring gap is off .... you set the ring in about 1-1.5 in from top of cylinder leveled it by flipping piston over with no rings and slid into cylinder, measured ring with feeler gauge.

Standard value
no1 .25-.40mm (.0098-.0157 in )
no2 .45-.60mm (.0177-.0236 in )
oil .20-.70mm (.0079-.0276 in)

Limit
no1 .800mm (.031in )
no2 same as above
oil 1.00mm (.039in)


are the piston and rings new or old piston and new rings? These values may change a little by manufacture and type of ring but as I follow the service manual I usually (Knock on wood no motor failure) I have good results.

 

[96dsmftw]

I used some new non synthetic oil to lube the cylinders before I put them in. I just used the brake cleaner to clean after the hone. And yes, I gapped the rings like you said. I pushed them down with a piston that had a ring on it so I knew it was flat too. And they are new Manley rings gapped to 0.020 on top and 0.023 on bottom. I checked the oil rings too and they were like 0.018 or so.

 

[OGDSM1989]

all those are are tight according to Factory service manual when they expand you will have interference .... not to be a stickler but I use a median of all

no1 0.32-0.35
no2 0.52-0.55
oil 0.45-0.50

I would go back re gap them would hate to have that be the issue or cause another issue later under boost. These Motor are not really designed to have super tight tolerances ..( in my opinion)

 

[96dsmftw]

I was talking in inches and I think you are in mm. The Manley spec sheet I found online said 0.007in for every in of bore (for running medium boost 15-30psi) so, 3.346x0.007 gave me 0.023in and I read most people do smaller on top than bottom so went with 0.020in (what others had done). And their spec for the oil rail says "Min 0.015"" which they were over that. Its the oil rails that are making it hard to go in. When I tighten them in the ring compressor I cant even get the compressor to touch the piston because the oil rails are pushing out so hard. The oil rings should push against the wavy rail, in towards the center of the piston, right? There is a step on top and bottom of the wavy rail that they are pushing on. They are stock pistons by the way.

 

[OGDSM1989]

when the piston are in w/out rings they fit nicely ...what is the gap between piston and cylinder wall ?

 

[96dsmftw]

I measured in between the piston and the cylinder with a feeler and got 0.003". Without the oil rails in the pistons fit exactly like I thought they should. Nice and easy to get in and move up and down nicely. So I took some measurements from the new rings and the old rings. Here is what I got:

------------------------------------------------------------------New----OLD
-------------------------------------------width of oil ring-----0.092--0.081
----------------------------------------width of wavy ring-----0.108--0.090
width of step where oil ring butts up against wavy ring.----0.039--0.029

attached are the pics of old rings vs. new
Is it possible the box for the rings say they are for standard bore (I confirmed part number on Manley website) but the oil rings are actually for 0.020 over??

 

[OGDSM1989]

okay, thats a place to start ..... rings for .20 over will be different then standard bore. You should get ahold of Manley maybe they got packaged wrong that will cause issues, explain the issue I know it maybe expensive but get a set of OEM rings and check oil rings see what it yeilds ... I believe a few possible things ... major out of round cylinder or pistons could be causing this or ring gaps ( Oil ring ) are causing some sort of binding while in the cylinder the fix will be to have the block machined and set for .20 over piston and rings ........but fore sure check w/ Manley and see what they recommend

 

[96dsmftw]

I sent Manley an e-mail but of course its Sunday and so I will have to wait until tomorrow. However, I was curious because of the dimensions of the wavy ring step and tried the stock old wavy ring with the new Manley oil rings and it went in perfect. No extra force or anything just like I thought they should. I have a feeling something is wrong with the rings I got but we will see. Could I use the old wavy ring and the new oil scraper rings since the wavy ring doesn't actually touch the cylinder? If I have to of course.

 

[OGDSM1989]

I would just grab a set of new OEM rings and use the oil ring w/ the Manley scappers .... unless your planning on building a monster motor. I had an idea last night .... messure the oil gap on the piston and then messure the overall oil ring and if the oil ring is over gap / try an get the step demension also ...

 

[96dsmftw]

Well got some news from Manley. Apparently the rings only work on their pistons. So that sucks haha. So now for some OEM replacements. However, the old rings I took out are 5 per piston. All the stock replacement stuff I see has 4 rings per piston. The pistons I've got have the stamp that belong to a 2g. What OEM replacement would have five rings per piston??