| [ Total Views: 564 | Total Replies: 6 | Thread Id: 103158 ] |
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 JacksonAndDad
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| posted on August 20th, 2013 at 03:46 PM |
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Oil scraper rings gap
Hi,
Before I get to the question a quick history:
I have just dismantled the motor from my 74 1800cc bus to replace the seals etc as its a bit leaky. I compression tested before removal and had
128-135 psi in the cylinders. Once apart all the tolerences (big end, little end, mains, pots diameter, piston skirt etc) are below max
tolerence.............except the oil scraper rings! the compression rings have a .4mm end gap (book says .5mm max) but the oil scrapers are 1.2mm to
1.35mm (book says .4mm max). Now im left scratching my head because if the motor was worn out and things measured poorly I wouldnt be surprised with
the huge oil ring gap, but because everything is in good order I am shocked at the oil ring gap
Has anybody come across this before?? Has anyone put a new set of rings in an 1800cc lately and measured the oil ring gap and found they have
increased the end gap or something?!?!
Thanks in advance,
Tim
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AA003
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| posted on August 20th, 2013 at 05:03 PM |
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Many years ago I had oil rings wear out long before the compression rings.
I read it on samba, so it must be correct.
Sometimes Volkswagen dealers sell spare parts. Amazing isn't it!
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 vw54
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| posted on August 20th, 2013 at 05:44 PM |
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If you have it apart replace the rings but get the cylinders honed
Might not be a bad idea to do the valve guides as well if the heads are not cracked which will be a surprise
hows the cam and lifters there always worn
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JacksonAndDad
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| posted on August 20th, 2013 at 06:17 PM |
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Thanks AA003
vw54 - The cam has very light wear on the sides of the lobes but not on the peak of the lobe, the cam shells are in excellent condition and the cam
bearing surface is .05mm below new spec. The heads must of been replaced recently as they are in excellent condition, the seats are not pitted and the
guides appear to be very good. I have polished the seats and valves.
I called Mick Motors today and asked for an opinion on the excessive oil scraper gap....the fella said he has not rebuilt anything but he would
replace the rings
Well if this is not a 'new' design thing with the large oil scraper gap I will get a new set of rings. I will get a .1mm hone too
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dangerous
A.k.a.: Dave Butler Muffin Man
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| posted on August 21st, 2013 at 05:26 AM |
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Oil rails on modern rings have larger gaps than previous style oil rings.
(sorry no specs in front of me but the above numbers seem fine in my memory)
Yes, while it is apart, you may as well fit new ones,
but measure them, and see that they are likely quite large out of the box.
I will try to find some specs for you,
but those specs you quoted are probably from the old style 1 or two piece oil ring ,
not a modern 3piece (or 4!) with rails and expander.
Don't hone 0.1mm from your barrels.
Just measure them for round, and deglaze them if need be.
Make sure the oil ring expander does not overlap when you fit the rails.
| Quote: | Originally
posted by westi
That's mad Alan.
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dangerous
A.k.a.: Dave Butler Muffin Man
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| posted on August 21st, 2013 at 05:57 AM |
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http://www.deves.com/oilring_inst.php
Not sure I would like a 1/4" gap,
but it gives you an idea that larger gap is not so important.
"Minimum" gap however should be no less than .015" (just less than 0.4mm)
| Quote: | Originally
posted by westi
That's mad Alan.
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JacksonAndDad
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| posted on August 21st, 2013 at 06:34 AM |
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Thanks Dangerous,
The oil rings are a 3 piece set, 2 thin rings and a wave middle ring. When I was removing the oil rings I did notice that the gaps in the top and
bottom oil rings were inline with the joint in the wave ring. I did suspect that that was wrong but the large gap has thrown me
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