Oil scraper rings gap

26 posts · joined Apr 2012 · 20 Aug 2013, 3:46 pm

#967041

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

AA003 Custom Title Time!

1,189 posts · joined Oct 2011 · 20 Aug 2013, 5:03 pm

#967043

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!😂

vw54 Administrator Always Waiting 4 Friday

16,723 posts · joined Aug 2002 · 20 Aug 2013, 5:44 pm

#967044

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

I read it on FACEBOOK so it must be true

http://forums.aussieveedubbers.com/viewtopic.php?tid=91278&page=1#pid848630

http://forums.aussieveedubbers.com/viewtopic.php?tid=63561&page=1#pid624099

http://forums.aussieveedubbers.com/viewtopic.php?tid=4832&page=1#pid452603

http://forums.aussieveedubbers.com/viewtopic.php?tid=60650&page=1#pid574409

JacksonAndDad Casual Dubber

26 posts · joined Apr 2012 · 20 Aug 2013, 6:17 pm

#967047

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

dangerous 23 Windows of Awesome

5,901 posts · joined Jan 2005 · 21 Aug 2013, 5:26 am

#967100

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.

westi wrote:That's mad Alan.

dangerous 23 Windows of Awesome

5,901 posts · joined Jan 2005 · 21 Aug 2013, 5:57 am

#967102

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)

westi wrote:That's mad Alan.

JacksonAndDad Casual Dubber

26 posts · joined Apr 2012 · 21 Aug 2013, 6:34 am

#967105

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