300tdi ring gap positions

[Gumnut]

Hi,

After many trials, deprevations and tribulations, I have finally started to re assemble my engine.

After reading Haynes and OEM Manual, there appears to be a few contradictions and/or missing information.

Can anyone provide a definite and correct indication of the positions of the ring gaps on the pistons on a 300tdi?

And, whilst I am on a roll, the correct side for the bearing tags on the big ends.

At least the pistons have an arrow on them, and hopefully it does not point to the rear of the engine when viewed from underneath at night in the rain, or some other equally obscure description...........

[BigJon]

As far as ring gaps go, as far apart as possible. Just make sure they are not lined up.

[langy]

When I gave my 300tdi a new set of rings and a headgasket, a tip on the new rings packaging indicated 120 degrees from each other ( ie 12-4-8 o'clock positions). The bigger worry was getting all the carbon out of the ring guides without taking metal off, and installing the rings without breaking them. I invested in a decent ring expander, and it all went well. As for the tangs on the big ends, I had marked them prior to removal and now don't recall, but there is an illustration in RAVE overhaul that shows tangs same side together. Just watch the threads when putting the pistons in. A bigger tip is making sure the block and face of the head are spotless and surgically clean. I used thinners to finish the job and hylomar on the gasket as well. Last, when torquing up the head - use a checklist and paint pens to indicate which bolt has been staged to which position. It can get confusing.

Otherwise it's easy - I did it and my Disco is still going strong almost 100k later.

[BigJon]

a tip on the new rings packaging indicated 120 degrees from each other
The bigger worry was getting all the carbon out of the ring guides
and installing the rings without breaking them.
Just watch the threads when putting the pistons in.

As far away from each other as possible...
I usually break an old ring and use it as a scraper.
Very carefully!!
Slide a couple of pieces of rubber hose over the exposed big end bolt threads. That will protect the crank and the threads.

[Gumnut]

Thankyou so far.

I am fitting new pistons etc, and have been caught out before with bolts and crankshafts.......

I believe the gaps should be on the non-thrust side, and staggered.

In plain terms, camshaft side or other side?

And same for bearing tangs. I can't bring myself to put them back the way they were, which was two one way, and two the other.......

There was no correlation between wear and direction, as the whole job was pretty much stuft, and definitely in need of a rebore.

[Blknight.aus]

assuming you have the 3 piece oil scraper ring

I assemble the 3 piece oil scraper ring so that the 2 splits in the edge rings are on the non thrust side of the piston,120 degrees apart and not lined up with the gudgeon I then position the split of the spacer is between the 2.

for the 2 compression rings I set them up so that they are on the non thrust side and again 120 degrees apart but not lining up with the gudgeon.

If you have the single piece oil control ring then I aim to have the the split of that and second compression rings on the thrust side but 120 degrees apart and then the top compression ring on the non thrust side again with no ring gap over the gudgeon.

the most important guidelines for ring positioning being

1. no ring gap should fall in the thrust area of the cylinder (which is usually a sweep of about 100 degrees)
2. no ring gaps should overlap unless there is an intervening ring.