Which rings do I need

[Trimster]

Ok, engine apart and here's the tail of the tape...
cyl size top size bottom
1     --3.017   3.025
2     --3.013   3.012
3     --3.017   3.028
4     --3.017   3.030

piston size is 3.011
Stock cyl. size should be 3.0122
Tolerance according to the manual .0015 over then rebore is needed to accept next oversized piston.

Appears to be some taper, but not a whole lot. What do I need for rings? I would love to just hone, re-ring and put it back together if possible.

[jtanguay]

which engine? 1.6 N/A?

[Trimster]

Sorry. Yep. 1.6na

[jtanguay]

check for ovaling of the cylinders.  measure the side to side at the top and at the bottom and then measure the front to back of the block top and bottom.  that will help determine whether the rings can seal properly.

http://www.vwdieselparts.com/rebuildi.htm

that site should have all you need

[Doug]

Are you sure about your measurements? That defies conventional wisdom. If you have as much as 13 thousandths diameter taper between top and bottom, I would say that it is time to go oversize. Why don't you check those bores again using a ring end gap as a reference. Then use the formula C=PI D to calculate the diameters of the bores again top and bottom. I would think that with the measurements that you have now you must be into some serious oil consumption as well as piston slap. Remember to take your top measurement below the top reach of the rings in the bore. That is within the swept path of the piston rings.

[Trimster]

I'm not satisfied w/my measuring skills. Only had a short time to use an inside feeler and mic.  The piston to wall gap is a tight .005 on all but #2 which is a tight .004. Measurements taken mid stroke.

All the dia. measurements were within the stroke range.  I'm in search of a true bore gauge tomorrow. Going to hit the pawn shops. No one here rents them.

Yes the engine was using oil... a qt./500 miles. Blown head gasket as well. It's looking like it's on the edge of boring out (which would be the right way to do this) and oversized rings.
here's #2 piston...

No scoring on the cyl. walls. In fact, the crosshatch is still there in places. Found the guy who rebuilt the engine just 7000 miles ago. New rings, bearings, gaskets. No mention of boring.
Thoughts are welcome.

[Doug]

As I wrote before "Why don't you check those bores again using a ring end gap as a reference. Then use the formula C=PI D to calculate the diameters of the bores again top and bottom." Save your time with the shops, unless that is what you want to do. This is an accurate method to get the diameter measuement at different stations within the bore, Remember to measure the thrust surfaces of the bore. Place an unbroken piston ring from one of your pistons squarely in the bore measuring the ring end gap. Then calculate.

Is there a signifigant step at the top of the bores after the carbon has been scraped away? If not, then possibly the rings that were installed before did not seat properly because of poor honing technique or tools. Check the ring side clearance in the piston lands. If it is acceptable within or very close to limits then you may well have success with new rings only. The amount of land wear is very important as the rings have to be held squarely to the bore for them to seat. Without seating, you will always consume oil. Check your valves and gudes especially if it is a high miler engine as any signifigant wear can cause oil loss to exhuast and intake. I once did a valve guide/and new valves only on a 1.6 Rabbit which lowered the oil consumption by about 400-500 miles per litre bringing it up to around 1200 miles/litre or so which was acceptable. The rings were not touched.