98 V70R Piston ring dimensions

Anarchist · Post by **Anarchist** » 14 Jul 2014, 02:21

Hello everyone,

I was hoping that someone could tell me what the dimensions of the standard piston rings are - especially the radial thickness or radial depth.

The OEM part number is 31330721 (made by Mahle pn# 038 24 N0).

I know the STD bore is 81mm and the top ring thickness is 1.50mm, second ring thickness 1.75mm and the oil ring is 3.00 mm. The OEM top ring is moly coated (as opposed to chrome or plain iron).

As a secondary question - on the Hastings rings website - does anyone know what the numbers in the brackets mean next to the ring thickness? For example, Part Number 2M4541 (the apparent correct set for the B5234T6) it says 1.50 (335). What is the (335) referring to??

Thanks in advance,
Peter

Anarchist · Post by **Anarchist** » 15 Jul 2014, 02:00

So, with the help of a friendly engine parts shop (that actually had what I needed!!!) I have some data. The ring dimensions are the same as an VW/Audi 2.2Lt 5 cyl engine also.

There is some confusion out there as some of the B5234 family use a 1.2mm thick top compression ring (newer), some use a 1.5 mm thick ring (older).

The Mahle (OEM) ring set (PN# 038 24 N0, Volvo #31330721) has a compression ring that is 3.20mm in radial thickness.
The Hastings set that they list for the B5234T (PN#2M4541) has a top compression ring with radial thickness of 3.48mm.

I'm going to take a guess and say that the Hastings set "should" work, but I will certainly measure the ring land depth in the pistons to be sure. Finding the ring land depth on the OEM piston is... well... a challenge.

Has anyone measured the depth of the STD OEM Piston compression ring landing? I'm hoping for 3.50mm or more

I hope that this information is useful to someone out there!

Anarchist · Post by **Anarchist** » 17 Jul 2014, 22:43

In the interests of completion, I have had confirmation from the good folks at Hastings* that the top compression ring has a radial depth/thickness of 0.135' + / - 0.008" (which to metric users is 3.429mm +/- 0.2mm).

The piston this was designed from has a groove depth of 0.165" (4.191mm).

As far as I can tell the Hastings set should work just fine.

The Total Seal ring set (part number CR1454) has a radial thickness of 0.135" also. Both the Hastings and Total Seal kits have moly compression rings (like the Mahle). Hastings do make a compatible chrome ring set also.

As to why the Mahle rings have a smaller radial thickness is beyond me. Perhaps the engineers among us can chime in.

As a side note the B5234T6 engine uses "sputtered" big end bearings. Glyco make a set that have this coating on them. Another potentially viable alternative to OEM...

* = I am really pleased with the service I got from Hastings in answering my questions. They were right on the ball. I hope this information is helpful to people in the future. There are alternatives to OEM ($$$) rings and engine bearings!