After a nearly 5 year hiatus (hurt shoulder, Esther's accident, and millions
of acre-feet of water under the bridge) grandson Ben and I resumed assembly
of the engine I started to build up for the yellow peril. Right after I got
back to the US and set up my father's lathe in my garage (with some innovative
wiring to get the required 240v power to it) I decided my first lathe project
would be the OEM-type Volvo ring compressor, which has no moving parts. It is
a sleeve with a tapered bore, with the small end the same size as the cylinder
bore (3.5004" in the case of the B20 and B30), about 2" tall and starting out
about ¼" bigger at the top. The lathe was not bolted down to the floor and
had a bad belt(which would have required complete disassembly of the lathe's
headstock to replace) so with the jerkiness and vibration, machining quality
was not good. Since that was done in late 1998, it took me a while to find
the cotton picker in my culch heap, but we finally turned it up. I did not
have a good internal mike to check the cylinder size very accurately so I tried
it with much fear and trembling last week. I was frankly amazed at how well it
worked! I would say if you can find a piece of steel big enough and you are
planning to assemble one engine or more with the same bore, this is something
you ought to do. I've installed a lot of pistons with various kinds of ring
compressors and this one was so much easier than anything else I have used
that the time machining it was really time well spent.

The green Volvo manuals show this item in use in the engine assembly section,
at least some of them do. I used a hammer handle to push the piston into
the bore and could not tell when the piston rings passed from the compressor
into the cylinder, it was that smewth!

Naturally if you are dealing with overbores, you'll need one for each size,
but this block apparently only had about 150,000 miles on it and cylinder
size was around 3.503, so I didn't go to oversize, just had it honed clean and
true. Ring end gap still fine.
--
George Downs, Bartlesville, Oklahoma, Central US