AeroNed at aol.com
AeroNed at aol.com
Thu Nov 25 16:06:04 EST 2010
Happy Thanksgiving! and thanks for the tips.
I am going to be rebuilding the engine at a machine shop. Anyone remember
Glen Ziesenis? Well, I'll be at his shop. I'm planning to rebore the
cylinders and he has the fixture to do that under compression. I'll also be
rebuilding the head and doing a valve job.
I'm still curious about doing a re-ring job. Maybe I need to find a good
engine and experiment.
I've rebuilt engines before, even a couple Corvairs. The last time I
rebuilt the rods and did a valve job at Glen's shop. Both firsts for me. This
time will be the first rebore for me. I'm hoping to keep the compression down
so I can still use unleaded and not generate too much heat when running
In a message dated 11/25/2010 9:01:16 A.M. Central Standard Time,
djtcz at comcast.net writes:
----- Original Message -----
Date: Wed, 24 Nov 2010 19:39:06 EST
From: AeroNed at aol.com
Subject: <VV> Re-ringing
My winter project is going to be the rebuilding of a 95 hp engine to go in
my 65 coupe. This engine will be hooked to a PG and will be running AC.
"core" engine is a runner that smoked when removed. I'm thinking it may
only need rings (and new bearings and other while I'm there parts).
Anyhow, I've heard all sorts of stories about re-ringing a Corvair engine,
most of them bad. I'd like to hear some of the good ones. I really would
like to keep the bore stock. What are the "tricks" I'll need to know to do
The back of the Corvair shop manual has a "Specification" section. On the
one or two engine pages there are some key dimensions that must be within
service limits to achieve decent performance and life.
An area that may be easy to overlook is how much clearance the new rings
have in the used pistons (or even new ones). Check with a feeler gage.
Don't blast piston ring grooves clean with any abrasive, since the rings
must seal against the groove walls, and the groove's finish and form can be
destroyed by blasting. Cleaning carbon from the grooves grooves with a
broken ring can do some damage too.
ANy ridge worn at the top of the cylinder must be removed to keep the top
ring from jamming in the "corner" right at TDC. Every Cylinder's roundness
and taper needs to be measured and evaluated honestly. Surface finish is
important, but there is a range of acceptable roughnesses. Inadequate
cylinder cleaning will tear up new rings quickly, and I suspect may be behind many
of the "darned rings didn't seat" stories. A few squirts of carb cleaner
is not good enough. One good test is An oiled white rag must stay clean
after being scrubbed against the "cleaned" cylinder wall.
During end gap checking I like to put each new ring in the cylinder, near
the top of it's travel, square it off by inserting a flat topped piston,
and backlight the ring with a flashlight and look for light at the cylinder
wall. Visible light indicates cylinder ovality beyond the ring's
capabilities to conform. Or maybe tweaked rings. End gap needs to be checked where it
is tightest, in the smallest portion of the bore, usually near BDC. In the
quest for tight end gaps some folks start with an oversize ring. That is
probably OK, as long as when finished the ring passes the back light test.
Oil Smoke can originate from valve stem, guide, and seal issues, as well
as crankcase ventilation problems too.
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