<VV> Re: sleeved valve guides, and bronze

[N. Joseph Potts]

I'd like to reqest some basic education, here. What is the idea of
installing bronze sleeves in valve guides?
     Is a bronze lining supposed to be superior to a "bare" guide?
     Is a new guide either so expensive or so difficult to install that
relining is cost-effective?

     Answer to questions about the remains of mine: the guide appears merely
to have cracked and broken - from what remains I see no obvious signs of
overheating, nor other indications that the guide was subjected to any
unusual or violent forces. These findings survive also an inspection of the
valve, which seems totally intact. One way I'm pretty sure the seat didn't
come out is that the top of the piston does not show any impression of the
valve (smile).

Joe Potts
Miami, Florida USA
1966 Corsa coupe 140hp 4-speed with A/C

-----Original Message-----
From: virtualvairs-admin@corvair.org
[mailto:virtualvairs-admin@corvair.org]On Behalf Of djtcz@comcast.net
Sent: Sunday, August 15, 2004 11:31 AM
To: virtualvairs@corvair.org
Subject: <VV> Re: sleeved valve guides, and bronze


>> From: "N. Joseph Potts"
> I pulled the head off.
> The VALVE GUIDE on that intake valve, which had been resleeved > >with
bronze, had broken, evidently near the end that's in the >combustion
chamber.  I am missing that inch, more or less, from that >end of the guide
(which  pulled out of the head by hand). This head had >been professionally
refurbished in May 2003, and installed in February >2004. Less than 5,000
miles. Teflon valve-stem seals were installed >then.
Are the inserts thin wall sleeves, or the spiral inserts (like a bronze
helicoil) ?  How much wall thickness is left after machining for bronze?
What color is the OD and ends of the loose guide?  Discolored from heat?
The OD is probably nasty from moving around in the now-buggered-up head
hole.

First I would question the installation of the bronze inserts, in regards to
the remaining guide wall thickness.  The inserts I am aware of are swaged or
burnished after installation by forcing an oversize tool down the ID to
tighten them in the guide bore, but before the bores are reamed/honed to
size .  If the remaining guide wall is "thin", it would be EASY for the
swaging operator to crack the portion of the iron guide not supported by
head material and maybe not even know it. I'd look carefully at the
surviving guides with a bright light and a magnifying glass. If they look OK
I  might even go to a welding supply shop and get  Spot-check dye penetrant
kit.  My paranoia would force me to pull the other head to inspect its
guides.
--------------
Whether the guide integrity is good or bad I'd investigate the
valve-to-guide clearance. Note the 1965 manual specifies 0.0010 new minimum
on the intakes, and 0.0014 new minimum on the exhaust, with no difference
for the reported bronze guides in the Turbo engine. 0.002 inch is solidly in
the middle of the new spec.  I'd like to think one benefit of synthetic oils
is they will maintain valve stem clearance much better than dino oils.