<VV> Fw: bronze valve guides

[Mark Durham]

Brad, suprisingly, both Clarks catalogs and the GM manual for my 62 are
devoid of that information. GM's notion was to leave the guide in place and
ream it oversize and get valves with oversized stems to match. 40 some years
later, we are changing the guides.

However, the stock guide O.D. is .517", from clarks pg 20.
Clarks says that if you try to drive a too oversize guide in, you may have
to ream the hole to original dimensions. Ask whomever you bought the parts
from, they should know.

Maybe there is someone out there who has done enough heads to know the
measurement.

On the question about using a stem seal on the bronze guide, Clarks sells
both styles. If you read the OTTO section on their Manganese bronze guides,
they basically say to NOT use the stem seal, but to do a better job of
setting the valve stem to guide clearance to get some lubrication, but not
too much.
Team that with the tufftrided valves, which help to hold lubrication in
place, they say you could get 100K out of a valve job.

They also say that adding the seal excludes lubrication to the valve and
advances wear. Which makes sense.

How long do typical factory type valve jobs last with seals? A good question
I cannot answer. I do know that years ago, i overhauled my corvair engine at
80K miles because the cam gear lost its teeth, and at 80K I needed to do a
valve job (the car was running great but the clearances were at the outer
new limits). But I reamed the guides and bought o/s stem valves with seals.
After that, I ran the car another 80K miles and sold it, so I don't know how
long it ran after that.

So, there are two ways to go. The std approach will give you satisfactory
performance for a long time with a good oil. The OTTO guides would give you
more than satisfactory performance for a longer period of time with a good
oil (The tighter clearances ensures the valve stays truer to the seat for a
longer period of time which means it will seat better longer.   Your choice.
If you really want to do something good for the valves, ensure you set up
the push rod geometry correctly. The std rocker puts a slight side load on
the valve stem each time it pushes down and makes it wear the guide in a
elongated oval pattern, and this is worse when the rocker is not properly
centered on the valve stem.
Or, you could install roller rockers!

Mark Durham

On Sun, Dec 6, 2009 at 11:44 AM, Brad Hall <rbh3794 at yahoo.ca> wrote:

>
>
> --- On Sat, 12/5/09, Brad Hall <rbh3794 at yahoo.ca> wrote:
>
>
> From: Brad Hall <rbh3794 at yahoo.ca>
> Subject: bronze valve guides
> To: virtualvairs-request at corvair.org
> Received: Saturday, December 5, 2009, 8:34 AM
>
>
>
>
>
>
>
> Can anyone out there tell me the correct intake bronze valve guide
> interference in a corvair head?  Should I use intake valve stem seals on a
> bronze guide?
>
> Thanks for all of your technical help.
>
> Brad Hall
> Corsa Ontario
>
>
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