<VV> Dropped Valve Seats

[J R Read]

>From my experience - two 140's and one 110 seat, the dropped seat typically 
(physically) occurs much as Smitty described, in low stress situations and 
often after a brief stop.  Two of them were just after gas stops and one of 
those before I even got out of the driveway of the station.  In both cases 
the seat fell back into place and I was able to drive on - gently - knowing 
that I had a "loose" valve seat.

However, something had to have occurred prior to the seat actually falling 
out (fan belt? other? something before I was the owner?) which had started 
the process which lead to the actual displaced seat occurrence.  It may have 
been a one time overheat occurrence OR a series of occurrences like the up - 
down mountain scenario OR something as simple as an accumulation of heat - 
cool cycles over a number of years AND/OR other factors.  Often, you end up 
with a (smiley face?) on the top of the piston when the seat slips out but 
does not break and (at low speeds) you might detect a sound similar to a 
wedding ring falling onto concrete.

Now, they don't all (unfortunately) happen at low speed.  I had one go (# 3) 
on a 140 at approx 80mph and it took out the whole right bank.  Particles 
floated through the intake manifold in both directions and turned #s 1 and 5 
pistons and cylinders to junk as well.  I'm embarrassed to admit, but this 
came about around three months after a serious overheat situation (my fault) 
when the sun was on the dash (convert) and I neglected to notice the idiot 
light.

When inspecting a head for possible past overheat occurrences I not only 
look at the valve seat area for damage, but also look for evidence of a lip 
on the edge where the head gasket can leave an impression if the head got 
too hot in the past.

Later, JR


----- Original Message ----- 
From: "George Jones" <65crownv8 at gmail.com>
To: "Smitty" <vairologist at cox.net>
Cc: <virtualvairs at corvair.org>
Sent: Tuesday, May 08, 2012 8:13 PM
Subject: Re: <VV> Dropped Valve Seats


> And lets not forget about the '68 110 that, in May of 1988, after a
> "warm-over" rebuild and daily operation for about 3 months, dropped a 
> valve
> seat when driven for about 150 miles; stopped for lunch (a half an hour)
> and then started the car again to a loud repeated hammering sound. 
> Everyone
> said "110's don't drop valve seats". I believe I would toss that into the
> heat cycle category.
>
> George Jones

> --------------------------------
> Corvair Society of America (CORSA)  (since 1987)
> Performance Corvair Group
> Central Florida Corvair Club (Since 2009)
> Tidewater Corvair Club (since 1987)
> Central Virginia Corvair Club (since 2006)
> '65 Monza Crown V8 Convertible
> '66 Monza Coupe Custom
> '67 Monza Coupe Custom
>
>
>
> On Tue, May 8, 2012 at 11:49 AM, Smitty <vairologist at cox.net> wrote:
>
>> Smitty says;  For what it is worth I'd like to make a comment on valve
>> seats.  There may have been some that dropped valve seats after getting 
>> an
>> engine hot on the uphill and then cooling going down the other side.  I
>> know
>> of no incidents like that, first hand.  The ones I know of happened like
>> this.  1- Owner of a 140 on a warm day convertible cruise in town stopped
>> for an ice cream.  Came out and started the engine, and a seat fell out.
>>  2-
>> Car in restoration for 2 years, initially started and allowed to idle for
>> 20
>> minutes to quiet lifters.  68 95 hp.  Shortly after lifters pumped up, 
>> seat
>> fell out.  3-Restoration project engine being used to move car in and out
>> of
>> garage. 64 95 hp.  During one of maybe 10 such moves, seat fell out.
>>  4-Hard
>> working, camper hauling, Late 95 hp in flat country left idling to warm 
>> up
>> engine on a cold morning.  After 5 minutes, seat fell out.  5-Late 110hp,
>> (also a camper hauller in flat country), left idling to charge camper
>> battery.  15 minutes later a seat fell out.  6-The jury is still out on
>> this
>> one because the seat went back in the hole and the owner refuses to 
>> believe
>> there is anything wrong.  I40 hp. Car was in a parade.  Seat fell out as
>> parade was over.
>>
>> Three of those were mine.  I realize that I am only one person and am
>> limited to my knowledge of events in my 43 years of playing with 
>> Corvairs,
>> but those experiences indicate to me that most valve seats fall out at 
>> low
>> rpm and in non stressful conditions.  Not going down the back side of the
>> mountain.
>>
>> If I have to drive a car which has to be handled with kid gloves under
>> certain conditions, I don't think I will be driving it long.
>>