<VV> My Wonky Spyder

[Lonny Clark]

Do a compression check.

It could still be a valve seat at fault, adjusting the valve lash may not
tell you.

Lonny Clark


On Thu, Sep 16, 2021 at 12:12 PM Jim via VirtualVairs <
virtualvairs at corvair.org> wrote:

> I need some help diagnosing a miss on my '64 Spyder.  Last weekend, I drove
> about 45 minutes to a meeting place for several other members of our local
> CORSA chapter before we left as a group to go to an classic car night at a
> marina on Lake Ontario.  The temperature was in the mid-70s, and it was
> sunny; i.e. a beautiful day for a convertible.
>
> For about half an hour, my drive was at expressway speeds of about 55-60
> MPH.  The last 15 minutes was in residential/commercial areas at 35-40 MPH.
> When I arrived at the meeting spot, I was the first, so I let the car idle
> for a few minutes before turning it off and opening the engine compartment
> to let the engine cool.
>
> The other members arrived in about 15 minutes so we left.  As I started the
> Spyder it, immediately it had a bad miss.  I thought it might be carbon [or
> something] and left with the others.  After driving for about 10 minutes,
> the car wasn't running any better, so I turned around and drove home.  No
> idiot lights came on, head temperature was normal, no unusual engine noise,
> but there was a slight flutter in the boost gauge.  Uh, oh.  My drive home
> was without incident except that the engine was down on power [no surprise]
> and it sounded like a WRX with it's lumpy exhaust note.  It seems to be the
> exhaust valves because there is no backfiring through the carb.
>
> After arriving home, I set the carb to a fast idle to keep it running,
> pulled the spark plug wires off, one by one at the distributor and found
> that #3 and #5 made no difference in the engine idle.  There was a strong
> spark from the distributor contact to the plug wire contact.  I left it
> alone to cool and later changed those spark plugs to see if they had become
> fouled.  No difference.  I connected a separate vacuum gauge to the  line
> to
> the distributor and the flutter while running was very apparent with the
> gauge diagnosis label indicating valves.
>
> Today, thinking that maybe the valve seats dropped, I took off the valve
> cover and turned the engine over by hand, following the procedure in the
> '61
> shop manual for adjusting the valve lash cold and checked #3 and #5.
> Nothing appeared to be out of the ordinary:  No loose rocker arms or
> pushrods or a valve obviously stuck open.  Going back to the ignition, I
> replaced the spark plug wires for #3 and #5 with new ones just to confirm
> that it wasn't ignition, and it wasn't.  I had a Corsa with a 140 that
> dropped a seat, and it was obvious when I removed the valve cover and saw
> the loose rocker arm.
>
> So now, I'm at a loss for the cause of the miss.  Did I overlook checking
> anything?  Does anyone have any other ideas of what the cause might be?
> Could it be two burned exhaust valves that suddenly both began to leak?
> [That would seem to be a pretty wild coincidence.  Would they both leak
> suddenly?  I would think that a burned valve would be a gradual thing.  But
> hey; what do I know?  I'm only an amateur at this.]
>
> I'd appreciate any thoughts or suggestions.
>
> Jim Bartasevich
>
>
>
> This is one of the disadvantages of wine:  it makes a man mistake words for
> thought. - Samuel Johnson
>
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