<VV> My Wonky Spyder

[Matt]

Check the manifold at the pass. Side head…common for the bolts to loosen / threads strip

Matt Nall
Sea Mountain
SW  Oregon Coast


Sent from Mail for Windows 11

From: Jim via VirtualVairs
Sent: Thursday, September 16, 2021 12:12 PM
To: virtualvairs at corvair.org
Subject: <VV> My Wonky Spyder

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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