<VV> ignition/carb advise needed

[BobHelt at aol.com]

Hi Devin,
Please see comments below.
Regards,
Bob Helt
 
In a message dated 9/9/2006 1:59:34 PM US Mountain Standard Time,  
devin at valleyautomotivesupply.com writes:

I've  been chasing a stumble in my wife's 63 for a while now and am nearing 
my wit's  end.  Hopefully somebody out there will have some thoughts on the  
matter.

The problem:  At 1200-1800 rpm (approx, no tach) the  engine will stumble so 
bad it will buck the whole car.  This is at light  throttle cruising.  It is 
worst when the engine is cold, but it still  happens to a lesser degree when 
the engine is warm. 
 
Is there any way you can isolate this to carbs or ignition? My experience  is 
that short periods of a dead engine are due to electrical problems. Carb  
problems usually last longer. And I'm assuming that this stumble is only for a  
short time period. Have you checked to see if any electrical units quit at the  
same time? Radio? Headlights?
 
1200-1800 rpm translates to about 25-40 mph in 4th. If that's where you are  
getting the stumble, what happens at the 70 mph your drive on the freeway?



What I have done:  
Carbs:  Checked choke linkage,  works freely.  Set idle mixture to highest 
rpm.  
Ignition:   Checked timing.  14 degrees initial.  Checked against factory  
manual, calls for 32 degrees total, including vacuum advance.  Vacuum  advance 
is not hooked up, checked it recently and it does not work.   Advanced total 
timing to 32 degrees.  This made the stumble nearly  disappear for a few days, 
then it returned.  Put timing back down to 14  initial.  
 
Something's not right here. First, total timing is without the VA unit, not  
with it. Next, total timing is 37 deg, not 32. But that is at 4800 rpm. Are 
you  revving to 4800 to measure the total? Timing is good at 13-14 deg. Why not  
install a working VA unit? That will help your gas mileage. That's what it is 
 for!
 
 
 
 
 
 
Pulled cap and inspected.  Found some corrosion on the inside of the  cap.  
Cleaned this off.  Removed, cleaned and inspected the  points.  They were 
pitted some, filed them and re-installed.  Now when  I set the points to .016 gap, 
factory spec, used, I have 45-48 degrees of dwell,  instead of 31-34 degrees 
it calls for. 
 
 
Seems strange.Why not open the gap to 0.019 and check dwell. Is the dwell  
steady?
 
 
 I have not yet pulled and inspected the plugs.  A full tune-up  was done 
about 2 years ago, about 8k miles back.  Cap, rotor, points,  condensor, wires, 
plugs and air filters were replaced and carbs were  rebuilt.

By the way, this is a 102 HP engine and 4 speed trans.  I  drive it to work a 
few days a week, 40 miles round trip, 18 miles in each  direction freeway at 
70-75 mph.  Doing this I'm getting 20 mpg.  I  would think I should be doing 
better than that.
 
 
Maybe it's just me, but in all these years of driving  Corvairs, I've never 
gotten over 22 mpg and usually 16 around town and 20 on the  highway. So in my 
opinion, you are right in the stadium (used to be ballpark--  haha)
Regards,
Bob Helt

Devin