Fw: <VV> 140 pinging

[larry at forman.net]

Here are some ideas to try:
1. Check at how much vacuum the vacuum advance arm starts moving and 
adjusting the timing.  It should not start pulling until about 8 or 9 
inches of vacuum.   My guess is it starts before 5, as nearly every one 
I have ever looked at has weakened internal springs.  So the 
"adjustment" is to remove the vacuum advance can, place it on the open 
jaws of a vice (two bricks can work in a pinch) and take 5/8 inch and 
9/16 inch deep sockets and deepen the depression around the vacuum 
nipple about 1/16 inch or so.   Check with a MightyVac or other vacuum 
source with a vacuum gauge to see when you pound on the surface and 
compress the spring.  Do the adjustment slowly checking as you go.  
This will reduce the onset of vacuum advance and might help you.  
Reinstall the vacuum advance can and go for a run to see if the pinging 
is gone.

2. Really should have been #1, check the cylinder compression and make 
sure the engine is in good shape.  Also perform a tune-up with new 
plugs, wires, air cleaners, etc.  I like Bosch 7502 aka W8AC Super 
Copper plugs.  Gap at stock gap for starters.  No amount of carb or 
distributor adjustment can compensate for a tired engine, bad plug 
wires, etc.

3. Check that your accelerator pumps are working properly.  Often the 
cups are heat set and don't pump well or much at all.  You can also 
drill a hole 1/2 inch inboard on the accelerator pump lever arms on 
both primary carbs to improve the response of the accelerator pump 
action.  You will need to cross drill the linkage to install a very 
small cotter key since the normal linkage clip will not work unless you 
shorten the arm to match the location of the new hole.  Leaving the arm 
the stock length you can always move the linkage back to the original 
location if desired.  Some people drill up to three holes at various 
distances inboard of the stock location to provide several adjustments 
from normal to really hot accelerator pump action.  

HTH,
Larry

----Original Message----
From: Pitts10ch at aol.com
Date: May 9, 2007 14:59 
To: <virtualvairs at corvair.org>
Subj: &lt;VV&gt; 140 pinging

By the way, original distributor never been messed with except new  
points.  
33,000 original miles total.  I guess springs could be  played.  I 
guess one 
has to interpolate readings higher than 16.   Thanks.
 
CH