<VV> Engine issue

FrankCB at aol.com FrankCB at aol.com
Mon Nov 29 15:24:58 EST 2010

18 degrees timing advance seems rather large for a Corvair.  What does  the 
GM Corvair 1962 factory manual recommend?  If you use premium gasoline,  is 
the pinging/detonation reduced or eliminated?  Many Corvair engines  
require premium fuel even running factory settings.
Good luck and let us know what you discover.
Frank Burkhard
In a message dated 11/29/2010 2:10:09 P.M. Eastern Standard Time,  
bicknell at cfanet.com writes:

I have  recently acquired a 1962 Rampside with #2 piston burned from what
appeared  to be detonation.  All other pistons/cylinders looked normal.
After  replacing the piston and honing the cylinder to clean up the  
transfer, the same #2 piston became burned due to  detonation.  The engine
would idle fine at 14 degree timing, but with  lack of power.  At about 18
degree timing it seemed to run reasonably  and with good power, but with
pinging noticeable when starting from a dead  stop.  I have replaced the #2
piston again, this time with a different  used cylinder  and still notice 
detonation from start, but haven't  driven it much until I can learn more
about what's going  on.

When I replaced the first piston, I also changed rings and  bearings and
timed the camshaft to the crankshaft as accurately as I could  determine.
This seemed to be a challenge.  I used keyway positions  checking with
machine squares.  Since such advanced distributor timing  is required, I am
still wondering if this is an issue.  What is the  best technique for this
timing operation?  But why did the same  cylinder position have the problem 

I have  been rebuilding conventional water-cooled engines for decades, for a
while  professionally, so I know engine basics but something is eluding  me
here.  Perhaps something unique to Corvairs.  Knowing  that
pre-ignition/detonation can initiate from carbon build up and/or  sharp
edges, I wire brushed all combustion areas, valves, and valve  cavities
clean prior to assembly.  All fins were cleaned to avoid hot  spots.  The
sheet metal air deflectors are in place.  The  thermostat properly opens the
air deflector valve when the engine heats  up.

Can someone help with some suggestions?

Bill  Bicknell


Cell phone:  970-218-1352

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