<VV> Banging Noise from Engine - Update

[Jim]

Thanks to everyone who sent me suggestions about things to check that could
have possibly caused this noise in a '66 110/PG car.  We had checked almost
all of the items you suggested before receiving your posts but still could
not find the source.  Here's a summary of what was done to solve the
problem:
 
When we took the head off on June 16, we didn't see anything unusual.  The
bang seemed to be coming from the driver's side of the car.  We took the #4
piston/cylinder off because the cylinder seemed to be "dead" when checking
the spark but didn't see anything unusual there either.  
The first time I heard it was on June 11 after one of our members who was
working on the brakes of the car called me about it when he and the owner
started the car.  I made a visit, and the owner started the engine while the
other member and I stood at the back of the car.  I had a hunch that it
might be from the area of the torque converter [TC] from where I was
squatting down beside the driver side rear wheel, but I didn't follow up on
it because I had never heard such a sound before!  Had I done it, that would
have saved us all the effort of removing the head and cylinder.  [Live and
learn!]
 
Because we still didn't know the cause, I went back myself on the 23rd to
follow-up on my hunch and had the owner rotate the engine with a wrench
while I looked in the cooling air exhaust hole on the lower passenger side
of the bell housing.  There it was:  One of the three bolts that hold the
torque converter to the flex plate was missing.  Then I took off the front
shroud where the PG dipstick and throttle rod enter the engine compartment
to get access to the torque converter bolt access plate.  The bolt was not
missing but was loose!  See the attached photos while looking at them in
order. 
 
Note that in photo 4 there are multiple holes drilled through the bell
housing to make a large hole just above the opening where the TC bolts are
installed and tightened.  Also note that in photo 3 there is no clip holding
the nut in place on the TC like in the other photos.  It was held on with an
adhesive.  Apparently, the assembler of the power train made the hole to
allow wrench access to the TC nut when tightening the bolt because the clip
was missing.
 
After notifying everyone who was working on the car of my findings, the
member who called me initially said that he used Loc-tite on the TC bolt and
reinstalled it.  He also checked the torque of the other two TC bolts.  It's
interesting that Chevy didn't use any lock nuts, washers, or something like
Loc-tite on the original bolts.  
 
The engine was reassembled and no more banging.
 
The moral:  Follow your hunches and try the easy fixes first!
 
Jim Bartasevich
ACORN, Rochester, NY
 
 
Get your facts first and then you can distort 'em as you please. - Mark
Twain
 
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