[SCG] 1964 Decklid update

Mon Oct 31 14:32:42 EST 2005

Since we have no memo from Fisher Body or GM R&D or Engineering to point us
to why the change happened or exactly when it was to be implemented in
stamping operations, we are all in the same boat in determing the exact
when and the why. But I would not be so quick to dismiss the thought that I
provided as any estimation by any of us should be considered as to the when
and the why the holes vary in number if there can be some sensical things
that can be pointed to.

Some things to consider that does make sense when considering the
possibility of why the rear oval stampings were reduced:

1. Airflow was determined back then at GM in a room with wind directed at
the front of the car to simulate forward motion of the car. This was done
with strategically placed drops of ink to trace wind flow. There is a photo
of this in one of the historical Corvair books as an early model is being
tested.

2. There is some downward force of air at the tail of the car. As it forces
it way down to the deck lid, air is pushed to the louvered holes in the
deck lid, and some finds it way thorugh the decklid, but is substantially
helped to be drawn in down to the engine shroud components by the suction
created by the fan atop the engine.

3. Air is also carried past the car due to the forces created at the front
of the car. This builds speed of the air flow and pressure. Speed of air
flow is also increased when the area/hole the air is being forced through
is reduced. Much like if you have a light 5-10 MPH  breeze in NYC Central
Park or another more open area. If you are walking on the sidewalks you
will find that you will encounter "gusts" of wind at a far higher speed
than the breeze you felt in the open, hitting you as you walk past the
areas between the buildings. Air needs to move and when being squeezed
between tight spaces, it increases speed, pressure and creates some draw
from the primary air source behind the lead forward motion. Just physics
here.

4. The more gaps you have, the more air you stand to lose in an "enclosed"
system.. The decklid on the early is NOT completely closed. The top and
bottom stampings, although welded at the edges, is not welded or glued
around the area where the air is drawn in through the lid. There is a
fairly large open area that works all the way back to the oval holes on the
back edge in question. Air can easily be allowed to travel right from the
louvered area to the oval holes at the back of the deck lid.  It would be
incorrect to think that ALL the critical air being passed in through the
louvers and further drawn in through the fan to the engine makes it to the
intended destination just by virtue of how the decklid is constructed. All
the other perforations in the bottom stamping lead down to the engine
compartment. All except the holes at the rear edge of the deck lid. They
are over the top edge of the rear panel, outside the engine compartment and
outside the rear edge weatherstrip seal. This can drain water and drain
air, especially when the car is in forward motion.

Consideration of the above and a good look of how the deck lid stampings
are put together should be taken into view, abscent of any memo for Fisher
or GM.

Rich

             "Bill Hubbell"                                                
             <whubbell at cox.net                                             
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                                       [SCG] 1964 Decklid update           

             10/30/2005 11:58                                              
             PM                                                            

             Please respond to                                             
               Bill Hubbell                                                
             <whubbell at umich.e                                             
                    du>                                                    

Rich Thompson brought up a question about 1964 engine Deck Lids having to
do
with a mid-year change in the underside venting.  I think I can narrow down
the date of change to late March, 1964

My 1964 Ember Red Sedan (40960W22477    WR15189) has a build date of 03C.
It has the eight oval drain holes found on all earlier models.  However, it
also has the extra holes for the longer rear weatherstrip.

Smitty's 1964 Daytona Blue Spyder Convertible (40667W?????  WR3709) has a
build date of 03D.  It has the 2 oval drain holes and 6 "pads".

So at the present time, it looks like there were 3 different versions of
1964 Deck lids, with the third version appearing near the end of March.  We
obviously should get more cars to confirm this date.

As for the reason for this changeover, I haven't a clue.  I don't think
Rich's assumption that it had something to do with cooling makes any sense,
as the engine fan draws air into the engine compartment and it wouldn't
make
any difference how many drain holes are in the lid.

Bill Hubbell
SCG President

> One change though, of note that I have seen with '64 deck lids: there was
> some sort of change made with '64 deck lids in the underside venting.
> Somewhere between late November 1963 and early April 1964 cars, the eight
> ovals holes found on the underside of the rear edge of the deck lid (four
> of each found on the right and left of the deck lid spring) were changed
> to
> only have two (one only to the right and left of the spring). My Spyder
(a
> late November car) has all eight holes. My sedan, a early April car, has
> only two and my 500 coupe (a late week of July/last week of '64 model
> production) also has two holes (the stamping for the eight holes are
still
> their, just not pierced through on six of them). This is an assumption on
> my part, but the eight holes might have been their to provide adequate
> draining of water through the deck lid to prevent rusting on the inside.
> But, (this presented as a possibility) it was also found that the eight
> holes let too much cool air out of the top access vents of the deck lid
> engine cooling, robbing the engine of some much needed air. Maybe that is
> why it was switched to two holes to reduce cool air loss. Any other '64
> owners see similar difference in holes in the deck lid?
>
> Rich
> SCG Historian

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