31 Jul
2001
31 Jul
'01
3:17 a.m.
Douglas Quebbeman wrote (re Vegas):
The original process was supposed to put a layer of
something
other than aluminum on the inside of the cylinder walls... I
want to say silicon, but that can't be right...
You're close! In fact the Chilton book for the Vega discussed the
process for doing so in the field after honing the cylinders. In
essence you took a chunk of Teflon (available under a GM part number),
chucked it into a drill and used it to polish the cylinder walls.
The Vega (1970 -- or was it 71? Motor Trend "Car of the Year") was
supposed to have Detroit's first rotary engine. When they couldn't
figure out the apex seal problem they tossed that 2.3L thing
into the car.
I've always asserted that the Vega engine looked like a project
done by a bunch of new grads -- it had all sorts of nifty
textbook ideas that don't work terribly well in the field assembled
in one place:
- A sleeveless aluminum block. Great idea on engines designed to
run for one race, awful for a street car.
- "Bathtub" block cooling rather than lots of cooling passages.
Rather than a big hunk of metal with water jackets around the
cylinders, the Vega block is essentially a rectangular tub.
Cylinders one and four are attached to the front and back
ends of the block, while two and three are siamesed together
and rise out of the bottom of the block like the Hawaiian
islands from the Pacific. Coolant fills the rest of the void.
The notion here was that you eliminate metal (hence weight)
and simplify the casting process. The problem is that with
limited cooling between two and three those two cylinders tended
to "sink" back towards the bottom of the block. Again, great
for a race car, awful for a street car.
- A cast iron head. I'm not sure who thought that the combination of
a cast iron head and an aluminum block was a good idea, but
between the difference in thermal expansion rates and the tendency
for cylinders two and three to "sink", Vegas blew a lot of head
gaskets. Enough so that a special replacement gasket appeared on
the aftermarket that was thicker around numbers two and three.
- An overhead cam that directly drove onto cam followers that didn't
need shims. Great idea; no longer do you have to remove the
camshaft in order to set the valve lash. Stick a hex wrench in
a hole on the side of the follower and turn, just don't turn too
far because we forgot to put a stop on it and you can send the
adjuster out the other side of the follower, where it will jam the
follower in the "down" position the first time the cam hits it.
- A rubber timing belt that was tensioned by the water pump. The
precursor of the serpentine belt that plagues -er- more
contemporary vehicles.
- The "vacuum leak center". The Vega appeared at the beginning of
the 70's, a period wherein, rather than addressing the underlying
issue of meeting emissions by making engines run right, Detroit
applied a series of kludges, almost always in the form of assorted
and sundry vacuum delay valves and vacuum motors. The result was
a generation of induction systems that could do parlor tricks with
exhaust gas but didn't have a clue when it came to a cup of high-test,
and as implemented on the Vega came in the form of a collection of
valves and hoses that invariably leaked under transient and
difficult to reproduce conditions.
All in all, it really was a _terrible_ piece of engineering.
--
Chris Kennedy
chris(a)mainecoon.com
http://www.mainecoon.com
PGP fingerprint: 4E99 10B6 7253 B048 6685 6CBC 55E1 20A3 108D AB97