> I've got a '68 1600 that I dropped a U20 which was smog equipped. Since I
> removed the pump and all the other smog equipment, I realize now that the
> vacuum lines will be routed differently...
Okay, I'll try to not sound preachy... :-)
When you yanked the smog stuff, did you replace/recurve the
distributor as well?
The emissions equipment all works together. Yanking one piece
without taking all the other pieces into account can do unexpected
(read: bad) things. Luckily, on our little Roadsters there's not a
lot of pieces but I've seen so many cars brought to their knees
'cause "all this smog stuff's gettin' in the way"... Okay, that was
getting preachy...
Pre-68, the distributors had an initial advance of 16 degrees BTDC
and a total initial+mechanical of 31 degrees. '68 onwards used
a different curve and was set initial at zero degrees and full advance
of 35 degrees. That zero degrees initial made the car a pretty poor
off-the-line performer.
The TVS (thermo vacuum switch) is used to advance the curve
when the engine gets too hot. It's a safety device. Past a certain
coolant temp, it switches the feed to the distributor from the carb
port to straight manifold vacuum, advancing the timing, speeding
up the engine, and forestalling a meltdown.
Therefore, you do not want to yank the TVS unless you are also
recurving the distributor. The TVS isn't creating poor performance,
the smog-curved distributor is.
Things to note:
1) Solex cars don't have vacuum advance.
2) If you set a 'smog' distributor at 16 degrees advance the engine
will run much better at idle and risk melting a piston at WOT. In
other words, don't.
3) Along with the smog pump (air injection system), the mixture
was richened up a bit. This provided fuel to burn in the exhaust
manifold.
4) Those injector nozzles are NOT standard pipe threads. Close,
but not quite. Using hardware-store plugs will rip up the aluminum
head.
5) Using plugs on a U20 creates an annoying birdlike 'chirping'
every time you get off the gas. Rallye used to make a special
two-piece plug. Tom Walter used to machine a spiffy proper-shape
screw-in plug. I don't know who may have a good solution at present.
6) What curve do you have? This is stamped on the weights, which
can be viewed/serviced by carefully removing the breaker plate.
The number stamped there '7.5' or '17.5', is CAM advance - double
for crank advance. 7.5 is 15 degrees mechanical advance (pre-68, set
initial to 16) and 17.5 is 35 degrees, set initial to zero.
-- John
John F Sandhoff sandhoff@csus.edu Sacramento, CA
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