[T3] On a 73 T-3 SB fuel injected aut trans pinging .
jadney at vwtype3.org
Tue Dec 5 21:58:29 PST 2017
On 5 Dec 2017 at 18:44, William J wrote:
> The Bently state to set the timing to have the lines off and plugged and
> only states the engine RPM at 850 idle . Is this correct? And if so when you
> raise it back to 950 plus or - 50 RPM this may advance the timing a bit. for an
> auto matic car. What is the best way?
It's always a problem if the distributor is already started up the
advance curve at idle. This leads to the vicious cycle I mentioned
earlier. You might want to try lowering the idle speed slowly while
watching the timing to see where the advance starts. For the AT AH,
it should start somewhere above 1000 rpm. So timing at 950 should be
fine. Note that since there's no advance between 850 and 950 for the
AT AH distributor, either speed should give you the same correct
But, if you find that your advance is starting below 1000 rpm, you
might try swapping the springs, just in case they got swapped before.
If that doesn't fix it, you're looking for someone with a distributor
As for the springs, one will be snug when stationary and that one
will hold the advance to zero until its preload is met, then it
controls the early, low rpm, advance.
The other spring has an elongated loop so it doesn't come into play
until some higher rpm, then it stops the advance until the
centrifugal force also overcomes that spring's preload; that gives
the flat section of the advance curve.
Once the second spring's preload is met, the advance continues, but
now the advance curve is less steep, because the centrifugal force is
working against the combined strength of both springs.
One other thing to check is to look at the 2 arms that got adjusted
at the factory to set the advance curve. Look for any signs of
damage, because sometimes someone loses the screw that holds the
little plate that holds the points connector to the outside of the
distributor. If they replace that screw with something longer, it can
reach in and bend those arms when the distributor turns. That
completely destroys the advance curve calibration.
Hint: Any time you've done distributor work, always spin the
distributor shaft by hand before reinstalling it. If there's an
interference problem, it's MUCH better to discover it by hand, before
you let the engine force it around.
Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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