Rick, if your vacuum retard is not getting vacuum due to a leak, then
the idle speed will be higher since the spec is 4 deg ATDC at idle with
the vacuum advance connected. So the spark will advance about 14 deg
when you remove vacuum from the retard unit at idle. When you reconnect
the vacuum line the retard unit will retard to 4 deg ATDC if there are
no vac leaks. I found that a lot of the little elbows dry out and don't
make a good seal over time with the plastic tubing, so by timing with
the vacuum line to the retard plugged I am getting better performance
while under way instead of when idling. I usually tune my car to 10-12
deg BTDC with the vacuum line to the retard unit plugged.
If you fix the leak, then reconecting the retard unit should bring down
the idle if the retard unit is not leaking. I usually time the engine
with the vacuum line plugged and the idle as low as possible so the
mechanical advance is not working. With the vacuum line plugged, I'll
turn both carb screws CCW in equal amounts to get the idle as low as
possible without stalling, time the engine, then put both screws back to
where they were after I reconnect the vacuum line to the retard unit.
Of course you may need to adjust the carb balance and overall idle
anyway if you had to turn the distributor.
But if the vac retard is not working, you can continue to run the car by
simply checking your timing per the above method with the retard line
plugged, time it to 10 deg BTDC, then simply adjust the idle to the
proper RPM. However, eventually you may need the retard unit to pass
emissions.
Good luck
John - 76 TR6
Rick wrote:>>
I have been unsuccessful in getting the idle speed on my '75 below
1100rpm or so. The consistent advice is to deal with everything else,
including vacuum leaks, before adjusting the carbs. While I really
thought I had the the vacuum issue dealt with, I discovered last eveing
that I did not.
The litle elbow connector at the vacuum advance is cracked all the way
through on its underside so I asume it is leaking. But what bothers me
is that plugging the vacuum port on the manifold does not change the
engine idle. Shouldn't there be some change in the idle when blocking
that port?
The engine runs very well other than the fast idle.
Would advanced initial timing increase idle speed and not otherwise
degrade performance?
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