Timing

[Doug&Deb]

Recently I recall reading something on this forum about checking timing by engine vacuum. I can’t remember what thread I saw it on. Am I correct about this? If so I’m curious as to the procedure. I’m intrigued.

[greg g]

Locate a intake manifold vacuum port.  I use the wiper motor feed.  Connect the gauge. Loosen the dist clamp so you can rotate the distributor  but not so loose that it won't hold position where you set it.  Start the car and run it up to normal operating temp. With idle speed at 500 rpm or so

. Rotate the distributor  to achieve the highest reading that still holds a steady needle. Normal vacuum reading should be 20 to 22 inches of mercury on the dial.  Adjust idle speed if necessary to back around 500. Now snug the distributor  hold down and go for a ride.  Find a hill and while climbing the grade accelerate from 30 to 50 in high with wide open throttle.  If you hear pinging or sparkknock, retard the timing until the ping goes away.  This might take two or three times up the hill.  Once the ping is gone, tighten the dist, adjust the idle as needed. While the gauge is attached, you can also use the gauge to set the idle  mix  by turning the screw to again get the highest steady needle reading.

 

Note that to do this test you need to start with a steady vacuum reading.  If your needle is bouncing around or waving at you you need to address those things as setting the timing won't be a valid procedure.

 

In the downloads section of this site is a chart on how to read and interpret th e various vacuum gauge readings.  Check that out before grabbing your tools.

Edited September 7, 2021 by greg g

[chrysler1941]

Greg g beat me to it

 

 

Edited September 7, 2021 by chrysler1941

[Doug&Deb]

Thanks, I’ll check it out