63 Avanti R 1

[avantinet]

I have a question on timing. Does anyone have an idea as to why the timing settings on the engine would change as much as 4 or 5 degrees on it's own? It seems to take about 300 to 400 miles after the timings been set.

[Gunslinger]

Did you just install new points? It's not unusual for points to need to be reset after being installed and they do have an initial break-in period with some cars. The first few hundred miles the rubbing block on points wear at a faster rate than the next 10k miles. Once they break-in the wear rate decreases. With dual points the chances of this are even greater.

Other causes...points may have slipped due to hold down screw not being tightened properly, the distributor hold down bolt being loose, allowing distributor to rotate slightly, in a non-Stude engine I would say timing belt could have slack but Stude engines have gears, not belts...very unlikely for that to be the problem. The Prestolite distributor in an Avanti is known for having the bushings wear with age...that can cause timing problems.

Timing is a function of dwell and distributor positioning. If they change the timing changes. Look to the distributor for your problem.

[avantinet]

Thanks for the help. We will check all the possible culprits.

Edited October 19, 2010 by avantinet

[ernier]

Check that the breaker plate isn't sticking. The vacuum advance changes the timing by moving the breaker plate. If the plate is not free to return to its original position or if you set the timing while the breaker plate was stuck it will change everytime you drive the car, literally. Advance weights sticking or a rotor loose on the shaft could also give you erratic readings.

Gunslinger is right, start at the distributor it's in there somewhere.