The main issue with installing the Dale vacuum advance/retard unit on a turbo is the following:

If you set the timing at 24 BTDC with the vacuum hose disconnected and plugged, when you hook the vacuum hose back up your timing will be around 34 BTDC.  At wide open throttle (WOT) you will still have proper timing, but your idle quality may be poor.  You may also experience some off-idle stumble and hesitation when the timing drops 10 degrees or so as you let out the clutch and start to move off the line.

If you set the timing to 24 BTDC with the vacuum hose connected and your timing at 24 BTDC, you will have improper timing especially during WOT (about 10 degrees short).  At idle your timing will be at 24 BTDC, but as soon as you let out the clutch and start off the line your timing will drop to approximately 14 degrees.  Moving a stock Corvair turbo off the line is not the time when you want to retard your ignition timing from the factory setting of 24 BTDC.  The low compression ratio coupled with the comparatively poor throttle response of this engine begs for all the ignition lead it can get at that time. 

This electronic device, used in conjunction with a vacuum solenoid* will allow the Dale Vacuum Advance/Retard units to function properly at all RPMs.  The electronic control circuit monitors engine RPM and sends a signal to the vacuum solenoid.  The vacuum solenoid can then properly control the stock manifold vacuum signal to the Advance/Retard units depending on engine RPM.  

* You will need to obtain a vacuum solenoid for this part to function properly.  Vacuum solenoids are very common on any late model vehicle. These are easily obtainable at salvage yards.  Any vacuum solenoid will work for this application.  You only need one inlet and one outlet port, but if the vacuum solenoid which you find has other ports, these can be easily blocked off.

If you need assistance in locating a suitable part, just let me know.  Click here to send a note