Ignition Timing

[december2021]

I have a question about the ignition timing on my '78 MGB.  There were a number of modifications when I purchased it a few years ago. It has a Pertronix flame thrower distributor and coil.  I followed your recommendation for setting the timing at 32 BTDC at 4000 rpm's. 

The timing at idle (900-1000 rpm's) is about 20 BTDC.  Is that about right, or have I missed something? Thanks. 
Louis Assemes

[JohnTwist]

That idle advance is OK as long as the idle is disconnected.  If you have 20 BTDC mechanical and connect the vacuum it probably moves up to about 40 BTDC?  That’s my experience.  The engine loves to idle with fast timing, but as soon as you step on the throttle the vacuum is lost and the timing reverts to mechanical. 

SAFETY FAST!

John H Twist
University Motors Online
100 East Beltline Avenue SE
Grand Rapids MI 49506-2410
Cell  616 307 6737
www.universitymotorsltd.com