Ignition timing

[Gaelicguy]

I’m almost embarrassed to ask this question. I’ve been building moto and car engines for more than 50 yrs. But the ignition on my Spider has me perplexed.
According to the Service Procedures:Electrical . Page 85. Ignition timing, para 3 states set the rotor towards the red mark. I’m not sure how long ago, but I’ll guess 35 yrs ago, this red mark failed to exist. In fig. 128, was the red dot at the screw at approx 7pm.position?
Also was this based on the TDC for #3 or #4 cylinder?
I’m confused
Thanks
Michael

[Dinoswede]

As far as I remember, the red mark at the distributor housing is indicating ignition point for cylinder no 1.
However, the 10 degree mark at the crankshaft pulley is for adjusting the ignition point at cylinder no 4!

This 10 degree mark can also be used checking the ignition timing for "the other pair of breaker points" -
attaching the strobe lamp to cylinder no 3.

Cylinder no 1 red mark is used only as a help in adjusting the braker points re the distributor cap contacts:
The rotor tip should always be in position directly to the distributor cap contacts, when ignition sparks are
fired. Note, at full automatic advance (at 5500 rpm:s), the ignition points are forwarded 15 distributor
shaft degrees extra!
So, the rotor tip is wide for a reason. If not, the distributor cap contacts would be burnt and/or missfiring
could develope...

Skärmbild 2025-02-10 142224.png (83.31 KiB) Viewed 6497 times

A = red mark for cylinder no 1
B = distributor cap locking pin

Dinoswede

[Gaelicguy]

Bom dia Dinoswede
Thanks for the response, the critical thing I was looking for was the location of the "red" dot. now I know where it is, there's no need for the "red dot"
Thanks again
Michael