308 GT4 second set of points

They retard the idle timing by 10 crankshaft degrees -- mostly an emission thing, but it also gives the benefit of increasing the airflow in each carb to achieve the 1000 RPM idle speed which makes the idle more stable (i.e., the idle RPM is less sensitive to subtle unrepeatability in the idle position of the throttle plates).

Because they can't deal with the added complexity There is zero performance gained by removing them.

 

At Carl Rose's site:

https://ferrari.cdyn.com/

https://ferrari.cdyn.com/ferrari_docs/308gt4_workshop.pdf

What year/version 308GT4? A US version would be set to 3 deg ATDC on the R2 points (see Section O) and the S159B distributor adds a lot of advance as RPM increases. A euro version would be set to 6 deg BTDC on the R2 points (see Section L) and the S159A distributor adds much less advance as RPM increases

 

Steve's description is a good one. I worked a LOT on 308's years ago, and found that the cars certainly ran better with both sets of points in and correctly timed. I've kept my original sun Distributor machine, which i found to be a great tool to set these distributors up in.

I'm only chiming in because I'm pretty sure I have TWO GT-4 factory workshop manuals. One of which is an original somewhat tattered, and the other is a complete copy of one. I probably also have quite a bit of factory documentation on these cars. I'm pretty sure the owners manuals also cover the setting of the ignition quite well also.