I removed the distributor. The other bolt was also in the fully advanced position. I made an adjustment and also inserted the distributor one tooth advanced. Now my engine is idling nicely with 6 degrees timing at 750 rpm in neutral and 650 in gear.
Having two adjustment bolts complicated things for me.
You can change that and find the clamp that they used on the later slants into the 80s. It allows basically infinite adjustment similar to a small block. They are kinda hard to find, though.
