Bill,

This mark on the distributor must not be universal, as I have at least one Volvo Bosch distributor that does not have such a mark, and one that does. (I didn't dig through all my spares/junkers, just checked the two that were handy.) FWIW, this mark is not mentioned or pictured in any of the factory shop manuals I have for various B18 and B20 engines. An aftermarket manual (Haynes) that I have for the 140 series does mention it, by way of suggesting you put such a mark on the distributor before you remove it. Bottom line - I wouldn't bet the bank on it being in the correct position.

Be that as it may, the photo below may help you sort out distributor positioning. The photo shows (with the distributor removed) the correct approximate position for the distributor drive when the #1 (front) cylinder is at TDC on the firing stroke. In the case of your B20B, the angle "A" should be at about 5 degrees. If it isn't, you can pull the shaft out and reposition it on a different tooth. You'll want to note the "depth" of the drive in the block before you pull it out, as a check to make sure you're engaged in the lube pump at the other end when you reinstall. You may need to use a long flat blade screwdriver to rotate the lube pump a little (or a lot, depending) in order to let the drive shaft engage the pump in the new position.

When this is all done on a B20B/E, the dist rotor should literally be pointing at the #1 spark plug, give or take a little... in other words, the tip of the rotor will typically be at about the 9:30 or 10:00 o'clock position on the distributor with the #1 cylinder at TDC firing.

And BTW, I don't think it was specifically mentioned in any of the responses here, but when the marks on the timing gears are lined up, it is the #4 cylinder that is at TDC firing, not #1... your gears were installed correctly.

Gary L
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1971 142E ITB racer, 1973 1800ES, 2002 S60 T5