A few points to consider :
Opening the throttle destroys vacuum advance.
Twin carbs dumping a load of petrol means that petrol will take longer to burn. Hence more advance will be needed. This is achieved with mechanical advance with less need for vacuum advance.
I'd love to know why Volvo recommend ATF Type A (one of the older, thicker ATFs) to damp the dashpots and stop them going crazy.
Pinking is also known as pre-ignition meaning the inlet charge has already burned before TDC has been reached. If the timing is too far advanced to start with, poor cold starting will result. That means it's important to get the balance right between having enough advance while running and not so much advance at idle. Too little advance at idle can also result in flooding a cold engine with the choke and lack-lustre performance.
There's a lot to be taken into consideration with timing. Way back when, i ran a modified Cavalier 2.0 and the standard timing mark was at 5 deg BTDC. Through trial and error, i found it not only idled best at 11 deg BTDC but also performed best on the road, not just in terms of power and economy but drivability as well.
For various reasons i lost access to the timing light with advance settings built in so i went and paid a garage to do it. This was allegedly a garage that did rolling road tuning so should have had a vested interest in getting it right. I explained in detail what i needed and why. They gave me the car back and it didn't sound right. It didn't go right either!
I ended up swinging the dizzy round myself and timed it by ear. With hindsight i should have done that myself in the first place and saved my money.
After that i made up a protractor and marked the correct timing for the engine on the crank pulley. Just for reference, that car was running a 38DGAS and not the original Varajet-II carb. It also had a hot cam in and a few other mods and was capable of blowing the doors off a dark blue 3.0 Senator much to the annoyance of the officers inside it! They goaded me into giving it some beans and then had the cheek to take me to court for speeding!
