[v8volvo]

Bad idea to do it using the cold start.... it will make it too advanced at idle, but not advanced enough at higher RPM. The cold start advance system bumps the timing up by about .3mm (measuring pump plunger travel at Cyl #1 TDC), but is only effective up to about 2000 rpm, after which point the pump's normal centrifugal dynamic timing mechanism takes over and it reverts to the normal warm setting.

If you want to properly advance the timing..... Well, first start by removing the wire from the cold start mechanism and let it go back to doing its thing on its own. Then you will need to get a few special tools. What you need is the dial gauge and holder that screw into the back of the pump and indicate where the timing is set. Without them you will have no idea what the effects are of the changes you are making, and you run the risk of doing serious damage to the engine, especially if you're not familiar with fooling around with the timing on these things and don't yet have your ear "calibrated" to know what timing settings are OK and which ones aren't.

You can get the dial gauge and holder for a VW 4-cylinder diesel, which are cheap and very easy to find (can get a set off ebay for less than $50). Once you get this tool you will be extremely glad you have it, since you will use it many times and it will make your adjustments much, much easier and more precise. The amount of time you will waste trying to find a way to do without it will cost you way more than the price of the tools. If you want to really get serious you can get the special Volvo tool, which is like the VW one but with a longer snout on the holder so that you can use it without first removing the vacuum pump from the head..... but the Volvo one is much harder to find and more expensive, so you may find the VW one suffices. If you have trouble finding one I have an extra I can sell you cheap.

The other tools you need are a straight 19mm box-end wrench (no angle on the head -- needs to be straight) and a "sprocket buster" tool (essentially a big lever with two prongs on it to counterhold the rear cam sprocket when you loosen the bolt). The rear cam sprocket is held in position on the cam only by the torque of the rear bolt, so what you want to do is change its position in relation to the cam, so that the pump, which is driven off the back of the cam, will be slightly more advanced in relation to the rest of the motor. You'll do all this with cyl #1 at TDC (set this before you even start, to make removing the vacuum pump easier and safer), with the cold start cable tension released by rotating the interlocking halves at the cable end (also before you start), and with the dial gauge in so you can see what you are doing. Book setting value is about .85, and I think anywhere between there and about .97 is good.

HOWEVER-- all that said, if the timing on your car is already correct, you are better off leaving it alone. Can't hurt to check it but if it is within spec I wouldn't touch it. A little extra advance is OK, especially on an older, more tired engine, but as you found it really doesn't make much difference in power. Advancing it beyond where it wants to be starts to reduce power, and can cause problems with overheating, high exhaust temps, and other troublesome issues. Your real power gains will come with the turbo, not from timing.