[v8volvo]

First guess would be the valve cover gasket leaking from the front where it goes over the cam bearing cap. Sometimes can leak from the corners. and run down the front of the head behind the belt.

The cam and/or crank shaft seals could be the source of the leak but it's pretty rare, seems like they more or less only fail as a result of incorrect installation/damage, almost never while in normal operation. A blocked crankcase vent system could cause a failure but that is not an issue these engines tend to experience, the CCV system tends to be trouble-free.

Failed oil pump gasket is known to be possible, ngoma and I repaired one which was labor-intensive. Also an uncommon issue, though, and we believed that one probably also occurred due to a damaged gasket on that engine which had been taken apart before, rather than a "natural" age/usage failure. This one is a massive and continuous leak if it occurs since the oil is under pump pressure here, so if it were the issue, you would have seen it immediately.

Head gasket would be extremely unlikely as a source for an oil leak in this area since the only oil pressure feed for it is at the head bolt on left side between cyls 3 and 4. There are three oil drain passages on the right side but they're only under crankcase pressure (i.e. none, theoretically). Would have to be a radical gasket failure to leak from these.

When you say under the cam belt cover, do you mean you see it generally on the front of the engine or is it specifically coming out the bottom of the timing belt cover near the balancer? Is the balancer wet/slinging oil out?

If you take the timing belt cover off, is the belt wet?

Cam or crank seal failure will wet the backside of the cam or crank sprockets and then fling oil off radially. Big mess but it's easy to pinpoint if this is the issue.