Dear Andrew in AL,

Hope you're well. The crank pulley bolt is not likely to have stretched. As trichard suggested, the faulty installation likely ruined the crankshaft sprocket. The sprocket is Part #9135271. and costs about $75 at a Volvo dealer. The timing belt rides on the crankshaft sprocket.

the crankshaft pulley (a.k.a. Harmonic balancer) is locked into the crankshaft sprocket, by a square projection on the sprocket's front face, that fits into a square recess (notch) on the reverse-side of the crankshaft pulley. Getting the pulley's notch aligned with the sprocket's projection takes some care: the projection is only about 1/16" forward of the slightly conical steel washer, that keeps the timing belt aligned on the sprocket

I'd have a replacement sprocket handy, as if it indeed has been ruined, the re-assembly cannot be completed.

I'd not drive the car until the harmonic ballancer has been re-installed, so that it spins true.

Hope this helps.

Yours faithfully,

Spook