Why does it need to be done warm when both the service manual and Haynes specify the same clearance for both warm and cold?

The manuals are weird. For the B18, they specify .004" greater clearance when set cold than when set hot. For the B20, with a nearly identical valve train, they say set it to the same specs hot or cold. ???

In actual practice, I find that the valve train expands with heat, and tightens up about .002" in doing so. It's not completely uniform, so the results are more consistent when set to the tight end of the spec fully hot.

This is actually common practice for most OHV motors of any marque, European or American. It's strange the Volvo manuals are so vague about it.

Any other tips beside this method?

Every time I mention anything specific about valve adjustment on this forum, someone is sure to jump in and say it's all wrong... so I'll just say that this method truly is more accurate than either the Volvo manual method (really quick and dirty) or the Haynes, and that to me it's worth the slight extra labor involved. But I'm picky.

There seems to be a lot of gunk in there. I plan to wipe it out using a cloth and carb cleaner. OK?

Sure, but don't let anything run down the pushrod holes in the head.

The valve cover is pretty much cemented in place with a blue colored gasket sealant. I'm going to scrape this off and replace the gasket. I have a both a cork and a rubber one from IPD. Is one better than another?

I prefer the cork gasket with the stock valve cover. Take the time to tap out any dimpling around the hold-down bolt holes and make sure the gasket surface on the cover is really flat.

I also plan to use the IPD valve cover hold down set for insurance against leaks.

The one with the little spreaders under the bolt heads? That works very well. Use lock washers between the bolts and the spreaders, and don't tighten it any more than is necessary to flatten the washers.

--Phil