There is no push rods on the 2.5 Subaru engine. The heads have a single over head cam and that's the main reason I have no idea if valve adjustment can be set accurately off the block. I just don't see why not and thought possibly some one has crossed this road before.Is this a pushrod engine like a VW? If so, then there will be no lash until you have the cam, lifter, pushrod, rocker, valve relationship established.
Thank you Hot Wings. I thought as long as the cam lobe was not forcing the spring down and opening valve valve lash could be set more precise and much easier on the bench. Thanks again to all. DonKind of depends on which Subaru version you are working on. Normal in the car valve adjustment is done cold and should make little difference if the head is attached to the bloc or is on the bench. If you have a bucket lifter version the only practical way is to do the adjustment on the bench. I'm not well enough versed on all of the Subaru variations, but if there is a bucket valve version with hydraulic lifters than there will be an additional bit of procedure to follow.
IMHO the non-hydraulic Subaru bucket valves are not such a great idea. The last time I worked on an OHC with non field adjustable lash was an old Aston Martin. My brother is on his third set of Subaru heads due to burned valves. In fairness it's not all the designs fault. He needs to find a better mechanic.
Edit: just saw the pics. Do it on the bench.