is a retorque needed if installing head studs but not pulling the head .just one at a time any info would be great.

 

Check your lash before you torque it, and check after. If the lash tightens up, you just squished the head gasket more. I'd think it wouldn't change much, but the time it takes to do a retorque, it wouldn't be a bad idea. Probably half the time to do it on a 24v as a 12v, so you're lucky.