This is for a non-Honda, but I trust the brains at H-T more than my usual Volvo forum for this question.

I just put a junkyard motor into a Volvo that had blown a head gasket. The coolant reeked of oil. I bought a nice, new radiator to use, BUT, I want to do a cooling system flush to clean out any residual oil that might be in the heater core + I want to flush out the water jackets of the donor motor.

What I DO NOT want to do is flush all this crap into my new radiator. I've still got the old one. In your opinion, is it wise to reinstall the old radiator, fill with the coolant flush and water, run it, drain it,THEN put in the new radiator? It's going to add a few hours to the project but I haven't used one of these flushes before and I don't know how much sludge and solids it may dislodge. OR, is this being overly cautious?