When I replace the plastic breather gear in favor of a steel, I understand I have to shim it, so do I just measure the plastic gear with plastic spacer, minus the steel gear size and that will be my shim size ?
Put the steel gear in place, put a straight edge accross the cam chest and measure the distance, then subtract the clearance and you have the size spacer you need. They are available in steel from the aftermarket.
Contrary to what you would think the plastic breather tears the bore up more than a steel one. It allows metal particles to embed themselves into the plastic and then they gouge out the bore. Also there are three different plastic breathers, a six slot and a seven slot. If you are going to use a plastic breather in a '84 wet clutch-early 92 use the seven slot (25311-90 prefered or 25312-90) as they have a more advanced timing then the six slot. on later models, late '92-'99 use the 25310-82a. The third one is the one used in the early '84 dry clutch (2513-77b) and should be used as in that model. Hope this helps.