I don't think you can get the bolt out even with the valve cover off. I wound up taking the whole dang compressor bracket loose to get it out on mine, just to change the water pump.
Whatever compressor you get, don't try to save a few bucks on a reman..get NEW. This is one job you do NOT wanna hafta do twice. Reman compressors are a crap shoot. Get a new GM/Delco from a major parts house....you'll be glad you did. You can run 134 in the system as is, as long as your hoses are in good shape. If they are questionable, replace them. Also replace the dryer/accumulator....they will not warranty the compressor if you don't. Take the orifice tube out of the high pressure line and clean, or replace it. The orifiace tube on the '85 is in the tube just in front of the evaporator box/case, in the tube going down to the bottom of the case.
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Joel Adams
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"