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R134 retrofit for 1975 280z


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I thought I would share how I went about converting my old R12 system in my 1975 280Z to R134a. My system charged up OK after sitting dormant since 1995. It still had a charge in it but not enough to cool the air. Once charged it put out about 50 degree air on a 102 degree day (good) but the old Hatachi compressor made some really nasty noises (bad). The compressor was louder than the motor while driving down the road. I worried that the dying compressor would contaminate the system and if it plugged up the expansion valve I would be up the proverbial creek without an adequate means of propulsion.

I am trying to keep the engine compartment/car looking relative stock. I upgraded to a Sanden 508 compressor and then adapted it to the stock compressor bracket that mounts on the side of the L28 block. I chose to stay with the original bracket because it incorporates the belt tensioning pulley and it is stock. I know that you can purchase aftermarket brackets that will bolt up to the block (and I have to believe that they have to weigh a lot less) but to tension the v-belt you must rotate the compressor and again it does not look stock. I could have made my own bracket but it would have been similar to the stock bracket.

Unfortunately the mounting ears/pads for the Hatachi compressor do not match up with the Sanden but by making some spacers and a bottom bracket the Sanden bolt up to the Datsun's bracket with no modifications to the bracket. To do this adaption you must have access to a welder, a metal lathe, some 7/8" round stock, a small piece of 3/8" flat stock and a good caliper to make some accurate spacers. First I made a small spacer out of 7/8" dia. material with a 10mm hole (you can use a 'X' letter drill) that would align the second groove of the Sanden's pulleys with the stock tensioner pulley on the Datsun's bracket. Once this is done then you can make two additional spacers. Each of these spacers must be made so that they just barely fit in position. If you have too much space you risk breaking or cracking one of the mounting ears off your new compressor which would probably ruin your day. In the first picture you can see the arrangement of bolts and spacers. You will need to purchase metric allen head bolts because of the space needed to tighten them up will not accommodate a hex head bolt. From the left I have a 42mm long bolt, a .184 thick spacer, the next spacer is drilled and tapped for a 10mm x 1.5 on both ends to allow the tightening of the two opposing bolts. The next spacer is drilled20210715_142136.jpg all the way thru and a 80mm long bolts passes thru it and threads into the previous spacer. 20210715_141947.jpgHopefully the second picture will show how all of this goes together. 

In order to attach the bottom compressor mounts you will need a 1 1/2" x 5" x 3/8" piece of metal that is notched to allow it to fit in the area that the old Hatachi compressor bolted to. Cut your metal, notch it and transfer punch two marks that will be drilled and tapped for 10mm x 1.5 threads. You will also need to make a 7/8" diameter spacer that fits between the two bottom ears of the Sanden compressor (get a good fit with very little clearance). This spacer needs to have both ends drilled and tapped for 10mm x 1.5 threads to accommodate two 10mm alllen bolts that are 30mm in length. You will need to make the flat plate out of 3/8 and the bottom spacer out of 7/8 diameter stock so that when the two come together there will be enough area at their intersection to complete a good weld. 

Bolt the compressor up to the bracket's top mounts with your three spaces and bolts, attach the flat plate to the bottom of the bracket with 10mm x 28mm long bolts, mount the bottom spacer onto the Sanden's bottom ears and rotate the compressor so that the bottom spacer and flat plate meet. Make sure your pulleys are aligned, my narrow spacer (.184)may be a little different than your application, tighten up the top bolts and spacers and tack weld the bottom spacer to the flat plate. I then pulled off the bottom bracket and tacked welded it on the back side and reinstalled it to make sure it did not pull out of alignment. It was good so I finished welded it, put it back on and checked it again and then pulled it off, bead blasted it and put a coat of paint on it. Pictures 3, 4 and 5 should help explain. Done. Tomorrow, I will start the install of a new condenser with o rings onto my radiator and how I will go about making connections onto the existing flared hard lines.




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Well done. I like they way you managed to keep the original bracket and adjusting pulley.

I have seen other aftermarket options where the compressor moves to tension the belt. Not much space down there for that kind of adjustment.

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I forgot to mention, the correct length belt for this new modification is a Gates XL 9350 (15/32" x 35 3/8" or 12mm x 899mm). I barely fits over the pulleys with the tensioner pulley completely slack and when the tensioner  pulley tightens the belt properly it still has about 3/4" of travel up.

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Thanks for sharing. I can only fit the belt on my hitachi compressor by removing the adjusting pulley, fit the belt and then insert the adjusting pulley and retighten. The tensionef is then about half way when the belt is tensioned. My belt may be one size to small.

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