Correct A/C compressor pully diameter for '85?

Robby85

Parts stores offer the compressor with three different pully diameters, 4.9. 5.0 and 5.4. My existing one looks like it is the 4.9. I recently replaced the original 3 speed transmission with a 4 speed. Does engine RPM have anything to do with the puuly size. And I will be converting from R-12 to 134 if that might make any difference.

Thanks
Robby

rhimmel · Posted: Thu Jul 03, 2008 5:12 pm Post subject:

Generally speaking, the diameter of the pulley would change the compressor speed at a given engine RPM due to the ralationship of the Comp. pulley vs the Crankshaft pulley. I would suggest that you match what is currently on the vehicle as it also changes the belt length. Through my experience with GM's the diameter or RPM variance of the compressor doesn't realy seem to effect the pressures by any real notable difference. IF you keep te size that you currently hav, then the belt size that you have will work without any issues.

Rob
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Rhimmel
'81 El Camino

hawgs74 · Posted: Mon Jul 07, 2008 5:04 pm Post subject:

How do you tell the pulley diameter without taking it off?
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85 Conquista SS

rhimmel · Posted: Mon Jul 07, 2008 10:05 pm Post subject:

If you can get me the Harrison number off of yours, I can then cross reference that and then tell you which one is a direct replacement. I think that would be the easiest. I can most likely give you a majority of the part numbers that it crosses to regardless of the vendor. That number usually starts with a "113" if I remember correctly and is about 6-8 digits long.

-Rob
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Rhimmel
'81 El Camino