I could be wrong, but I think the general consensus is that coarse threads are stronger in soft metals like aluminum. That tab on yours doesn't look as thick or beefy as the old original, however. Fine threads are probably less likely to back out on their own in a high vibration application like that, and are sometimes used when the length of engagement is limited -- as it would appear in your picture. That tab doesn't look much, if any, thicker than a steel M10 nut would be...chrischrischris wrote: Tue Feb 24, 2026 1:30 pm The fine (1.25) threads on the m10 bolts are probably specified because they are threading into aluminum. Just a guess, though.
AC compressor mounting bolts
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Tom
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chrischrischris
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I got everything squared away with my rebuilt AC compressor. Ironically, this whole job was only to achieve a working alternator and has nothing to do with restoring my already non-functioning AC. Even when these cars were brand new, the position of the rear mounting bolt is pretty awful and makes the job of installing a new belt or even just tensioning the ac/alt belt cumbersome. I am strongly drawn to the Griffiths compressor kit since it looks like it improves access to the rear compressor mounting bolt and creates a new and better position for the high and low pressure hoses as well as a better location for the low pressure access port.