Hi guys, first of all YES I have used the search function for this and just could not find my answer. I have acquired all of the parts for my 3rd gen alternator swap into my '82, however I need some help with the alternator bolt size for the FD alternator. Some threads said it was a 9mm? Can I reuse my stock bracket or do I need a different one?

Thanks!

 

I can't answer your specific question but I can relay my recent experience. I installed an FD alternator that lacked a bolt on an FD engine in an FB. It was the 12mm head bolt that tensions the belt. Not the 14mm long bolt that you're not having trouble with.

Since the FD alt has a through-hole instead of threaded, I had to come up with a long 8mm x 1.25 bolt and a nut on the back. However because the stock tensioner was missing, I couldnt take advantage of it, so I had to make sure the new bolt had a good grip on the bracket. And now I can't remember what I used.

PercentSevenC might see this and might remember what was used. It was his car and I needed to solve this problem quickly and move onto the next one.

I might have used a big washer or something? To spread the force out over a larger area. A picture would speak a few more words better than I could but I didn't take any.

Anyway the bolt is a 12mm head, large round section, 8mm x 1.25 thread pitch. Length is long enough to get all the way through and have a nut on the back side. If you're looking in a hardward store, the bolt will have a 13mm head and will require a washer. Get a hardened washer or a thick one.

 

Thank you for the excellent answer! My initial thoughts were to use a large washer and torque it down to securely fasten it to the tensioner. However, I just am trying to minimize any of the risk of the large bolt failing, causing the alternator to let go. Do you happen to know the proper way it is secured to on a stock FD? Also, is it a 12 or 13mm head? you mentioned both......

Thanks so much!