AKFL

Hello! This is my first post in this forum, so here goes. I have a 1986 F150 with the 351. I replaced my alternator belts, but discovered one of my bolts for the alternator mounting bracket has fallen out. Consequently, I can't apply tension to my belts. I've searched high and low through different websites, available online manuals, diagrams, and videos to try and help figure out what size bolt I need or if I need any other hardware to keep the bolt in place. I've found nothing helpful. Specifically, it's the bolt on the top bracket. Can anyone advise what size this is? Thank you in advance. I know this is probably a stupid simple question... If this is the wrong place to post, just let me know and I'll fix it.

Steve83

There are many possible configurations - you need to post a LOT of pics, and put all the truck's details into your signature as this caption explains:

(phone app link)

AKFL

Sorry about the delay, got busy yesterday. Here are the photos. Are the bolts the same size, or are there different size bolts depending on where they're mounted?

Steve83

Looks like you got all the bolt pieces out - just take them to a local hardware store, and match them up. Or swing through a local JY and grab a few. That bolt should be the same regardless where it's installed on the pump. Note the rear hole in your last pic, which is threaded the same. Most later trucks up to ~'96 use that hole, so it may be easier to find a bolt from one a newer truck than yours.

AKFL

So is it just the bolt I need, or is there more internal hardware?

raski

That missing bolt would tension the A/C belt, is the alternator belt able to be tensioned with what you have? It would be independent of the compressor and you did not show any detailed pics of the alternator.
Often bolt sizes are identical. I would remove one of the easier accessible bolts on the a/c compressor (like the one under the pulley) and see if it threads in the empty hole. If it does, determine the length you need using a nail, take that bolt with you and get a grade 5 or 8 bolt, a flat and lock washer and you should be good to go.

Steve83

The bolt screws directly into the pump housing, where you can see the threads in your photo.

AKFL

Here are some photos of the alternator. What do y'all think?

raski

You are good to go with the alternator.You can even see where the alternator was on the bracket when it was tensioned. Loosen top and bottom bolts, pull up the alternator and tighten them. You shouldn't need to loosen bolts holding the bracket to the engine.Do this before tensioning the a/c belt.If you haven't gotten the needed bolt for the a/c compressor, once you tension the alternator belt, you can drive it with the a/c belt off till you get the bolt.

AKFL

The truck had to sit for a bit because I didn't have the time to work on it; I do now. Are the top and bottom bolts both on the front of the bracket? The only bolt I'm finding is the top one and that's the bolt that allows the bracket holding the alternator and compressor to pivot. I'm not readily seeing a bolt for the bottom of the alternator bracket.