NightmareTA

iTrader: (20)

Well I'm not good with drilling and tapping and unfortunately I started this project before I knew I would have to drill and tap the 3rd hole for the F-body alternator bracket on a truck 5.3 engine. The motor is in the car and I drilled the hole too low and now the bottom "ear" cracked off as I was tapping it. Are 2 bolts (lower bolt and side bolt) enough to hold it in place? It seems pretty stiff and SBC's always only had 2 bolts. I don't understand this shitty design, or why GM felt the need to make car and truck blocks physically different.

If I really need that bolt hole, is there any way I can fix it?

ivan_key

I have heard of many people only using 2 holes, plus people put the bigger truck alt. On f-bodys for more amps and u can only use 2 of the holes and they don't have problems either

NightmareTA

iTrader: (20)

Well I ended up making a little bracket that starts at one of the PS bracket bolts, and comes down to the front of that alt bolt. I threaded the alt itself so the bolt goes through the custom bracket and into the alt. Should hold it fine since it's pretty stiff with the 2 mounting bolts it already had. Guess time will tell. Still think it's dumb that GM didn't thread the truck blocks!!

Frozen WS6

I just discovered this last night as well on my 6.0 truck block. The bigger truck alt will Not work, it needs the upper mounting hole since there is Not the mount on the back of the alt like the stock f body alts have.

00pooterSS

iTrader: (40)

Worst case scenario if your bracket does not work out then you could relocate it to the top

Yeah but the two bolt holes you use, one of them is the lower hole he tried to drill, if you put the truck alternator in and don't have the bottom bolt that he was trying to use, then the alternator is only mounted with one bolt.

It does not need the upper bolt from the rear that the original car alternator uses if that is what you are talking about, me and many other people have been running truck alternators for a long time without that rear bolt. You only need the upper bolt that goes through to the head and the lower bolt that goes through to the block. The other bolt only goes through the alternator bracket.

Hope that all made sense I wrote in a hurry

Frozen WS6

The stock Ls1 block does not have this issue.
It's the upper hole that was never drilled into the iron truck block. Without this hole one has to use the rear bracket to have 2 bolts to hold the alt on. The truck alts do not have that cast into the rear of the case making it unable to bolt up unless one could fab up a new upper bracket or drill the missing hole.
Here are some pics that show the missing hole.

My main bracket.


Front of block.


Undrilled bolt hole.


Holding bracket in place where it goes and the upper bolt should be.

00pooterSS

iTrader: (40)

I see what you are saying, I hadn't looked closely at that before so thanks for the pic's

However I meant to say you don't need the rear bolt hole IF you have the bolt hole drilled/tapped in the block.

Also it looks like you would need to drill 2 holes to use all three mounting points of the bracket right?

And what the heck happened to your bracket? Cut it for non PS belt?

Frozen WS6

I never knew this detail either until I tried to put the 145 amp truck alt I got on earlier this week. So I returned that and got a new stock 105 amp for now. I hope that it can keep up better then the tired old one. If I still have an issue it is from the underdrive crank pulley.

Correct 2 holes would need to be drilled to use all 3 bolts in the main bracket.

I'm not sure why the cut my bracket like that. Unless it was to get it off of an old engine so they could use it on this 6.0.

00pooterSS

iTrader: (40)

I went with the truck alternator because I had I think 8 of those off the shelf alternators fail over and over again, after the truck alternator and 14-15 months I still have no problems. I hope that car alternator works for you.

For what its worth, I wouldn't trust that puny little rear bolt to hold the alternator well, I would drill the hole and use the truck alternator.

If you use a helicoil kit that hole will be easy to drill and tap, the helicoil kit comes with the right size drill bit, tap.. everything.

And I am willing to bet your bracket was cut for a belt that doesn't use power steering, the bolt looks like it is shaved down too. When you run our cars with a belt that by passes the power steering the belt runs right over that lower bolt and can touch.

Pocket

iTrader: (22)

Using the bracket as a guide and use a longer drill bit to drill deeper into the boss. Use a longer bolt to extend past the fracture

Get a quality replacement that wasnt made in china to stop those failures. Rock auto sells ACDelco stuff for $20-40 over autozone prices

00pooterSS

iTrader: (40)

No thanks, I got a higher quality higher output alternator for $40. I tried 4 different brands multiple times, not just autozone crap. Even ones from NAPA were horrible. I even tried new and rebuilt from each supplier several times.

In my DIY truck alternator thread one person even took his car to the Dealership and had them put an alternator on it and it repeatedly failed, so again, not as simple as you think to just go grab a quality alternator. But the factory original alternators were great, that's why I went with the used truck alternator, well that and its higher output and cost $43.30.

Funny part is, I took off the original and replaced it because the power steering pump leaked on it for a while and I was afraid it would fail, so I replaced it, never had a problem until I replaced it. Now I again have no problems with the used truck alternator. Getting a used original is the best way to ensure that you get quality parts, no cheapy garbage parts.

Pocket

iTrader: (22)

I went through 4 alts before demanding my money back and getting an ACdelco unit from RA. Im not repeating stuff Ive read elsewhere. OEM units are great, assuming you can find one that doesnt have an absurd amount of mileage on it. Just who do you think made them?

camross998

iTrader: (2)

dude i did a lq4 swap and im runing only two hole and it fine dude