I guessing this is the steel lower bracket, Opel also made an Alum. lower bracket that takes a shorter alt. belt. That would be too much stress on the Alum. :ugh: I have an extra NOS steel bracket if someone needs one for this mod.

 

I guessing this is the steal lower bracket, Opel also made an Alum. lower bracket that takes a shorter alt. belt. That would be too much stress on the Alum. :ugh: I have an extra NOS steal bracket if someone needs one for this mod.

Actually this was using the aluminum mount.
The length of the belt shouldn't make a difference.

There's really not much of a difference in the dimensions, once mounted in the factory bracket, to change the stress load on the lower mount. The length of the belt shouldn't change that in any significant way.

 

Next, I made a list of the hardware I would need and headed off to Ace Hardware.

I purchased it all in stainless steel because it's not that much different in cost to zinc coated to make it worth my while to have rusty bolts in a year.

This is what I got, for about $10

First thing I had to do was to remove the old shims for the rubber grommets because we will be using a 3/8 bolt to fit the GM SI alternator and the shims are smaller than that. They are glued in but it's not too hard to figure a way to remove them using a 1/2 socket, a allen head socket, and a C-clamp.

Then it's really easy to push the new shim in

I thought it would be really important to have the washers in the proper order to make sure everything stays in place.

And this is the final assembly.

The order of assembly is:
Bolt
Flat washer
Bonded washer
Rubber grommet (with new shim inside OE mount)
TWO thick washers
Alternator
Rubber grommet (with new shim inside OE mount)
Bonded washer
Flat washer
Nylock nut.


The parts list is:

• 3/8-16 X 5" bolt
• (2) 3/8 flat washers
• (2) 3/8 .010 thick washers
• (2) bonded washers
• (2) 3/8"ID x 1/2"OD x 1" shim
• 3/8-16 Nylock nut

I used a nylock nut because I don't want to over tighten the mounting.

Everything is stainless.

I have not tested this on the engine yet but everything seems to be lined up.

 

I wouldn't think the length of the belt would change the stress load, those will be felt when the engine is revved. Just thinking that the steel takes a longer belt, it might stand farther off the alt. or block, don't know for sure, might not need to mod. it, but the offer still stands, for the steel one if you want it, that alum. is not that thick to begin with, broke one a few yrs. ago, just my 2ctw :lmao:

 

I wouldn't think the length of the belt would change the stress load, those will be felt when the engine is reved. Just thinking that the steel takes a longer belt, it might stand farther off the alt. or block, don't know for sure, but the offer still stands, for the steel one if you want it, that alum. is not that thick to begin with, broke one a few yrs. ago, just my 2ctw :lmao:

Well, if you want to pass it on to someone who will use it, I would certainly like to use it.
I will PM you.

 

Nice write-up!

Nice write-up! I got about that far on aluminum OE lower bracket mod about 10 years ago, but gave up and went w/the steel GM F. Kinda recall upper bracket mounting boss (when SI alt pivoted in/up against distributor) was farther out & around than I thought I could fab a good upper bracket for. Epic fail for me! :ugh:

 

Been sitting on a new 105 amp GM alternator for years planning to replace the 45amp original on my 75 Manta. Your post may get me off the dime and get er done.

 

If you do, make sure that you replace your ammeter with a voltmeter.

I left my lights on one night and came out to a dead battery. Jump started it and drove off. A couple of minutes later smoke came out from under the dash. The Opel ammeter didn't like being overloaded by a 100 amp alternator.

 

The best SI alternator bracket modification that I have seen, especially to keep the Opel lower bracket with the isolation bushings.

http://www.opelgt.com/forums/1a-2-a...-mounting/44610-gm-si-alternator-using-stock-upper-bracket-belt.html#post482306
Although I do not have a MIG Welder, I like this modification for the SI upper bracket.

Does this qualify for a Sticky so it doesn't get lost?

 

Does this qualify for a Sticky so it doesn't get lost?

Sure....

 

Is it possible to get the alternator Part number for this modification?

Seems to be multiple starter generators with various part numbers that can be used.
Thanks.

 

Here is the one I just used. I am not complete with it yet, but my lower is about done with a slight modification to the process.

3342193 or 10497079, both numbers work. Mine came from Rock Auto for $70 or so.

 

Slight option to this method

I made a small discovery when following this idea for modifying the 94amp 12si that I picked up for my lil GT that lends itself to a bit of an option to this method.

I started with fresh lower bushings, and after a bit more fight to push the inserts out than I cared for, I started scrounging for materials to sleeve the alternator itself to retain the original bolt and still center the alternator on the mount.

What I found in my stash of leftovers was a piece of poly irrigation line that had a wall thickness that was just about but the diameter was way to big. A good pair of scissors had no problem splitting it cleanly and straight, then slowly trimming it down lengthwise to get the diameter correct and have a tight seam when inserted into the alternator mount. The OE bolt is a snug fit and does not wobble at all.

The same gentle grinding and sanding still apply to the lower bracket, mine required a bit on the front for fan clearance and rear lobe for housing clearance. I used the aluminum bracket as it is lighter and this project requires all the weight savings that I can obtain.

Now I just need to setup the shims to locate it properly for pulley alignment and it's good to go.

I can take more pictures later if anyone wants more detailed information. I haven't setup my upper yet, but will putter with that this week.

I really liked First Opel's idea as it was a clean and simple approach to the mounting issue and I would have cloned it if not for the sleeves in the new bushings fighting me.

I hope this opens up another, possibly easier option for those wanting to run a 12SI alternator in place of the OE unit.

As a side note, the AC Delco number for mine, 94 amp, clocked at 3:00 (regulator terminals as viewed from rear) is 3342193 or 10497079, both numbers work. Mine came from Rock Auto for $70 or so.

 

Don't want to turn this into a parts for sale thread but I decided not to use the new si10 105amp on my Thunderbird. It's plugged and wired and standard US shipping is free for $60. See Ad board.
End of my shameless plug.

 

My GT has a replacement alternator, but it is still low amperage so I will be doing this before it hits the road. I noticed that rcvowell has a 12si xxxx for the alternator number and Aardvark has a 10si yyyy for his number. Can anyone tell all of us what those numbers mean?

Thanks, Doug

 

12Si series alternator has several design improvements over the 10Si series that make it the better choice between the two.

Catalog
DELCO REMY models 10SI & 12SI alternators

https://alternatorparts.com/10si-12si-high-output-alternators.html
10Si and 12Si Series High Output Alternators

 

Thanks to you both! :veryhappy

Doug

 

Final mounting of 94 amp 12SI alternator

Here are some pictures of my final mounting. I ended up making two version of the upper adapter to work with the stock upper arm. I didn't like the black one as it came out too short to provide a full swing of adjustment for belt tension. Once the lower was spaced and set to align with the crank and water pump pulley I noticed that a 3/16" or so thick flat bar would work perfectly with some tweaking as the extension.

So I made my second upper adapter and shaped it to insure alternator fan clearance as well as full adjustment swing. Once everything was tightened down it is VERY solid! And should be able to use a stock belt. I will double check that later.

Anyway, here goes with some pictures.

 

Here are some pictures of my final mounting. I ended up making two version of the upper adapter to work with the stock upper arm. I didn't like the black one as it came out too short to provide a full swing of adjustment for belt tension. Once the lower was spaced and set to align with the crank and water pump pulley I noticed that a 3/16" or so thick flat bar would work perfectly with some tweaking as the extension.

So I made my second upper adapter and shaped it to insure alternator fan clearance as well as full adjustment swing. Once everything was tightened down it is VERY solid! And should be able to use a stock belt. I will double check that later.

Anyway, here goes with some pictures.

You better put a large star type lock washer between the brackets because no matter how solid it feels while sitting on your bench it will begin to fold up and loosen the belt when you have vibration from the motor. I have one of those alternators in a box brand new that I never used because I didn't like the way the bracket worked and I went to the trouble to combine an aftermarket bracket with the stock one (welded together) and then had it chromed. It is in the attached picture on the right before I sent it out for chroming. The alternator that I wound up with is 105 amp chrome one and works with the stock bracket.

 

If my chrome gm bracket ever fails I'll be digging out this thread. Nice work..

 

I planned on finding a star washer to put between them for that reason or tweak the bracket a hair to give it a pivot stop to prevent it from folding if it does. The other option was to go back and fold up another bracket like my first one with the mounting centers farther apart. I will run it and see how it behaves. This wont be on the street, but it would still suck to have it loosen up and lose the water pump rotation in the middle of a autocross course!

 

True, I am and was concerned about buckling/slipping when I set it up. A dowel pin can prevent it hinging easy enough. Or do what my first intent was and make a stouter upper like my first one in the picture, just with the correct center to center spacing on the mounting holes. That may still happen, probably will actually now that I found my flat bar I was looking for in the first place! at:

 

Opel bracket didn't work

Today I tried adapting the stock aluminum bracket to work with the GM 105 amp alternator that I had. It is from Autozone - a Duralast 1532-6-7 with the 10 o'clock mounting that I've used previously in my GT and Manta with the F bracket. Upon completing the shim swap and some grinding I discovered that the cooling fan on the alternator will not clear the bracket.

The alternator used by the OP is different and does not have the clearance issues that I had. Looks like it's back to the F bracket for me.:sad:

 

Today I tried adapting the stock aluminum bracket to work with the GM 105 amp alternator that I had. It is from Autozone - a Duralast 1532-6-7 with the 10 o'clock mounting that I've used previously in my GT and Manta with the F bracket. Upon completing the shim swap and some grinding I discovered that the cooling fan on the alternator will not clear the bracket.

The alternator used by the OP is different and does not have the clearance issues that I had. Looks like it's back to the F bracket for me.:sad:

There be two different "stock" brackets..
One is aluminum the other aint.

 

You could find a rebuilder in your area, maybe they can change the fan for a smaller one. The pulley also looks to be a lot bigger than the Opel alternator has, a smaller pulley would improve charging at idle.

 

The pulley is from the original Opel alternator.

 

I've read several of these threads on upgrading the Opel GT alternator. Can someone explain why people are upgrading to higher amperage? Are they adding things to the car that requires more capacity? I have two GTs with original alternators. Both will produce positive current even with everything turned on.

Just asking?

 

With the heater blowing on high, the wipers going and the headlights on, you won't go very long. In this scenario it's a cold wet walk home.

The 35 amps just aren't enough. Not to mention that the Opel alternator is 40 years old and the mechanical voltage regulators are prone to failure.

 

The stock alt can not handle the extra Mods we add to these cars... electric fuel pump draws approx 7 to 10 amp, electric cooling fan up to 30 amps, electric windows, after market radio. Fog / driving lights. all this drains power from the alternator, when you use up all 35 amps the alternator. Is overworking, low power low voltage. Under powered....That why we use a higher amp alternator to handle extra devices

 

I can understand if you are using that many options. I am running a redline weber electric fuel pump on my yellow GT. It is rated at 6 amps at full flow. I don't bypass to the tank, so it is pumping very little and consequently using very little amperage.

I haven't had any issues with alternator output with everything on. I'm running the high output lights from OGTS. Very bright lights.

My first car was an Opel Kadett with the 1.1 engine. I don't remember the alternator output, but it was likely quite low. I mounted airplane landing lights on the front. I don't remember the current draw on these but they had to be substantial. I used to drive it for hours at night in Northern Michigan. I never had issues with charging.

My point is that many of these alternator conversions may be unnecessary. We don't need to modify our cars just because we can. If things aren't working, we should first diagnose the cause. Modifications often result in addition issues that then require more modifications.

 

I've posted these pics before in other threads, here they are again:

 

Here's some more pics:

If you look close at the ends of the fan blades you can see that I ground them down a little. No more than 1/8" I'm sure. I also ground/sanded down the "knobs" on the lower bracket for additional clearance. FYI, I'm using a small crankshaft/large water pump pulley set up, mainly to improve the angle of the fan belt so that it doesn't hit the lower bracket knob. This pulley combo also improves the efficiency of the water pump by making it turn a little slower, thereby letting the water linger a tad longer in the engine to absorb more heat.

 

Here's some more pics:

View attachment 339017 View attachment 339025 View attachment 339033 View attachment 339041 View attachment 339049 View attachment 339057 View attachment 339065 View attachment 339073

If you look close at the ends of the fan blades you can see that I ground them down a little. No more than 1/8" I'm sure. I also ground/sanded down the "knobs" on the lower bracket for additional clearance. FYI, I'm using a small crankshaft/large water pump pulley set up, mainly to improve the angle of the fan belt so that it doesn't hit the lower bracket knob. This pulley combo also improves the efficiency of the water pump by making it turn a little slower, thereby letting the water linger a tad longer in the engine to absorb more heat.

Thanks for the pics Scifi Guy, I remember some of them from another thread. It looks like you have the same alternator I show in my previous post. Now I see that the clocking of the upper mounting ear is more towards 9 o-clock than the Opel, so you had to make that little bracket. I like that reduction sleeve for the lower bolt versus reaming out the Opel bushings. I guess there isn't a way to use the oe upper bracket unless someone can rebuild a Bosch to 105 amps. I know most won't need that high an output but I plan on putting fuel injection, electric fan and electric power steering so it is going to be necessary.

 

I had(and still have) the toothed pulleys. I took them off because they were noisy and there was a lot of slop between the teeth. The nice thing about them is that you don't have to have any tension on the belt at all. Some Opelers have discovered that if they make their V-belts too tight to prevent slippage and squealing, this skews or pulls on the crankshaft pulley which causes oil to creep by the front seal. This causes a spray of oil on your hood and engine.

The pics DO show the mod that allows you to use the oem upper bracket. You have to make an offset extension piece that lifts the bracket so that it doesn't touch the fan blades. You have to use 2 bolts in the bracket slot so that it doesn't pivot.

I got the brass tube, to shim the bolt diameter difference on the SI's lower bracket bolt hole, from my local ACE hardware store in their craft metal/small tubing display rack. I still have the leftover tubing, I could send a few 3" long pieces to folks who need it.

 

I meant multi-rib not toothed pulleys. Like these:

This picture is from Kieth's thread

http://www.opelgt.com/forums/opel-g...restoration-project/28118-opel-gt-restoration-taken-extreme-logbook-file-5.html

 

A couple things....

I opt to just get rid of the rubber bushings, and turn aluminum press fit ones into the original brackets
I also do this for the top OEM arm. Every other factory alternator setup I have seen is solid, so I'm not sure why Opel used rubber isolators, but as soon as you tighten those down, they flex back. And you do not get a good ground through them, so why not eliminate them?
Also I find that the hole in the timing cover is too big of a diameter, so I found a piece of drill rod through McMaster Carr that is a good press fit in that hole, and I drill a 5/16 hole in it to take out the slop of the hole. I was finding that the bolt would move side to side a bit and mess up the adjustment. I provide this with the A/C kits including a factory bracket modified for this.

 

I suppose a lot of the breakage problems would go away if the upper rubber was replaced along with using the F-bracket, even incorporating a rear brace like suggested earlier. I haven't got to the end of the build thread yet but do you have any plans to make those multi-rib pulleys Kieth? It doesn't have to be serpentine with idlers and tensioner, just use the factory adjustment method.

 

Also Gordo, isn't your alternator a CS130, not a SI? The ribbed spacer and offset of the mounts I think it is, but I'm not used to seeing a positive terminal on the back like yours has. I would just have added some welds to the chrome F Bracket, and then grind the lower part of the upper bracket for fan clearance, no? Here is a pic of the upper bushings I make

 

Another reason for using the original bottom bracket over the F bracket is the alternator sits lower with the factory mount. Lower CG=Better Handling.:haha: