GM SI alternator mount using original lower bracket

11861 Views 58 Replies 22 Participants Last post by Red0ktober, Oct 21, 2017

First opel 1981

Discussion Starter · Mar 31, 2014 (Edited)

12

I was playing around with the GM SI alternator and figured an easy, painless, way to use the original bracket.

I am sure a few would like to know how I did it so here's the write up.

First thing I did was look to see how different the lower mounts were. There's enough of a difference so that you can't just put the alternator into the factory bracket but as you see from the following pictures, not so much that it's not doable.

I first measured the position of the pulley vs the lower mount on the alternator.
I discovered that the back part lines up within a few thousands of an inch but the front was shorter on the GM alternator by approximately 0.2 inches

I figured if I have the right shim in place then I could just space the front and everything would be cool, right?

So now I fitted the bracket to the alternator to see if the mount clears the housing.
With the factory bolt it would but there was never going to be a situation where it would fit centered in the hole. This could cause problems down the line.

So, still using the factory bolt, I utilized the fact that the mount had been sprayed black and moved it a few times to see how much, and where, it was binding.

I then observed that there would be plenty of meat left on the bone if I ground it down to clear with a centered bolt. I ended up grinding off about .050" of the mount to clear. The alternator housing has a slight angle to it so one side needs to be ground more than the other.

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41 - 59 of 59 Posts

Mark B

· #41 · Oct 16, 2017

Opelmel said:
The pulley is from the original Opel alternator.

It does look like the pulley on my alternator, is your alternator smaller physically than the Bosch? That would explain the confusion. In any case if it is only the fan that is hitting I would try to locate a smaller one or cut yours down. I like that the tab is clocked as the original, were you able to use the original upper adjuster?

Opelmel

· #42 · Oct 16, 2017

The Scifi Guy said:
There's something odd about the fan in your pic. It looks as though, in places, it appears to be larger than the housing of the alt. I think I ground the tips of my fan off by eye with an angle grinder on my bench, then to make sure the fan was balanced I held a file or maybe the grinder near the fan blades as it spun with the engine running and got them all evenly balanced.

That's one of them thar optical delusions. The fan blades are all the same length and all are within the perimeter of the alternator housing.

Opelmel

· #43 · Oct 16, 2017

Mark B said:
It does look like the pulley on my alternator, is your alternator smaller physically than the Bosch? That would explain the confusion. In any case if it is only the fan that is hitting I would try to locate a smaller one or cut yours down. I like that the tab is clocked as the original, were you able to use the original upper adjuster?

I can't compare sizing of the alternators, since I gave my Opel ones to other Opelers. The pulley diameter is approx. 2 7/8".

The Scifi Guy

· #44 · Oct 16, 2017

8

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

Line Text Diagram Parallel

Parallel Circle

Technology Electronics Auto part Electronic device

Auto part Automotive lighting Suspension Heat Suspension part

Auto part Automotive exterior Exhaust system Bumper Muffler

Auto part Motor vehicle Engine Vehicle Car

Auto part Vehicle Engine Fuel line Automotive wheel system

Auto part Engine Fuel line Automotive engine part Vehicle

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The Scifi Guy

· #45 · Oct 16, 2017 (Edited)

8

Here's some more pics:

Auto part Technology

Auto part Bicycle pedal

Yellow Auto part Tool

Auto part Carbon Steel Metal Automotive exhaust

Auto part Engine Automotive engine part Machine Metal

Auto part Engine Automotive engine part Tire Automotive wheel system

Auto part Engine Automotive engine part Carburetor Fuel line

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.

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Mark B

· #46 · Oct 16, 2017

2

Opelmel said:
I can't compare sizing of the alternators, since I gave my Opel ones to other Opelers. The pulley diameter is approx. 2 7/8".

Yeah, my pulley is that size. That's anuther one of them thar optical delusions. :yup: I am looking at a cs130 alternator from 88-90 Camaro that is almost identical. The CS series are supposed to be a newer, more efficient version. If it's smaller and lighter than the original so much the better. Is there any problem wiring one of these up? Would be nice to convert to multirib belt to prevent slippage. Does anyone have pulleys for that?

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Mark B

· #47 · Oct 16, 2017

The Scifi Guy said:
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.

The Scifi Guy

· #48 · Oct 16, 2017

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.

opelspyder

· #49 · Oct 16, 2017

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.

opelspyder

· #50 · Oct 16, 2017

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

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Mark B

· #51 · Oct 16, 2017

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:

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Mark B

· #52 · Oct 16, 2017

The Scifi Guy said:
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-taken-extreme-logbook-file-5.html

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Mark B

· #53 · Oct 16, 2017

opelspyder said:
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.

opelspyder

· #54 · Oct 17, 2017

Mark B said:
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.

The cost was too much for the serpentine pulleys, then some drawbacks came with the setup as well. Not just that, but the brackets were pricey too. I liked the idea, but when the engine parts cost more than my complete air conditioning system running a V-belt setup...I had to come up with a new plan.

Red0ktober

· #55 · Oct 21, 2017

SI is old tech. I put a 105 amp CS130 on my Kadett with zero problems. Using the original lower bracket with a bit of old trans cooler tube as a sleeve over the bolt to bring up the OD, and a universal upper bracket bent and drilled to fit. There is an application of the CS130 with a v-belt which is what I used.

wrench459 (R.I.P.)

· #56 · Oct 21, 2017

My question is

Why do you need a high output alternator?

Red0ktober

· #57 · Oct 21, 2017

Me? I was building my car for the LeMons Rally. I needed power for my Megasquirt, fuel pump, e-fan, stereo, CB, crock pot, laptop and phone charging, etc.

Also I wanted a modern, internally regulated, readily available, and reasonably priced component.

wrench459 (R.I.P.)

· #58 · Oct 21, 2017

Red0ktober said:
Me? I was building my car for the LeMons Rally. I needed power for my Megasquirt, fuel pump, e-fan, stereo, CB, crock pot, laptop and phone charging, etc.

Yuck,yuck
I hate it when my butt warmer's won't get up to temp. when racing.

Red0ktober

· #59 · Oct 21, 2017

wrench459 said:
Yuck,yuck
I hate it when my butt warmer's won't get up to temp. when racing.

That might be accurate if I ever do one of their winter rallies.

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