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Alternator Mounting

LannyL81

Well-known member
Joined
Jul 20, 2002
Messages
653
Location
Oro Valley, AZ USA
Corvette
81 White/Cinnabar, 96 CE LT4 sil/blk
My '81 has the 1st design or cast iron lower bracket and then the long tension bracket. According to the Assembly Manual, this is the brackets for the non-70 amp version. But I am thinking that a previous owner put the larger alternator on as I cannot remove the alternator belt unless I remove the alternator itself. The alternator hits the valve cover before there is enough slack in the belt to go over the alternator pulley.

Is the non-70 amp alternator really small or something? The car has A/C so I though it should have come with the larger alternator.

Comments.....
LannyL81
 
Joined
Apr 29, 2001
Messages
2,141
Location
Rio Rancho, NM
Corvette
1981 HD Suspension; ZN1 Option
My '81 has the 1st design or cast iron lower bracket and then the long tension bracket. According to the Assembly Manual, this is the brackets for the non-70 amp version. But I am thinking that a previous owner put the larger alternator on as I cannot remove the alternator belt unless I remove the alternator itself. The alternator hits the valve cover before there is enough slack in the belt to go over the alternator pulley.

Is the non-70 amp alternator really small or something? The car has A/C so I though it should have come with the larger alternator.

Comments.....
LannyL81

Hey Lanny, good to hear from you.

My car has the aluminum bracket, but I also have always had the problem you describe with either alternator. I am not sure if the local auto parts stores have cataloged the wrong alternator belt part number or what. But I just went out to my garage, and I looked at the set-up on it right now, and without the proper tension on the belt I have about 1-3/4" of the adjustable bracket slot space unused. The alternator body is about an inch from the valve cover.

I just received the proper stud that goes inboard of the brackets 2 bolts from Dr. Rebuild, and it corrected the alignment of the adjusting bracket with the alternator body. I also have other views on the engine, so that it can perhaps help you compare with your set-up.
http://l81power.spaces.live.com/?lc=1033 Select "L81 Engine Configuration" on the photos pane (The better shot showing the alternator is somewhere between image #26 and #29).

GerryLP:cool

p.s. I think you're right. I believe that the L81's had standard A/C, and the 62 amp alternator was not enough to maintain the battery in good order and charged.
 

LannyL81

Well-known member
Joined
Jul 20, 2002
Messages
653
Location
Oro Valley, AZ USA
Corvette
81 White/Cinnabar, 96 CE LT4 sil/blk
Hey Lanny, good to hear from you.

My car has the aluminum bracket, but I also have always had the problem you describe with either alternator. I am not sure if the local auto parts stores have cataloged the wrong alternator belt part number or what. But I just went out to my garage, and I looked at the set-up on it right now, and without the proper tension on the belt I have about 1-3/4" of the adjustable bracket slot space unused. The alternator body is about an inch from the valve cover.

I just received the proper stud that goes inboard of the brackets 2 bolts from Dr. Rebuild, and it corrected the alignment of the adjusting bracket with the alternator body. I also have other views on the engine, so that it can perhaps help you compare with your set-up.
http://l81power.spaces.live.com/?lc=1033 Select "L81 Engine Configuration" on the photos pane (The better shot showing the alternator is somewhere between image #26 and #29).

GerryLP:cool

p.s. I think you're right. I believe that the L81's had standard A/C, and the 62 amp alternator was not enough to maintain the battery in good order and charged.

GerryLP,
Thanks for the response and the link to the excellent photos you have. I did not think about Dr Rebuild for that stud...I went to Corvette Central and have one on order. I had them measure its length for me....sure hope it fits. They list the same stud for the upper left water pump as the alternator tension bracket...whereas the GM Assembly Manual lists two different part numbers. Also, the stud for the alternator is longer than the one for the water pump position. Trust me...I tried to use that stud for the alternator...was not long enough to even go through the aluminum alternator bracket.

So are you tellimg me that you have to remove your alternator pivot bolt in order to get the belt to slip over the alternator pulley? Do you know if you have the larger alternator? I would like to see what a 62/63 amp alternator looks like in comparison to the the one that I have. And you may be right that about the belt part number being wrong. I got the part number out of the Owner's Manual....but it could still be wrong. I believe it listed only one alternator belt...so must be the same for either size alternator.

Oh well.....things to live with. Not like I take the alternator belt off / on that often....but I did when I was trying to find out what was going on after my engine rebuild. I presently have the AIR pump off and will have to put in back on over Thanksgiving in preparation for my emissions check in Dec.

Thanks again....
LannyL81
 
Joined
Apr 29, 2001
Messages
2,141
Location
Rio Rancho, NM
Corvette
1981 HD Suspension; ZN1 Option
... I would like to see what a 62/63 amp alternator looks like in comparison to the the one that I have.
Thanks again....
LannyL81

Lanny,

My car had the 70 amp alternator, and when it broke, I took a chance with the lower-amp rating alternator, but it's just not enough (the additional 7 or 8 amps make a huge difference with the battery, I guess). So, I went out for another 70 Amp alternator.

I'll try to get an image of both for comparison purposes. I'll also measure the body to see if it is different at all.

GerryLP:cool
 
Joined
Apr 29, 2001
Messages
2,141
Location
Rio Rancho, NM
Corvette
1981 HD Suspension; ZN1 Option
Lanny,

I just measured the 70 Amp alternator, and it is 5-3/4" diameter when measuring it perpendicular to the mounting bosses. The mounting bosses are 8" apart at their most extreme points.

In comparison, the 62 amp is smaller by 1/2" in both dimensions I mentioned above. So overall, the 70 amp alternator is about 1/2" larger.

Still, it doesn't explain why the difficulty on changing belts. Perhaps is as we mentioned (the difference in belt manufacturers and part suppliers) and also perhaps the mounting bracket, since in my case, the one thing staying the same is the bracket.

I definitely recommend switching to the 70 amp alternator for the battery's sake.

GerryLP:cool
 

LannyL81

Well-known member
Joined
Jul 20, 2002
Messages
653
Location
Oro Valley, AZ USA
Corvette
81 White/Cinnabar, 96 CE LT4 sil/blk
Jerry,
Do not know what happened to the text I put here on the 21st....oh well...I'll put it again.

I installed the aluminum lower alternator mount and the shorter tension brackets...but still have the same problem, plus a new one. With this new mount the two pin connector is in-line with the pivot bolt. So now I have to remove the connector to get to the pivot bolt. I am wondering if I have a wierd alternator or something?? Where is the two pin connector on your alternator in relation to the pivot bolt?

Oh and I have the larger alternator...just not sure if it is the correct one or not....but it works.

Lanny
 

LVMYVT76

Well-known member
Joined
Apr 21, 2006
Messages
664
Location
springfield, mo
Corvette
1976 medium blue
I know that when I put the alum valve covers on , I had to buy a longer belt because the valve covers were taller and made the alt. be out more. Are your valve cover stock??
 

LannyL81

Well-known member
Joined
Jul 20, 2002
Messages
653
Location
Oro Valley, AZ USA
Corvette
81 White/Cinnabar, 96 CE LT4 sil/blk
I know that when I put the alum valve covers on , I had to buy a longer belt because the valve covers were taller and made the alt. be out more. Are your valve cover stock??

I have the stock L81 valve covers. But I might have the wrong alternator. But not worth getting another one as this one works just fine. Just a pain at times.

Lanny
 
Joined
Apr 29, 2001
Messages
2,141
Location
Rio Rancho, NM
Corvette
1981 HD Suspension; ZN1 Option
Jerry,
....Where is the two pin connector on your alternator in relation to the pivot bolt?
Lanny

Lanny,

I just looked at my engine, and the dual-blade connector should be 90 deg offset or perpendicular to the pivot mounting bolt. I believe what you have to do is remove the 4 thru-bolts that hold the front portion to the alternator body and rotate the stator assembly so that the dual-blade connector is pointing straight-out to the left side (driver side) fender. So when looking at the alternator from the rear, and using a clock-like orientation, then the dual-blade connector is at 9 O'clock and the mounting bolt (pivot bolt) is at 6 O'clock.

Now, I recognize that the shop manual shows the dual-blade connector aligned with the top (tensioning) bolt hole, but I have had my vette since it had 16K miles, and it has always had the dual-blade connector pointing at the fender (not aligned with adjusting bolt hole location). Not real evidence, I know :eyerole , but I believe it is right.

GerryLP:cool

View attachment 11017
 

mkapp7879

Well-known member
Joined
Feb 17, 2004
Messages
398
Location
Beecher, Ill.
Corvette
78 Pace,black 79 and white 79, all L82s
Thought I'd chime in on this as I had some similar problems today. I'm changing belts on two of my Vettes, one 78 and one 79 because the alternators were at the very end of their adjustments. 78 calls for a .370X53" belt and the 79 calls for a .370X52" belt. Well, DocRebuild sent me out .440X52 and 53s. Couldn't get the called for 53" on the 78 but it ended up fitting perfectly on the 79 which called for the 52. So...apparently, going from .370 to .440 width requires adding another inch to the length. I'll be exchanging the 79s 52" for a 54" to use on the 78. Mike
 

LannyL81

Well-known member
Joined
Jul 20, 2002
Messages
653
Location
Oro Valley, AZ USA
Corvette
81 White/Cinnabar, 96 CE LT4 sil/blk
Lanny,

I just looked at my engine, and the dual-blade connector should be 90 deg offset or perpendicular to the pivot mounting bolt. I believe what you have to do is remove the 4 thru-bolts that hold the front portion to the alternator body and rotate the stator assembly so that the dual-blade connector is pointing straight-out to the left side (driver side) fender. So when looking at the alternator from the rear, and using a clock-like orientation, then the dual-blade connector is at 9 O'clock and the mounting bolt (pivot bolt) is at 6 O'clock.

Now, I recognize that the shop manual shows the dual-blade connector aligned with the top (tensioning) bolt hole, but I have had my vette since it had 16K miles, and it has always had the dual-blade connector pointing at the fender (not aligned with adjusting bolt hole location). Not real evidence, I know :eyerole , but I believe it is right.

GerryLP:cool

View attachment 11017

GerryLP,
Yes I agree...I have been looking at alot of 80 and 81 engine pictures to see how that alternator is positioned and almost eveyone I saw had the two pin connector pointing towards the driver's fender. Soooo....going to take mine off this weekend and rotate the housing and make it right!!! I have no idea where this alternator came from...was on the car when I got it. But right now the connector gets melted from the heat off the exhaust manifold...which is why I had to change it as part of the engine rebuild. Never thought about taking the alternator apart and rotating the housing...duh....
Thanks again for the assistance.

LannyL81
 

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