Correct 70 350 hp 1100990 alternator?

[Mike E.]

This is purportedly an original alternator. Supposedly recently taken off a running 70. My suspicions are raised when I see that the rear case is clocked 90 degrees off from where it should be in relationship to the front. The stamping is good and looks old. Does the rear of the case appear correct, and should it have the raised rectangle by the Delco-Remy or not? Which pulley fan is correct--the one that has 3 ribs on the wide vanes, or the one that has two and a flat space where the third would have been? Thanks for your input.

[David L.]

Re: Correct 70 350 hp 1100990 alternator?

Mike,

Here is a link to the "shark tooth" alternator fan like the one on your alternator.
The pulley looks like in might be GM # 1970831. Does it measure 3.20" O.D. and about 1.40" I.D.?
Are you sure the alt. number is "1100990" or could it be "1100900"?

Dave

https://www.forums.ncrs.org/showthread.php?88453-68-69-70-quot-shark-tooth-quot-alternator-fan-1969448&p=569632#post569632

[Mike E.]

Re: Correct 70 350 hp 1100990 alternator?

Dave,
thanks. It's a 900, not a 990. My bad-typo.

[Joe L.]

Re: Correct 70 350 hp 1100990 alternator?

This is purportedly an original alternator. Supposedly recently taken off a running 70. My suspicions are raised when I see that the rear case is clocked 90 degrees off from where it should be in relationship to the front. The stamping is good and looks old. Does the rear of the case appear correct, and should it have the raised rectangle by the Delco-Remy or not? Which pulley fan is correct--the one that has 3 ribs on the wide vanes, or the one that has two and a flat space where the third would have been? Thanks for your input.

Mike-----


This is not a 1970 split ring (rear) alternator case half. This is from a later alternator. 1970 alternator had "7 fin" heat sink cooling, different Delco script, and a small slightly raised rectangle beneath Delco script.

Is it possible this configuration case half was used VERY late in the model year? Yes, I suppose it's possible but I don't think so.

[Bill L.]

Re: Correct 70 350 hp 1100990 alternator?

I will try and get some pictures of the 900 alt on my 70 350/350. It is as Joe described.

Bill

[David L.]

Re: Correct 70 350 hp 1100990 alternator?

Dave,
thanks. It's a 900, not a 990. My bad-typo.

Mike,

As per the 1970 AIM the LT-1 (350 c.i. SHP) engine uses the same alternator as the LS5 which is # 1100900, fan # 1966990, and pulley # 3846180 (3 3/64" dia.). However, my 1972 Corvette Parts Catalog (Sept. 1971) list alt. pulley # 1970831 (3 3/16" dia.) for the 70 Corvette w/SHP. As Joe mentioned the back of your alt. is not 1970 vintage.

Dave

[Terry M.]

Re: Correct 70 350 hp 1100990 alternator?

Mike,

As per the 1970 AIM the LT-1 (350 c.i. SHP) engine uses the same alternator as the LS5 which is # 1100900, fan # 1966990, and pulley # 3846180 (3 3/64" dia.). However, my 1972 Corvette Parts Catalog (Sept. 1971) list alt. pulley # 1970831 (3 3/16" dia.) for the 70 Corvette w/SHP. As Joe mentioned the back of your alt. is not 1970 vintage.

Dave

Dave,
I do not care what the AIM says. 1970 LT-1 uses 1100884 61A alternator. I can't tell you the pulley number from here at work, but I believe I have it in my references at home. I aklso know the correct LT-1 pulley when I see it. I have had it on my list to go look at the rear case on the alternator for the square cited above -- but this thread came after the temperature dropped, and work has been tking more of my time than usual. I'll get there one of these days.

[Bill B.]

Re: Correct 70 350 hp 1100990 alternator?

Pictures 3 and 4 don't seem to be the same alternator

[David L.]

Re: Correct 70 350 hp 1100990 alternator?

Dave,
I do not care what the AIM says. 1970 LT-1 uses 1100884 61A alternator. I can't tell you the pulley number from here at work, but I believe I have it in my references at home. I aklso know the correct LT-1 pulley when I see it. I have had it on my list to go look at the rear case on the alternator for the square cited above -- but this thread came after the temperature dropped, and work has been tking more of my time than usual. I'll get there one of these days.

Terry,

I'm sure that you are right about the alt. number.
Does the 70 Corvette LT1 use the same alt. pulley as the 70 Z28, GM # 1970831 (O.D. = 3.2", I.D. = 1.4")? Enclosed is a photo of a NORS 3844100 alt. pulley (1990's vintage, O.D. = 3.2", I.D. = 1.6", width measures 0.83") that replaced the 1970831 pulley in Nov. 1984. The finish on is a yellow/gold instead of the zinc type finish.

Dave

[Joe L.]

Re: Correct 70 350 hp 1100990 alternator?

This is purportedly an original alternator. Supposedly recently taken off a running 70. My suspicions are raised when I see that the rear case is clocked 90 degrees off from where it should be in relationship to the front. The stamping is good and looks old. Does the rear of the case appear correct, and should it have the raised rectangle by the Delco-Remy or not? Which pulley fan is correct--the one that has 3 ribs on the wide vanes, or the one that has two and a flat space where the third would have been? Thanks for your input.

Mike------


Attached is a photo of the rear of the split ring end case of an NOS GM #1100543 alternator [not for sale]. This unit was manufactured on July 3, 1970 for the 1971 model year. This case half is similar to the 1970 I described above except it does not have the "7 fin" heat sink. If any split ring case half other than the one I described in my above post was used for 1970, I would expect it would have been this one. Note the differences from the one you pictured.


DSCN2815.jpg

[Bill L.]

Re: Correct 70 350 hp 1100990 alternator?

Dave,
I do not care what the AIM says. 1970 LT-1 uses 1100884 61A alternator. I can't tell you the pulley number from here at work, but I believe I have it in my references at home. I aklso know the correct LT-1 pulley when I see it. I have had it on my list to go look at the rear case on the alternator for the square cited above -- but this thread came after the temperature dropped, and work has been tking more of my time than usual. I'll get there one of these days.

Yep! What Terry says.

[Bill L.]

Re: Correct 70 350 hp 1100990 alternator?

Hi Mike,

This is a pic of the restored 900 Alternator in my 70 with 350/350.

900 Alt 2.jpg

[Bill L.]

Re: Correct 70 350 hp 1100990 alternator?

Hi Mike,

Got a couple more pics showing script with rectangle below and one showing the 7 fin heat sink.

Bill

script 900 Alt.jpg Heat Sink 900 Alt.jpg

[Mike E.]

Re: Correct 70 350 hp 1100990 alternator?

Thanks for the help! Your (plural) input helped me determine that the piece in question is correct and original, but with the rear case clocked 90 degrees. If I provided confusion by picturing two different alternators for comparison, my apologies.

[Terry M.]

Re: Correct 70 350 hp 1100990 alternator?

Terry,

I'm sure that you are right about the alt. number.
Does the 70 Corvette LT1 use the same alt. pulley as the 70 Z28, GM # 1970831 (O.D. = 3.2", I.D. = 1.4")? Enclosed is a photo of a NORS 3844100 alt. pulley (1990's vintage, O.D. = 3.2", I.D. = 1.6", width measures 0.83") that replaced the 1970831 pulley in Nov. 1984. The finish on is a yellow/gold instead of the zinc type finish.

Dave

I don't have measurements, and when I decide to brave the cold I am more likely to take a photo than measurements -- but that looks about the right configuration, much as one can tell from a photo. The finish, however, looks yellow gold, and original 1970 LT1 alternator pulleys were silver. Of course that yellow hue in the photo could be from the lighting. I know everyone likes photos, but I don't for the above reasons.