71 LT1 Alternator 1100950
I have the incorrect 71 LT1 alternator. I need help identifying the correct part. I know the part number is 1100950 but I've been told there is an open face design. Basically I am not sure what I need. I have found some out there with the correct date codes but I am not familiar with the part. AX emissions label 3994020. 074 carb, OG10 starter, swedged exhaust, single fuel line, 101698Vin. Can someone also tell me the correct time limits on parts before the car is built and when aproximately my car was built? Black book states between Aug and Sept 70 but I would like to narrow down. I am a new member and have many questions and would really appreciate the help. Thanks, Chuck
-
-
Re: 71 LT1 Alternator 1100950
Figuring out when your car was built is pretty simple on a C3. The date the trim tag was stamped and attached to the body is usually 1-2 days before the car was completed and rolled off the line.
The date is located in the upper right hand corner of the tag and will be a single alpha character (the month) followed by two digits representing the days of the month. With the VIN derivative you've given your tag might read B15 or similar.
Some engine components will predate the assembly date of the car by a few weeks and in rare circumstances up to six months. Other engine components will predate the assembly date of the engine by a similar margin all depending whether the engine plant or the car plant installed them. In the case of the alternator, I beleive it was installed at the car assembly plant.
Hope this helps. -
Re: 71 LT1 Alternator 1100950
Chuck-----
Under NCRS and NCCB judging guidelines, dated components must be within 6 months prior to the car's build date to be considered "date correct". The build date of your car is sometime around the middle of September, 1970. You can find the body build date on your trim tag. It will be stamped near the top of the plate. In your case, it should be a "B" (indicating September) followed by 2 digits (representing the day of the month).
The alternator should have a stamped date preceding that date by no more than 6 months. In actual practice, one would usually find a date within 2 weeks to 6 weeks prior, but up to 6 months is allowed. So, you should have an alternator manufactured sometime between the middle of March, 1970 and a few days before your car was built.
Attached are photos of an NOS GM #1100543 alternator which was manufactured in July, 1970. It will have the exact same case configuration as the GM #1100950, so you can use this as a reference to what you should be looking for as far as configuration goes. I believe that only the clocking is different between the 1100543 and the 1100950 (and, that's the reason for the difference in part number).In Appreciation of John HinckleyComment
-
Re: 71 LT1 Alternator 1100950
BO4 Is there a part number for the rear case and fan number that i could get, what dia pulley would be correct and are the repo availibly. Can an aim help me with some of these questions. One other question i have is the carb studs seem to be long approx 1 inch above the base with the carb in place and where the nuts installed with washers, holley 4801. Thank ChuckComment
-
Re: 71 LT1 Alternator 1100950
I have been told that the 1100950 alternators were produced in batches maybe only once or twice per month. I am aware that 0H12 (August 12, 1970) was a production date for these in early 71 model year. I am not sure what other production dates for 1100950s close to that time (someone out there probably knows many of the possible dates).Comment
-
Re: 71 LT1 Alternator 1100950
Chuck-----
If you are referring to the split ring end (i.e. rear) alternator case half, it was GM #1846523. However, this number is not usually found anywhere on the part and it's long-since GM-discontinued. Nevertheless, this frame half is usually not that hard to find. The drive end case half you need with the correct configuration and stamped numbers may be very hard to find, though.
The alternator fan was most likely either GM #1966990 or GM #800594. The 1966990 is long-since discontinued, but not too hard to find. The 800594 was still available from GM the last time I checked. No part numbers are found on any of these fans.
The pulley was originally GM #1970831. This is a machined steel pulley of 3-1/8" OD. It is zinc plated. Good reproductions are available.
The carburetor studs were originally 1-7/8" in TOTAL length. So, if you remove one and measure it to be 1-7/8" in total length, then you have the correct length studs. From what you describe, I would say they are correct in length.In Appreciation of John HinckleyComment
-
Re: 71 LT1 Alternator 1100950
950 alternators are very rare an the older dates are very hard to find. They were made in batches so many are the same date for each year they were used. I was told the 950's were used only on Corvette's so this is why they are hard to find.Lyle
Comment
-
Re: 71 LT1 Alternator 1100950
How do i tell the engine assembly date and was the alt installed at the assembly plant for the car or with the motor. I have found h and g alts that i can get there fairly pricey but i dont mind spending the money if im done with that part. ChuckComment
-
Re: 71 LT1 Alternator 1100950
Chuck, The engine assembly date will be stamped on the engine pad -- in front of the passenger side head V XXXX CGZ. Those four Xs will be the month and day of engine assembly, but you don't need to know that.
The alternator was installed at St. Louis, so the date needs to be within six months before the body assembly date on the trim tag. A hint: Any part shown in the Assembly Instruction Manual (AIM) with a part number was installed at St. Louis. You do have an AIM for the year of your car, right?TerryComment
-
Re: 71 LT1 Alternator 1100950
No aim yet but i will get one asap. What about the washers under the carb nuts and was the a heat shield. How near can a part be to the build date and still look right. ThanksComment
-
Re: 71 LT1 Alternator 1100950
Chuck,
There shouldn't be any heat shield. But you will need the carburetor insulator. Try Doc Rebuild for that piece.Comment
-
Re: 71 LT1 Alternator 1100950
Warren is right about the insulator. Holley carbs used nuts with a built in washer -- no additional washer needed.TerryComment
-
Re: 71 LT1 Alternator 1100950
Now i Know why my carb studs look so long because of the thick insulator. If i can get this last question answered ill leave every alone. How close to the car build date can parts be and still look correct. ThanksComment
-
Re: 71 LT1 Alternator 1100950
Thanks for the info i Know now that it can be 6 months but from the date it was built does it need to be a week a day to six monthsComment
-
Re: 71 LT1 Alternator 1100950
Chuck--
You need to understand the production process. It was not a first-in, first-out system. Most of the components were manufactured somewhere else, and transported to St. Louis for assembly. Most components would be questioned if they were dated a day or two ahead of the assembly date of the car. Your car is interesting because it was born about 700 cars (a week or so) before a two-month GM strike (Sept-Nov. 1970).
It sounds like although you are a newbie here, that you have a good eye for what questions to ask--I think getting the Restorer master CD would be good for you. I have written 3 articles over the years on component dating, as well as two on 71LT-1 cars--you'd benefit from that.
Regards,
Mike ErnstComment
Comment