7817872 smog pump 1975?

[Peter S.]

From previous posts (a la Joe Lucia) I was informed that the 7817575 (with a backing plate casting of 7801149) was the correct pump for all 1975 corvettes.

A fellow on the corvette forum is selling the following smog pump with a backing plate casting of 7817872. The date code on the pump is August 28th, 1974 (24041, the pump model code is hard to see). Another previous post by Joe Lucia states this casting was used in '76 and later applications, including the corvette.

The seller is the original owner of the 1975 corvette in which he physically removed the pump himself in 1977.

A couple of questions:

1. Am I reading the date code incorrectly? Typical format is DayDayDayYearShift. Is this a 1984 service replacement pump that the owner may be fuzzy on where his pump came from?
2. Any known 7817872 pumps on 1975 corvettes? Is the date code (if 1974) too soon for 1975 production?
3. Anything in the pictures that would indicate that this is NOT what the owner claims (e.g. diverter valve elbow)?

[Joe L.]

Re: 7817872 smog pump 1975?

Peter------


It may be that the pump changed sometime during the model year. According to GM parts information, the GM #7817575 was used for the entire 1975 model year. Unfortunately, the 1975 AIM is "cut off" in the area of the pump part number (at least, in the copy I have). However, it appears from what I can see that there were 2 revisions of the part number during the 1975 model year I believe the first revision says "was 7803948" which was the 1969-74 AIR pump. The 2nd revision is illegible in the revision block at the bottom of the page. It MAY say "was 7817575". In that case, I would expect the "cut-off" part number would be 7817809, the 1976-78 pump. The pump you have pictured appears to me to be exactly that----a GM #7817809 pump. The 7817575 pump has a different backing plate and different pump body. I may have pictured an NOS GM #7817575 I have in the earlier post.

The diverter valve elbow appears to me to be a GM #3951346. This was used for later 1975 whereas early 1975 used the GM #3947728, the same used for 1969-74.

I believe the pump in the photo is very likely the original pump for this 1975. Do you know what the build date of the car it came from is?

[Peter S.]

Re: 7817872 smog pump 1975?

Hi Joe,

Unfortunately the seller sold the car long ago and has had the pump sitting around. No clue on the build date or the VIN.

Here was the previous thread where we discussed the 7817575 with your pictures: https://www.forums.ncrs.org/showthre...7575-smog-pump

If this was for a "late" 1975 corvette, I don't see how the date code with jive with this fact.

My '75 is a late car: K01.

[Joe L.]

Re: 7817872 smog pump 1975?

Hi Joe,

Unfortunately the seller sold the car long ago and has had the pump sitting around. No clue on the build date or the VIN.

Here was the previous thread where we discussed the 7817575 with your pictures: https://www.forums.ncrs.org/showthre...7575-smog-pump

If this was for a "late" 1975 corvette, I don't see how the date code with jive with this fact.

My '75 is a late car: K01.

Peter------

"Early" and "late" are relative terms and I really have no idea when "early" ceased and "late" began with respect to 1975 AIR pumps. There may even be three pumps that were used during the model year. If so, though, the first two were identical with respect to external configuration.

As I mentioned in the previous post, it would be nice to hear from folks with original 1975's.

Also, does anyone have a 1975 AIM which does not have the part number for item #1 (the AIR pump) "chopped off" and one which has a completely readable revision block on the bottom of the page (UPC 6T, Sheet 1)?

[Ruedi K.]

Re: 7817872 smog pump 1975?

I also have a 7817872. It lay in the attic for a very long time. Once I tried to sell it on Ebay at a very low price, nobody was interested

It was not from my 70 Corvette, I couldn't find out of what car it was, maybe somewhere between 1974 and 1980.
DSC01646.jpgDSC01653.jpgDSC01656.jpg

[Brian G.]

Re: 7817872 smog pump 1975?

Here is the pump on my wife's car that she's owned since April '76. January '75 built car.

Joe, Item #1 is MIA in my AIM too.

[Jim T.]

Re: 7817872 smog pump 1975?

I also have a 7817872. It lay in the attic for a very long time. Once I tried to sell it on Ebay at a very low price, nobody was interested

It was not from my 70 Corvette, I couldn't find out of what car it was, maybe somewhere between 1974 and 1980.
[ATTACH=CONFIG]50742[/ATTACH][ATTACH=CONFIG]50743[/ATTACH][ATTACH=CONFIG]50744[/ATTACH]

I believe the only 1970 Corvettes with the air pumps were the LT-1 and the ZR-1. My 1970 350/300 turbo 400 did not have one when new.

[Peter S.]

Re: 7817872 smog pump 1975?

Great responses, I'm glad to see others chiming in.

Brian, would you be able to take a picture of the date code?

[Brian G.]

Re: 7817872 smog pump 1975?

Peter, I won't be able to get a picture until spring.

[Joe L.]

Re: 7817872 smog pump 1975?

All------


Despite the problems with the relevant page of the 1975 AIM, I think we can glean this much information from that page:

1) While the part number or revision numbers cannot be seen, it can be seen that there were two revision numbers associated with the part number, whatever it was. The bottoms of the circles surrounding the revision numbers can just be seen;

2) The revision block at the bottom of the page shows that there were three revisions to the page, numbered 1, 2, and 3;

3) The number 2 revision was some sort of a torque revision, so it cannot apply to the AIR pump. Therefore, revisions number 1 and 3 must be the ones that apply to the AIR pump;

4) Revision number 1 states "was 7803948 pump" and is dated 11-7-74. The 7803948 was the 69-74 pump. Apparently, it was used for early 1975. The change would have occurred sometime after 11-7-74. 2 weeks to 2 months would be typical;

5) Revision number 3 would have been another change to the pump part number. Most of this line of the revision block is completely illegible. However, the date of 4-5-75 is quite clear. It's my guess that what this line said is "was 7817575 pump". If so, the 7817575 pump was used from ABOUT 11-7-74 until ABOUT 4-5-75, at least according to the AIM;

6) I also expect that the final part number for the pump shown as item #1 was 7817809. If so, this pump would have been used from ABOUT 4-5-75 until the end of 1975 production. I realize that this is all somewhat speculative. However, we pretty much know that there were two revisions to the 1975 AIR pump part number. We know that the original pump used from the start of production was 7803948, per the revision block. There were 2 following pump part numbers and the only possible numbers are 7817575 and 7817809. We also know that the GM #7817575 was the pump shown as the SERVICE pump for 1975 only in 1975 editions of the P&A catalog.

[Peter S.]

Re: 7817872 smog pump 1975?

Joe,

I have contacted Mid-America and they will be getting me the part number listed in the AIM. They said they should have it since it is their border that is cutting off this data.

They will also check on Revision 3.

Thank you for all this information.

One item I am still stuck on is that the pump this gentleman is trying to sell to me has an August 1974 date code. If this is, indeed, the pump used for '76+ and the possibly for late 1975, how does it have a 1974 date code? This clearly wouldn't be acceptable for NCRS judging.

Peter

[Joe L.]

Re: 7817872 smog pump 1975?

Joe,

I have contacted Mid-America and they will be getting me the part number listed in the AIM. They said they should have it since it is their border that is cutting off this data.

They will also check on Revision 3.

Thank you for all this information.

One item I am still stuck on is that the pump this gentleman is trying to sell to me has an August 1974 date code. If this is, indeed, the pump used for '76+ and the possibly for late 1975, how does it have a 1974 date code? This clearly wouldn't be acceptable for NCRS judging.

Peter

Peter-----

I agree that the August, 1974 date code implies that, if original, it was installed on this car quite a bit earlier than what I have described above. However, there are several possibilities:

1) It's very possible that the pump was manufactured in August, 1974 but not installed on a car until later 1975. This type of thing did happen and for a variety of reasons. Just because it's outside the NCRS-accepted "6 month rule" does not mean that it could not have happened.

2) It's also possible that the pumps were installed before the dates that were in the AIM. That would be very unusual but it could have happened.

If you can get a better copy of that page of the AIM I'd like to see it.

[Peter S.]

Re: 7817872 smog pump 1975?

Peter-----

I agree that the August, 1974 date code implies that, if original, it was installed on this car quite a bit earlier than what I have described above. However, there are several possibilities:

1) It's very possible that the pump was manufactured in August, 1974 but not installed on a car until later 1975. This type of thing did happen and for a variety of reasons. Just because it's outside the NCRS-accepted "6 month rule" does not mean that it could not have happened.

2) It's also possible that the pumps were installed before the dates that were in the AIM. That would be very unusual but it could have happened.

If you can get a better copy of that page of the AIM I'd like to see it.

Joe,

If MAM does give me a copy of the original, I will gladly pass it along. My guess is they will probably read them aloud to me, or send me the lines in an email. Let's hope for the original copy!

I do not disagree with any of your points above, but neither would be seen as "typical" and for us point counters we might be up the proverbial creek.

[Peter S.]

Re: 7817872 smog pump 1975?

Joe,

I spoke with "Frank" the technician at Mid America, and unfortunately they do not have a copy without the border. So, their part number for item #1 is also covered. I do find it highly unfortunate since my K01 car would have the last model pump used. Their copy is also illegible for the #3 revision.

At this point, you have made a good case that my car would have possibly come with the 7817809 pump. I will try and find other end-of-production '75s that still have their original A.I.R. pump.