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Smog pump 7817872 with Julian Date 201781S. What day and year? Does this belong to a corvette?
The 7817872 AIR pump was used from 1978 through 1980. See the attached for interpreting the date code format. Your pump was assembled in 1978 the 017 day of the year so a January 1978 pump.
Talk about a small world!
I sat next to Tom (we used to call him 'Boots' because he was so good at kickball) in the 4th grade.
His mother made the BEST peanut butter (smooth) and jelly (grape) sandwiches. Sometimes he'd give me a half... I can still taste them!
Regards,
Alan
While we can debate the date codes for much longer than a minute, we should not loose sight of the most important tidbit of information when it comes to smog pumps.....just because the casting number seems a good match AND the date code is in the range of acceptable....we still do not know if this pump will bolt up to the car in question!!!! The smog pumps were machined differently for every application. A Cadillac smog pump is machined differently from a Corvette smog pump or an Oldsmobile smog pump. ALL have the same casting numbers and date code styles but the mounting ears are all machined in different places depending on original application.
The attached explanation for interpreting date stamps on pump bodies is really all a person needs to read the date and match a pump body to their car, but there is more to it if anyone cares. The numbers 7801149 and 7817872 are Not the (part or casting) number for the pumps, but are simply the casting number for the bolt on back of the pump body. The pumps themselves have their own casting number that can only be seen when the fan is removed. Here are 4 pump bodies with 3 different casting numbers. 2 are corvette (78 & 68) and 2 are Cadillac (69 & 72 same casting numbers). The 3 different cast # bodies would bolt on the same way, but the case configuration, relief valve or none and case machining are all different.
The Cadillac pump bodies are very similar to early corvette pump bodies, but do have a slight casting difference on the side where they were machined to mount the diverter valves direct with no elbow where the '68 corvette pump body was machined to accept a relief valve in that area and the '77 corvette (different casting) had no relief valve since the diverter valve acted as the relief.
The back cases also were machined differently for other model cars.
Also, the Cadillac stamps do not have a letter at the end. The other 2 have the S. I have an early Camaro pump with a Z.
Of course none of this matters if one went to an advanced university with emphasis on the sciences then your only concern would be to stay clear of the Giant Squirrel.
That I found. Nothing Julian about it but the bastardization of the nomenlature. Technically speaking (probably above many pay grades here), it has to be based on the Julian calendar to be truly Julian. Should be obvious to the most casual observer.
It does thanks for the replies, any idea on its value ? my car is a 390/427 and Im looking for the smog system for it if anyone has some parts for a BB
If there is a first letter, it is for the assembly line. The next three numbers are Julian date; the fourth number is the last digit of the year; fifth number is the shift, and the last letter shows the model of the pump. Pumps built early in the year have been seen containing no zeros at the beginning of the Julian date. For this reason, sometimes there are not five numbers in the stamping.
It does thanks for the replies, any idea on its value ? my car is a 390/427 and Im looking for the smog system for it if anyone has some parts for a BB
There is a '73 pump/diverter valve/hoses for sale on ebay for $395
It is clean looking like yours, F2 Speedy. There are others listed with varying prices. This would be a good starting point. Adjust your pricing up or down as you see fit, of course.
"If there is a first letter, it is for the assembly line...the last letter shows the model of the pump"
It is possible, but doubtful that that unusual first character stand for the assembly line. You were correct the first time regarding the S in the stamp "The "S" stands for Saginaw" The cast S on the case indicates Saginaw, not the S in the stamp as there are other letter that were used besides S This is from a 2013 NCRS post written by Joe Lucia The alpha character at the end of the series represents the pump model.
1966-67= "A" (and, possibly, other codes, too)
1968 (GM #7803947 with relief valve)= "Y"
1968 and 1969 L-88/ZL-1 (GM #7806686 with relief valve)= "S"
1969-74 (GM #7803948 no external relief valve)= "S"
1975 (GM #7817575 no external relief valve)= "S"
1976-78 (GM #7817809 no external relief valve; different configuration than 69-75)= "S"
The first 3 digits of the stamped code represent the julian date. The 4th digit represent the last day of the year. The 5th digit may be a shift identifier. The final alpha character is pump model.
I cant find any stamping in the diverter valve, unless its under where the muffler clips on ?
It is on the flange well below the muffler (or should be), above where it bolts on. I will try to find a picture as an example. The stamping may be faint and hard to see.
Last edited by avalonjohn; 01-30-2021 at 10:42 PM.
12-07-2017, 05:15 AM
