Smog Pump Julian Date Decode
#21
Safety Car
AIR_1978 datecode.pdf
Last edited by hunt4cleanair; 12-07-2017 at 05:17 AM.
#22
Team Owner
Member Since: Jun 2000
Location: Southbound
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Last edited by Easy Mike; 12-07-2017 at 06:53 AM.
#23
Team Owner
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Location: Westminster Maryland
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Hi Larry,
"Thomas C. Van Flandern:"
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
I remember he was very good at knowing the date.
"Thomas C. Van Flandern:"
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
I remember he was very good at knowing the date.
Last edited by Alan 71; 12-07-2017 at 10:35 AM.
#24
Le Mans Master
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.
#25
Burning Brakes
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.
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.
#26
Le Mans Master
#30
#31
Racer
I agree with toylman.......179th day of 1973 or June 28. The GL broadcast code on your diverter valve is correct for a '73 as well.
Attached are pics of the AIR Pump and Diverter Valve from my'73 L-82/M-20, removed in 1974
1973 AIR Pump and Diverter Valve, removed in 1974
1973 AIR Pump stamp 61st day of 1973 or March 2 1973. Body build date is H23 or March 23
1973 Diverter Valve
Hope this helps, F2 Speedy
Attached are pics of the AIR Pump and Diverter Valve from my'73 L-82/M-20, removed in 1974
1973 AIR Pump and Diverter Valve, removed in 1974
1973 AIR Pump stamp 61st day of 1973 or March 2 1973. Body build date is H23 or March 23
1973 Diverter Valve
Hope this helps, F2 Speedy
#33
Melting Slicks
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.
#34
Racer
There is a '73 pump/diverter valve/hoses for sale on ebay for $395
https://www.ebay.com/itm/Corvette-Or...UAAOSwTh1gCEog
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.
The following users liked this post:
F2 Speedy (01-29-2021)
#35
Melting Slicks
The "S" stands for Saginaw
The Saginaw Division of General Motors manufactured the air pumps used on all domestic cars during 1970′s
Here is a good article about these pumps.
http://what-when-how.com/automobile/...em-automobile/
Last edited by PJO; 01-30-2021 at 10:36 AM.
#36
Burning Brakes
pump stamp
"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.
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.
#39
Le Mans Master
Last edited by avalonjohn; 01-30-2021 at 10:42 PM.