[GTOh!]

Hi all. I have a '67 GTO with the HO / 4 speed powertrain (WV Code) and I'm in the process of detailing the engine and under-hood area. I've seen broadcast codes on other GM pumps and am wondering if my WV engine originally had a code stamped on it. I recently saw a code stamped on a 1967 Corvette's pump and I've attached a photo to this thread.

Does anyone here know if my WV coded engine's AIR pump should have a broadcast code stamped on it? If yes, I'll appreciate any advice as to which letter code I need.

Many thanks!

[gto4ben]

The 7800307 "U" code pump was used on V8s. I don't recall a stamp on the pump like I've seen with "XB" codes on alternators but they may have been washed off many years ago, I'll have to look at my spare greasy ones to see if and where they stamped any codes.

[428ho4spd]

I've never seen an ink stamp on a '67 anti-backfire valve, the diaphragm "can" was just stamped with Holley. Here's a photo of the date & usage code on my original smog pump.

[gto4ben]

I checked my inventory of pumps and discovered that there is a stamping on a machined pad on the air pump housing. It consists of five digits and a letter. I believe the letter is the code that matches what I found in the 1967 GTO Assembly Manual. The numbers I found are:
03971U
19361U
36361U
16861A
22251A
04962C
I looked for any ink stampings similar to how they marked alternators. I didn't find any,

[gto4ben]

Here are my Julian to Calendar date conversions, including 428HO4SPD's. The dates make sense for pumps used in '66 and '67. I wonder what the digit before the letter code stands for (Shift?),

[428ho4spd]

I just found this in a Motor Trend article, the 1 or 2 is indeed a plant shift code....

The date code for the AIR pump is stamped on a pad on the side of the pump housing. The date code for this pump is 11901S.
1. The first three characters, 119, refer to the day of that year, this number is also known as the Julian Calendar Date. The Julian Calendar Date is the 365-day calendar with a continuous count of days in the year. So in 1970, 119 would equal April 29.
2. The fourth character, 0, equals the year. In this case, 1970.
3. The fifth character, 1, is the plant shift code. The 1967 AIR pumps were coded 1 or 2, and most 1968 and later pumps were coded 1. 1 equals first shift and 2 equals second shift.
4. The last character, S, is the configuration code of the pump. All 1967 Corvette AIR pumps are coded P. The 1968 AIR pumps with a pressure relief valve installed in the pump are coded Y. The 1968 AIR non-pressure relief valve pumps were coded Z. Most 1969 and later pumps without a pressure relief valve are coded S.

[60sstuff]

In 45+ years in the GTO hobby I’ve never seen a Black Ink Stamp on the 66-67 smog pumps.

Below is a very early ‘66 GTO pump and hardware with no ink stamp found.

[gto4ben]

I looked at all my AIR pump pressure relief valves, including two spares I removed from their housings, and could not find any codes stamped or inked. The poppet stops had different depths though. I measured the depth from the valve top to the inserted stop. The"U" coded pumps were deeper than the "A" and "C coded ones.

[428ho4spd]

And I found out that those relief valves make a hell of a racket when the anti-backfire valve diaphragm is bad.

[60sstuff]

Originally Posted by GTOh!

Hi all. I have a '67 GTO with the HO / 4 speed powertrain (WV Code) and I'm in the process of detailing the engine and under-hood area. I've seen broadcast codes on other GM pumps and am wondering if my WV engine originally had a code stamped on it. I recently saw a code stamped on a 1967 Corvette's pump and I've attached a photo to this thread.

Does anyone here know if my WV coded engine's AIR pump should have a broadcast code stamped on it? If yes, I'll appreciate any advice as to which letter code I need.

Many thanks!

The (WV code) in 1966 was obviously the Tri-Power with A.I.R. and I have a unit off a ‘66 showing what’s called a “intake air bleed valve” with the two letter ink stamp (HY) on the rear of valve.

I’m not sure what was used on the 66-67 Corvettes.

[428ho4spd]

Originally Posted by gto4ben

I looked at all my AIR pump pressure relief valves, including two spares I removed from their housings, and could not find any codes stamped or inked. The poppet stops had different depths though. I measured the depth from the valve top to the inserted stop. The"U" coded pumps were deeper than the "A" and "C coded ones.

Doing a quick search on eBay by part numbers, it appears that the relief valve and the plug were serviced separately.

[428ho4spd]

Originally Posted by 60sstuff

The (WV code) in 1966 was obviously the Tri-Power with A.I.R. and I have a unit off a ‘66 showing what’s called a “intake air bleed valve” with the two letter ink stamp (HY) on the rear of valve.

I do remember my old '66 having that ink stamp as well.

[GTOh!]

Happy Labor Day and thanks to all for posting outstanding information.

While I find it weird that similar pumps and valves were used across multiple GM brands, evidently, some used the ink stamp to identify build info and others didn't. I will not stamp my components as shown in the Chevrolet pump from my initial post here.

I also appreciate the Julian date info. I've printed it and added it to me restoration binder for further/future reference.

Thanks again!