1969 427/400 AIR Pump

[David S.]

I have an early build date 1969 427/400 (Build date November 4th, 1968) S/N 6656 and need assistance determining whether or not the AIR pump on the car is correct. The AIR pump has the pressure relief valve mounted on the case. The NCRS Technical Information and Judging Manual states this is correct for 1968 and early 1969. What is considered early 1969? Any assistance is greatly appreciated.

Dave Sutherland NCRS# 36838

[Joe L.]

Re: 1969 427/400 AIR Pump

Dave-----

The 68-style AIR pump with integral pressure relief valve was used on some 69s. However, I've always thought that its 69 use was limited to L-88s/ZL-1s which also used the 68 diverter valves. 1969 diverter valves incorporated both pressure relief AND diverter ("dump") valve functions. 1968 valves incorporated only diverter valve function since the relief valve was built into the pump. However, the 68 style pumps can be used with 69 diverter valves (but 69 style pumps without pressure relief valve CANNOT be used with 68 style diverter valves without integral pressure relief function). In fact, in later SERVICE, the 68-style pump was used for all 68-71 applications. It's very possible, then, that in early 1969 PRODUCTION, the 68-style pump was used.

Anyway, none of this answers your question but does provide a little background on the pump/valve issue and I cannot tell you what defines "early" as far as the pumps go. However, these pumps usually have a date code stamped on them. It is usually found on the "short" rear cover mounting bolt boss on the main aluminum housing of the pump. This boss will have a "half-moon" shaped machining on it and there should be a very small stamping on this. The first 4 digits will be the julian date code----the first 3 digits will represent the day of the year and the 4th digit will be the last digit of the year. If you don't find it on the boss I described, look elsewhere for it on the main pump casting the last digit represents the shift and the "s" represents Saginaw Division which made the pumps).

Also, the diverter valve should have a stamped ID coding on it. Usually, this will be found on the cast main body of the valve and will include 5 digits representing the last 5 digits of the valve part number. These will also be very small characters, but if you look the valve over closely, you should see them.

Post what you find and maybe we can "zero-in" on whether everything seems original, or not.

[David S.]

Re: 1969 427/400 AIR Pump

Great information. The date code on the pump is 01081Y. My interpretation is the 10th day of 1968 (Jan 10th), first shift but I do not know what the "Y" stands for. Would this date be too old for a November assembly build date?
Thanx again.

[Joe L.]

Re: 1969 427/400 AIR Pump

Dave-----

The "Y" likely represents another Saginaw manufacturing plant. Saginaw had many manufacturing plants located in Saginaw, MI and elsewhere. When I said that the "S" represented the Saginaw Division, I should have said that it represented a CERTAIN Saginaw Division manufacturing plant. I gave a "generic" answer.

As far as the date code goes, you have it decoded correctly and it does seem too early for a November, 1968 built car. Certainly, it exceeds the NCRS "6 month rule" which is actually quite generous for most components. My 69 pump was manufactured about 2-1/2 months prior to my car's build date.

However, it's not beyond the realm of possibility. If the date had been well after the cars build date (e.g. if this were a GM SERVICE pump installed on the car at a later time), then that would make it "beyond the realm of possibility" as far as originality is concerned.

[Terry M.]

Re: 1969 427/400 AIR Pump *TL*

I believe the letter following the date code on the AIR pumps is the model of the pump. The 1969-1972 style pump has the letter S following the numbers and I believe the 1968 style with the built in relief valve is a Y model.
I often see the ID on the 1968 style pumps stamped on the housing itself adjacent to the half-moon machined area. The 1969-1972 style has the ID stamp in the machined area.

[David S.]

Thank You NM *NM*