Date codes for 1970 LT-1 Smog Pumps

[Charles S.]

I have a 1970 LT-1 with a May build date and am in the process of trying to make sure I have a correctly dated smog pump. I have the Judging Manual, which helps, but want to make sure. I currently have two smog pumps both bearing casting numbers 7801149. They are also coded from left to right as follows: Pump 1: 57 D20
Pump 2: 306 D59
Also, can you please clarify what color/finish the cast smog pump mounting bracket should be for my car. One that I have is black while the other is orange. I would also like to know whether the pulley for this pump can be painted black without a significant point deduction. My pulley is from Paragon and came that way (black).
Thanks in advance for the assistance.

[Joe L.]

Re: Date codes for 1970 LT-1 Smog Pumps

Charles-----

The numbers that you have provided are casting numbers from the pump backing plate. They do not positively ID the pumps that you have, although the 7801149 is the number used for 1970 pumps (but, also for other year pumps, too).

The date code for smog pumps will usually be found on a "half-moon" shaped machined surface on the pump's aluminum body. The date is usually a 6 character stamping. The first 3 digits are the consecutive day of the year and the fourth digit is the last digit of the year. The last 2 characters denote shift and pump model code.

The cast bracket for your engine was installed at the engine plant and is painted engine orange.

Original pullies were usually finished with black phosphate finish. However, some may have been just semi-gloss black. Your application requires a pulley and a steel spacer between the pulley and the pump.