Big Block Chevy smog ID help??????

[USER-3965175]

Your smog pump assembly is for 1969 307 and 327 engines with standard transmission. The "293" diverter valve is what makes the assembly for 307 and 327 engines - "295" diverter valve was used on 302 and 350 engines with standard transmissions

The date is missing the first number which would be "0" - "1" or "2" so the date could be "069" or "169" or "269" the day of assembly and "9" is the year - 1969 the last number "1" is for the shift - 1st shift and "S" is for Chevrolet classification

USER-3965175

[Kurt S]

http://www.camaros.org/emissions.shtml#pumps has more info.

I doubt the "1" in the date code is the shift. I've never seen a 2. Probably a plant code.

I don't think I mentioned it in the article, but there's a casting date behind the fan.

[BARRY]

1 is for chevrolet divission and S is for saginaw

[USER-3965175]

Shown in the pics below are three pump assemblies - the first one is the Buick Olds style pump stamped with the "R" code for Buick - Olds and the second style pump is the Chevrolet pump stamped "S" for Chevrolet - the third assembly is for Chevrolet pump with relief valve and is coded "Y" and was
used on 1969 427 Impalas with the "RED" Pressure Relief Valve

Note the pump stamped "R" for Buick and Olds is threaded on the bottom mounting position without the metal spacer between the front housing and rear backing plate and is not threaded at the top mounting position - short bolt is used at bottom threaded position and the long bolt is used on the non threaded top position - I removed this pump from a 1968 Buick grandma type car at the junk yard

The Chevrolet pump stamped "S" for Chevrolet is just the opposite - The bottom position is not threaded and uses a metal spacer between the front pump housing and rear backing plate and uses the long bolt - the top position is threaded and uses the short style bolt

ALL 1968 Chevrolet and some special application 1969 Chevrolet pump assemblies with the Pressure relief Valve on top of housing are stamped with a different code such as "Y" used on the 1969 427 impala dated smog pump below

There some codes such as "Z" and a few others stamped on housings that I have found but were already removed from the vehicle and I don't know what applicaiton they are for

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