C-3 Smog pump pulley

[Leonard M.]

The '70-'72 JG and the Prince book list the 3917234 pump pulley for small blocks that came with the A.I.R. system. I have 2 x 3917234 pulleys (one on my '70) and both were removed from 1970 dated pumps. I have had 4 x 3917234 AL pulleys and all were removed from 1973 dated and newer pumps.
Question is; when did the 3917234 AL pulley come in being? I'm guessing they were factory installed, but when? I am guessing they are from a different manufacturer since they have slight differences. AL is 1/16" larger in diameter, 1/32" less V grove depth, Non "fluted" back edge and stamp is straight across with a P. I'm guessing they would Not have been installed on a '70-'71 pump.
The AL has original paint.

[Joe L.]

Re: C-3 Smog pump pulley

Leonard------


The GM #3917234 was first released for the 1968 model year. It was used through at least the 1976 model year for most, but not all, Corvette small blocks. It was also used for other GM applications. Original, assembly line pulleys and SERVICE pulleys manufactured at least through 1972 were usually phosphate finished.Later pulleys are often painted black. However, there may have been optional finishes specified so it's possible that some original pulleys were black-painted. I have not seen every pulley that was ever originally installed so I can't say for sure one way or the other.The spacer used on these pulleys was natural steel and several different thicknesses were used depending on small block engine application and pulley system.

[Gary B.]

Re: C-3 Smog pump pulley

Leonard,
Would you mind if I use a few of these pictures?
Gary Bosselman

[Leonard M.]

Re: C-3 Smog pump pulley

Thank you Joe. Any idea when the AL version showed?

[Leonard M.]

Re: C-3 Smog pump pulley

You are welcome to use any pictures I post. The black AL appears to be original paint. The gray one looks to be repainted.

[Joe L.]

Re: C-3 Smog pump pulley

Thank you Joe. Any idea when the AL version showed?

Leonard------


"AL" was the broadcast code for the pulley and, as far as I know, was always the broadcast code for the pulley. I do not know when the actual stamping of the code began. I expect that earlier pulleys without the stamped code had a sticker or ink-stamped "AL" code on them so that the assembly line workers knew which pulley to install.

[Leonard M.]

Re: C-3 Smog pump pulley

Thanks again Joe. I have looked for these pulleys and I have not seen the AL stamped version on '70 or '71. I was contacted by a collector in CT who said that the AL version showed in '72. Your knowledge of the finish adds to that thinking.