'69 2-Groove Crankshaft Pulley with AC

[Kevin S.]

There is a conflict of information that I am trying to sort out regarding the 2-groove crankshaft pully for an L-46 350/350 with PS, PB, and AC.

My TIM&JG 6th edition on page 172 says, "all engines have a stamped-steel two-groove crankshaft pulley dip-painted semigloss black. 327's and 350's use 3850838 and all 427's use 3921923BM." Book goes on to say, "air-conditioned cars with power steering use an additional semigloss dip-painted stamped-steel pully, part number 3751232, secured with the existing bolts". My additional pulley is correct and the PN matches the NCRS book so I'm good there.

My AIM book on page 329 for air conditioning compressor, fan belts & pulleys, UPC C60 C1, item 9 in the parts listing at the top of the page shows 3911013, which is what I took off the car.

I have both two-groove crankshaft pulley PN's to put back on the car. Which one is correct for an early build 1969 350/350 with AC? I sourced PN 3850838 thinking that if I had to go one way or another that I would follow the TIM&JG.

Kevin
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[Kevin S.]

Is anyone able to clarify the discrepancy between the AIM and the 68-69 TIM&JG regarding the 2-groove crankshaft pulley?

AIM says the correct pulley is PN 3911013 BW

TIM&JG says the correct pulley is PN 3850838 BG

I know that the 2-groove pulley is judged but I do not recall being able to see the part number once the pulley is attached so maybe the PN stamp is a mute point. There is a 1/2" difference in the outside diameter between the two different pulleys.

[Patrick H.]

I know that the 2-groove pulley is judged but I do not recall being able to see the part number once the pulley is attached so maybe the PN stamp is a mute (moot) point. There is a 1/2" difference in the outside diameter between the two different pulleys.

Bingo!

You removed what you believe is an original part for your car, and it can't be seen.
I'd reinstall, and then send an email to Gary Bosselman with your findings.

[Kevin S.]

Thank you for your reply, Patrick. It is much appreciated.

I'll do that and send photos and my findings to Gary Bosselman.

Kevin

[Gary B.]

Looking through the AIM, 69 with AC, regardless of PS or not, regardless of engine size, used the 3911013 pulley.
If the car had PS and DID NOT have AC, it would have used a 3751232. AC over-rides other options, I believe.
I suspect the difference is in diameter. AC would be smaller to slow the belt speeds down ? (SFPM) Or do I have that backwards?
I've updated the TIM&JG accordingly.
Gary Bosselman

[Joe L.]

Looking through the AIM, 69 with AC, regardless of PS or not, regardless of engine size, used the 3911013 pulley.
If the car had PS and DID NOT have AC, it would have used a 3751232. AC over-rides other options, I believe.
I suspect the difference is in diameter. AC would be smaller to slow the belt speeds down ? (SFPM) Or do I have that backwards?
I've updated the TIM&JG accordingly.
Gary Bosselman

Gary------


I agree that the 3911013 is the correct crankshaft pulley for 300 hp or L-46 with C-60 with or without power steering. The 3911013 is a standard groove pulley and was primarily used for small block C-60 applications, Corvette and otherwise. In general 1969 L-46 used a deep groove pulley set EXCEPT when equipped with C-60. In that case, the pulley set reverted to the standard groove set. If the L-46 was equipped with both C-60 and power steering, then single groove standard groove pulley 3751232 was sandwiched to the front of the 3911013 and drove the power steering pump.

As I mentioned above, when not equipped with C-60 the L-46 used deep groove crankshaft pulley 3858533. This pulley was used with or without power steering and no add-on pulley was used. The remainder of the pulley set for non C-60 were deep groove.

300 HP engines without C-60 used standard groove crankshaft pulley 3850838, with or without power steering. If the car was equipped with power steering, single groove, standard groove pulley 3751232 was sandwiched to the front of the 3850838.

I should also mention that the 3911013 and 3850838 could be used interchangeably because the only difference is OD; pulley alignment with either is the same. Consequently, It's possible that St. Louis sometimes did do this but it is not what GM designers intended.. Since the crankshaft pulley essentially drives the rest of the pulley system, the only functional difference that would occur with either of these pulleys would be the speed that the rest of the pulley system would operate due to the diameter difference of the 2 pulleys.

[Kevin S.]

Hi Joe,
Thank you for the additional information regarding the 3911013 pulley for the 1969 L-46 engine with factory AC ( RPO C-60 ).

Hi Gary,
I'm happy to provide you with any photos you deem helpful. I have the OEM 3911013 pulley that I took off my car and restored and I have a new 3850838 pulley in it's original GM box untouched and in perfect original condition.


Kevin