Pulley #3850979

[Edward D.]

I've looked this up in archives, but no satisfactory answer. 1965 JG and AIM both call for water pump pulley 3850979 for a car with C60 and N40. Does anyone have a pulley thus marked in a 65? If so got a pic or measurement?
What I have is a 3848904 pulley that is 6-9/32". The JG calls this pulley out as an alternate for the L76 engine,not the L79. When used with the 5-3/4" OD compressor pulley the 3849085 belt is too long. If the L76 compressor pulley 6-3/8" OD is used the belt is right length. But, the JG wants the smaller pulley on the compressor for the L79. I also have a 3770245 pulley that's 7-1/8" and is used on most L79s, but not with C60 per the JG. The belt also fits using this pulley.
So the question is, what size is the 3850979? I can find no technical info on it. Has anyone actually seen one or have one? This is not about making it work, I can do that. This is about judging points on a high end restoration in progress. Car is an original L79, C60, N40 coupe built 1/29/65.

Update: There are two possible belts 3849085, 56.75" long, used from 2/65 onward. 3847705, 57.50" long used 1964-2/65. I appear to have the longer 7705 belt. I'm going to get the shorter 9085 belt and it may cure the belt size issue using the smaller 8904 pulley.
But the main question remains: DOES ANYONE HAVE OR EVER SEEN A 3850979 PULLEY AND WHAT OD IS IT?

[Joe L.]

Re: Pulley #3850979

I've looked this up in archives, but no satisfactory answer. 1965 JG and AIM both call for water pump pulley 3850979 for a car with C60 and N40. Does anyone have a pulley thus marked in a 65? If so got a pic or measurement?
What I have is a 3848904 pulley that is 6-9/32". The JG calls this pulley out as an alternate for the L76 engine,not the L79. When used with the 5-3/4" OD compressor pulley the 3849085 belt is too long. If the L76 compressor pulley 6-3/8" OD is used the belt is right length. But, the JG wants the smaller pulley on the compressor for the L79. I also have a 3770245 pulley that's 7-1/8" and is used on most L79s, but not with C60 per the JG. The belt also fits using this pulley.
So the question is, what size is the 3850979? I can find no technical info on it. Has anyone actually seen one or have one? This is not about making it work, I can do that. This is about judging points on a high end restoration in progress. Car is an original L79, C60, N40 coupe built 1/29/65.

Update: There are two possible belts 3849085, 56.75" long, used from 2/65 onward. 3847705, 57.50" long used 1964-2/65. I appear to have the longer 7705 belt. I'm going to get the shorter 9085 belt and it may cure the belt size issue using the smaller 8904 pulley.
But the main question remains: DOES ANYONE HAVE OR EVER SEEN A 3850979 PULLEY AND WHAT OD IS IT?

Edward------

If the GM #3850979 pulley ever existed, it was never available in SERVICE. The only pulley specified from the very beginning for the application you mentioned was the GM #3848904.

Curiously, there were once waterpump pulleys of GM #3850977 and 3850978. However, these were applicable to passenger car applications, not Corvette. Still, that series "implies" that this series might have had a 3rd member of GM #3850979. Or, it could have been planned but "stillborn".

By the way, the L-76 and L-79 generally use the same pulley systems.

[Edward D.]

Re: Pulley #3850979

Thanks Joe. I think the 8904 pulley we have is the original for the car so we will use it. I think you are correct in that the 979 pulley was likely never used. Maybe in the future those responsible for the JG can extend the footnote allowing the 979 for the L76 to the L79 application as well.

[David L.]

Re: Pulley #3850979

My 1965 Chevrolet Parts Catalog (Effective Oct. 1964) lists GM # 3848904 for the 64-65 Corvette (C.A.C. w/Sp. H/Per.) and described as follows: "double (6 9/32 O.D.)(stamped 3848904)".
My 1964 Chevrolet Parts Catalog does NOT list GM # 3848904 NOR does it list GM #3850979. GM # 3850979 is not listed in my vintage Chevrolet Parts Catalogs or Chevrolet Parts History. However, GM # 3850979 is listed in the 1964 Corvette AIM (C60 w/L76).
Dave