66 L79 pulley help

[Terry L.]

Hi, I have a 66 L79, the crank pulley has a numbeer of 3850838 BG and the judging guide has that number but no BG after the number, the water pump pulley is the same way with a 3890419 CT, I ordered a set of GM restoration belts and they are to small using these pullies, I have a crank pulley that is 3744043BA that is smaller and when I put that pulley on both belts fit. what do I need to do to fix this? Thanks for all your help, Terry

[Joe L.]

Re: 66 L79 pulley help

Hi, I have a 66 L79, the crank pulley has a numbeer of 3850838 BG and the judging guide has that number but no BG after the number, the water pump pulley is the same way with a 3890419 CT, I ordered a set of GM restoration belts and they are to small using these pullies, I have a crank pulley that is 3744043BA that is smaller and when I put that pulley on both belts fit. what do I need to do to fix this? Thanks for all your help, Terry

Terry-----


Does your car have C-60? If not, the 3850838 crank pulley and 3890419 water pump pulley are not the correct ones.

[Terry L.]

Re: 66 L79 pulley help

Yes, sorry it does have AC,

[Joe L.]

Re: 66 L79 pulley help

Yes, sorry it does have AC,

Terry------


In that case, the GM #3850838, with or without suffixing broadcast code, and GM #3890419 waterpump pullies are the correct ones for your application. For the alternator belt to fit right the alternator pulley has to be right, too. It was GM #3846180 and 3-3/64" OD.

The original alternator belt was GM #3798498 and was 3/8" X 57.5". A GM #3848253 should also work.

The original compressor belt was GM #3847705 and was 15/32" X 57.5". A GM #3888404 should also work.

There have been reports of reproduction fan belts of the supposedly correct part number which do not fit properly. However, neither of the belts in question here are captive belts which have no adjustment. So, even if they are "off" a little from the originals, they should still fit OK.

[Terry L.]

Re: 66 L79 pulley help

Hi, thanks for your help, my alt pully does not have a number on it, so I will check the size. The letters behine the part number, do they mean anything and is it ok that they are there? Thanks Terry

[Joe L.]

Re: 66 L79 pulley help

Hi, thanks for your help, my alt pully does not have a number on it, so I will check the size. The letters behine the part number, do they mean anything and is it ok that they are there? Thanks Terry

Terry-----


The two alpha character code suffixing the part number is a broadcast code. This was used to enable line workers to quickly identify the correct part for a particular car. Many GM pullies have the broadcast code but some do not, including original pullies. Also, after a particular pulley is no longer used in PRODUCTION, the broadcast code may be dropped from SERVICE pullies. However, many times it remains on SERVICE pullies.