66 Base engine alternator mounting

[Dave K.]

I purchased a new date coded alternator and replacement refurbed exhaust manifolds for my 66 base engine. I mounted the alternator bracket and alternator per the AIM. Noticed that the crankshaft and water pump pulleys are correctly in line but the alternator sits about a 1/4 in. too far to the rear for proper alignment of the fan belt. Bracket appears to have too wide an opening for the alternator and when the long bolt is tightened it bends the bracket inward, pushing the alternator up and back. I made a 1/8 long bushing from pipe and installed it between the alternator and the bracket at the rear of the alternator and it appears to have corrected the alignment. Originally, there was no bushing on this engine. I'm assuming that the bracket could be a little bent, and the tolerance stack up with the new ex. manifold and alternator could have all added up to give me this this problem?

Dave Kitch

[Joe L.]

Re: 66 Base engine alternator mounting

Dave-----

Make sure that the alternator mounting boss on the alternator (the boss with the hole in it on the bottom of the drive end case and through which the long bolt passes) has not been altered. This boss should be exactly 2" wide if it's as original.

[Dave K.]

Re: 66 Base engine alternator mounting

Joe,

Measured my new alternator boss - 1 7/8in. The service replacement alternator that was on when I bought the car measures 1 13/16 in. Neither are exactly 2 in. Spacer that I made is ~ 1/8 in.

Dave Kitch

[Joe L.]

Re: 66 Base engine alternator mounting

Dave-----

I believe that the GM #3846565 generator support is designed around the fact that the alternator mounting boss is 2" wide. So, if you are working with an alternator that, for whatever reason, has a thinner boss, a spacer will be required as you found out. None were ever used in PRODUCTION, though, as far as I know.