what is the correct dia. for 837 alt deep pulley

[deuce-less]

trying to match up the correct deep groove pulley for a 69 L-78 nova 837 alternator....

i have two, one is approx. 3 3/16 dia the other is 3 9/16 dia. inches, which one, if either is correct for the application?

thx, alan

[Mr70]

I have two original 837's here,and they both have the 3-3/16" OD pulley.

[deuce-less]

thx for the quick and accurate response

[3macs1]

[ QUOTE ]
trying to match up the correct deep groove pulley for a 69 L-78 nova 837 alternator....

i have two, one is approx. 3 3/16 dia the other is 3 9/16 dia. inches, which one, if either is correct for the application?

thx, alan

[/ QUOTE ]

I am glad you asked this question. I have some Nos 3 9/16 ones but have no idea what they fit. No part number on them like I have seen on some and the strange part is they have a 9/16" bore not 5/8"
Any ideas?? I thought I bought them for 66 l-72 about 27-28 years ago but am not sure

[Keith Tedford]

Try 3770245 Group 1.062 '67-'68 Z/28. May also be the same pulley on early solid lifter Chevies.

[3macs1]

Hi Keith:
Do you mean that alt pulley was used with the 2 groove water pump pulley you quoted the part number for??
Let me know
Thanks Joe

[Keith Tedford]

I was relaying information given to me. No guarantee that it is correct. I shouldn't be assuming anything. You know what that does. Other than the OD, it seems to be the same as the later small diameter pulley. They should interchange if you wanted to reduce alternator speed.

[3macs1]

Understand Keith. It is the 9/16 bore throwing me.I thought the GM alts were 5/8 bore but have not checked one in many years.