[Terry M. Hunt]

Attached pics show cast bracket that holds a/c compressor on 66 GTO and also a page from the 66 Pontiac A/C manual showing how this bracket is retained by two head bolts. Bolt A goes in the rear hole of the bracket. Bolt B goes in the front hole of the bracket. I don’t have the correct bolts for this bracket. In order to obtain them I need to know the length of each bolt, measured from the bottom of the hex head to the end of the bolt. Can somebody provide these dimensions?

[TXSTARFIRE]

The parts book lists a head bolt specific to A/C applications. P/N 538946 1/2-13X 4 5/8 inches. Description is Bolt, head comp. mtg. bracket and oil level tube. The other bolt must be a standard head bolt but I dont know the length.

[Terry M. Hunt]

That’s great info. Thanks for your help. Maybe somebody else can give me the length of the other bolt.

[hakansan]

There must be the same length on both bolts.

[hakansan]

Originally Posted by TXSTARFIRE

The parts book lists a head bolt specific to A/C applications. P/N 538946 1/2-13X 4 5/8 inches. Description is Bolt, head comp. mtg. bracket and oil level tube. The other bolt must be a standard head bolt but I dont know the length.

In my book it says 5-5/8" not 4-5/8".

[TXSTARFIRE]

Originally Posted by hakansan

In my book it says 5-5/8" not 4-5/8".

You may be correct. 4-5/8 is the same length as other head bolts and I thought it would take a longer bolt by the looks of the bracket. My 7-73 MPC clearly shows that part number twice with both instances showing 4-5/8 inch length but I wonder if it is a misprint in the MPC. Does your MPC show that same number with the longer length, and what is the revision date on your MPC. A newer version of the MPC may have corrected an earlier misprint.

[Kenth]

From 1967 Pontiac Chassis Parts Catalog:

Bolt A #538946, 3/8" - 24 x 1/2" - 13 x 5 5/8"

Bolt B #518031, 1/2" - 13 x 4 5/8"

HTH

[TXSTARFIRE]

Roger that. I will update my MPC with the correct information.

[hakansan]

Originally Posted by Kenth

From 1967 Pontiac Chassis Parts Catalog:

Bolt A #538946, 3/8" - 24 x 1/2" - 13 x 5 5/8"

Bolt B #518031, 1/2" - 13 x 4 5/8"

HTH

The bolts must be the same length since the head of the bolt sits on the same height from the block.

[Terry M. Hunt]

One last update on this. I dug up the two different style bolts that retain the a/c bracket. Each one is 4 5/8 long. Did some more measuring and came up with the dimensions shown on the attached diagram reflecting this 4 5/8 length. It looks like a 5 5/8 length bolt would bottom out on either hole in the block, so I used 4 5/8 to attach my a/c bracket. Not sure why parts manual would specify 5 5/8.