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67gtocharlie · 02-05-2003, 08:10 AM

I need the specifications (part #?) for the two bolts that attach the A/C bracket (the cast one that bolts on the SIDE of the head, to the front two head bolts). It appears that the rear bolt is a stud and the front one is a bolt. I have 6X heads on a '69 400 engine in my 67 GTO.
Appreciate any help/advice.

67gtocharlie · 02-05-2003, 08:10 AM

I need the specifications (part #?) for the two bolts that attach the A/C bracket (the cast one that bolts on the SIDE of the head, to the front two head bolts). It appears that the rear bolt is a stud and the front one is a bolt. I have 6X heads on a '69 400 engine in my 67 GTO.
Appreciate any help/advice.

'ol Pinion head · 02-05-2003, 03:33 PM

The stud above the center passenger exhaust port on a '66-67 era Pontiac V8 with factory a/c, is unique in that it has a distictive thick hex shaped spacer design. Don't have one in front of me right now, but crude guess is the bolt head is nearly 7/8" thick. Stud will measure aprox 3.75" long from end of threads to where bolt head contacts the cylinder head.

In comparison, the D-port 1/2-13 head stud for the negative battery cable attachment measures 3 3/4" long with a .315 thick bolt head & battery cable stud area sticks out .700.

67gtocharlie · 02-06-2003, 06:09 AM

Anyone know if these are available, and if so, where? Thanks.

engineer · 02-06-2003, 02:24 PM

To the best of my knowledge, those bolts are unique, no other head bolts are that long. The original do have a unique head, 7/8 size, and bolt is 4.25 inches long. However, I don't know why you can not substitute a regular grade 8 bolt with a normal head. I understand that the unique head was necessary to keep the head from moving as the head bolt hole opening is greater than the bolt shaft diameter. But with the AC bracket in place, this new longer bolt does not require the special head because the AC bracket does not have an oversize opening like the head and the original bolt head shoulder with the bracket in place does not extend into the head. So the bracket itself is acting as a washer/spacer to take up the difference to hold the head properly torqued. Also, the need for the stud on one bolt is not being used for any application, so why both having it there? Just go get some good bolts from the auto store and be done with it.

67gtocharlie · 02-10-2003, 06:09 AM

Thanks for the replies, fellas. If anyone else has another opinion or suggestion, please let me know. Appreciate the help.

engineer · 02-10-2003, 09:55 AM

rechecked the bolt length is exactly 4.5 inches, not 4.25 as I earlier mentioned with 1/2 coarse thread. Sorry about that

Autotech · 02-11-2003, 10:33 AM

Ran into the same situation with a basket case '68. Engine had been assembled with Grade 8 bolts because it was pieced together from a collection of parts. '71-455 block, '78-6x heads. AC mount bracket #9789228. Completely disassembled to fix internal problems. Got rid of Gr. 8 bolts and got main stud kit and head bolt kit from ARP. Standard head bolts are one grade better than 8. ARP cannot provide the long bolts for the AC bracket. Measured thickness of head and bracket together at 3-7/8 in. Standard practice for bolt depth into a part is 1.5 times bolt diameter. These are 1/2 in. bolts so you need 3/4in. of threads to screw into block. A little more is good. 3-7/8+3/4=4-5/8in. Parts book lists #518031 head bolt at this length. Local dealer said not available and locater couldn't find any. Caterpillar is the best bolt store I have found for general purpose hardware of very high quality at a reasonable price. Cat lists a high strength bolt same grade as head bolts,#6F5282, 5-1/4 in. length with a 4in. grip length(no threads). Head bolts only have 2 or 3 exposed threads above the block so I use the bolt with longest grip length possible and cut off the excess. Am also using a hard washer #5P8245 which is 1/8 in. thick on these bolts. Be sure to check how much thread depth is available in the block by screwing a bolt in by hand to the bottom of the hole and marking it with black tape for an accurate measure of threaded hole depth so you can use most of the available threads and not bottom the bolts in the hole. With the bracket I have the two bolts are the same length. Get a Safe Source book at the Cat dealer to have a catalog of the available bolts. With the 6x heads you can bolt on the later AC bracket which does not use head bolts. The bolt holes are in the side of the head and use 3/8 bolts. I don't know if the rest of the compressor mountings work with the later bracket so I am not going to try that. Hope this helps,RWWAllace

Half-Inch Stud · 02-11-2003, 12:11 PM

I got a bunch of these factory bolts.

email me with the exact length you want.

"tbdET/1xxMPH/1.xx 60foot/28"/3.54:1/10"/469 #48/Flat HYD/DualQ-Jets/Offyl/3xx0Lbs
11.00/123MPH/1.50 60foot/29.5"/4.10:1/10"/469 #48/FlatHYD/DualQuad/Wenzler/3250Lbs
12.00/112MPH/1.61 60foot/26"/3.31:1/10"/469 #48/FlatHYD/Q-Jet/Torker/3650Lbs
12.70/103MPH/1.71 60foot/28"/4.10:1/12"/469 #48/FlatHYD/Q-Jet/Torker/3950Lbs"

67gtocharlie · 02-14-2003, 06:35 AM

I noticed that my 6X heads have a place to bolt on a bracket on the side of the head instead of using the head bolts. Does anyone know if the 6X bracket will work for a 67 compressor and are the other brackets still going to work? Anyone have the AC bracket that bolts on the side of the 6X heads?
Thanks for the help. couldn't do it without you guys.

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