Bolt ID
Race Director
Joined: Apr 2005
Posts: 11,277
Likes: 2,139
From: Bowling Green, Kentucky
OK, here's the real scoop. LOOK AT THE BOLT HEAD. If it came off of a GM car and has six radial GROOVES, it is most likely a "Place" bolt, a very specialized part, GM used only on those flywheel-type applications. The grooves are not an identifying "head mark", they are functional.
On the other hand, if it has six radial lines that are raised above the flat surface of the top of the head,, like the 67 caliper bolt, it is NOT a place bolt. It is Grade 8 machine bolt, the strongest variant normally used on GM cars of that period. The 1967 caliper bolts referred to above had six radial lines raised above the bolt head flat surface. They were not "Place" bolts, though, they were normal Grade 8 bolts.
It much more difficult to create dies to make a fastener head with grooves, so anytime you see it, it means someone went to lot of trouble, for a reason , not just to mark the bolt
On the other hand, if it has six radial lines that are raised above the flat surface of the top of the head,, like the 67 caliper bolt, it is NOT a place bolt. It is Grade 8 machine bolt, the strongest variant normally used on GM cars of that period. The 1967 caliper bolts referred to above had six radial lines raised above the bolt head flat surface. They were not "Place" bolts, though, they were normal Grade 8 bolts.
It much more difficult to create dies to make a fastener head with grooves, so anytime you see it, it means someone went to lot of trouble, for a reason , not just to mark the bolt
That being said, the bolts that held the two front caliper halves together on my 1967 disc brakes (not the caliper mounting bolts) had this same head configuration (i.e. place bolt type head). However, they were a different diameter and thread. Now the brakes had been SS sleeved by Vette Brakes and Products by the previous owner back in 1979..........so I cannot say for certain if VB&P or GM installed them..........but there was no denying the head design.
Larry
Melting Slicks
Joined: Sep 2009
Posts: 3,382
Likes: 1,258
From: MI
2023 C2 of the Year Finalist - Unmodified
2022 C2 of the Year Finalist - Unmodified
2017 C2 of Year Finalist
I won't argue with you. I used the term "headmark" to call attention to the special design/configuration of the head on the bolt. This was my mistake, as I should have used a better or more appropriate word.
That being said, the bolts that held the two front caliper halves together on my 1967 disc brakes (not the caliper mounting bolts) had this same head configuration (i.e. place bolt type head). However, they were a different diameter and thread. Now the brakes had been SS sleeved by Vette Brakes and Products by the previous owner back in 1979..........so I cannot say for certain if VB&P or GM installed them..........but there was no denying the head design.
Larry
That being said, the bolts that held the two front caliper halves together on my 1967 disc brakes (not the caliper mounting bolts) had this same head configuration (i.e. place bolt type head). However, they were a different diameter and thread. Now the brakes had been SS sleeved by Vette Brakes and Products by the previous owner back in 1979..........so I cannot say for certain if VB&P or GM installed them..........but there was no denying the head design.
Larry
Mike
Team Owner
Joined: Oct 2000
Posts: 38,897
Likes: 1,926
From: Washington Michigan
OK, here's the real scoop. LOOK AT THE BOLT HEAD. If it came off of a GM car and has six radial GROOVES, it is most likely a "Place" bolt, a very specialized part, GM used only on those flywheel-type applications. The grooves are not an identifying "head mark", they are functional.
That's a PLACE bolt, commonly used on Corvette disc brake calipers and flywheel bolts. The indentations on the top of the bolt head work in conjunction with the machined undercut on the bottom of the head to resist loosening when the bolt is torqued.
Mike (Vettrocious) has forgotten more about bolts and threads than any of us will ever know or learn
Melting Slicks
Joined: Sep 2009
Posts: 3,382
Likes: 1,258
From: MI
2023 C2 of the Year Finalist - Unmodified
2022 C2 of the Year Finalist - Unmodified
2017 C2 of Year Finalist
DING-DING-DING, we have a winner!
That's a PLACE bolt, commonly used on Corvette disc brake calipers and flywheel bolts. The indentations on the top of the bolt head work in conjunction with the machined undercut on the bottom of the head to resist loosening when the bolt is torqued.
Mike (Vettrocious) has forgotten more about bolts and threads than any of us will ever know or learn
That's a PLACE bolt, commonly used on Corvette disc brake calipers and flywheel bolts. The indentations on the top of the bolt head work in conjunction with the machined undercut on the bottom of the head to resist loosening when the bolt is torqued.
Mike (Vettrocious) has forgotten more about bolts and threads than any of us will ever know or learn
Thanks John. And I forget more every day
Interestingly, the 67 calipers now on my just finished 63 don't have place bolts. Whoever re-built the calipers must have switched out the place bolts for similar grade 8 bolts, just like what I said not to do...
Time to ask Richard Fortier to dig into his stash of old bolts...
