MICO Master Cylinder Attachment Fasteners

[OldGuy]

Guys, I need some confirmation regarding the 3 bolts that attach the master cylinder to the firewall adapter.

Were these bolts 3/8-16 x 1.00" long hex-head (9/16") "garden variety" plated hardware store (from yester-year) units that had no head markings? Or were they...................?

Any help would be appreciated.

Thanks in advance for your help.

Frank

[gt350hr]

   Frank,
       The bolts used on 6S477 ( one of the earliest to have a Mico) were  , two non plated, 9/16ths wrench size . 3/8ths coarse by 1" long on the upper two holes and a ''header bolt" 7/8ths thread length , on the bottom hole.  It is important to note my car along with MANY others had the mounting bracket changed "under warranty" to an "improved design" @ High Performance Motors.  Sooooo, the question "could be" did a mechanic @HP use a header bolt on purpose or was it done at SAI?  I have seen it on several other cars so I know it wasn't a fluke. The header bolt is the same style as the header bolts supplied by Cyclone ( not Rockwell) at the time. Those masters were installed at SAI so some bolts had to be added by SAI over those assembly line furnished bolts.  I would like to hear what other "un molested" cars have. I say unmolested as the header bolt could easily be mistaken as "previous owner/mechanic added".
     Randy

[Bob Gaines]

   Frank,
       The bolts used on 6S477 ( one of the earliest to have a Mico) were  , two non plated, 9/16ths wrench size . 3/8ths coarse by 1" long on the upper two holes and a ''header bolt" 7/8ths thread length , on the bottom hole.  It is important to note my car along with MANY others had the mounting bracket changed "under warranty" to an "improved design" @ High Performance Motors.  Sooooo, the question "could be" did a mechanic @HP use a header bolt on purpose or was it done at SAI?  I have seen it on several other cars so I know it wasn't a fluke. The header bolt is the same style as the header bolts supplied by Cyclone ( not Rockwell) at the time. Those masters were installed at SAI so some bolts had to be added by SAI over those assembly line furnished bolts.  I would like to hear what other "un molested" cars have. I say unmolested as the header bolt could easily be mistaken as "previous owner/mechanic added".
     Randy

I have also seen the header bolt a number of times.

[Rocket]

I've owned 6S550 since the fall of 1967, and the bottom 2 bolts are header bolts. That's the way it was when I bought it, and service records from Howard do not show that the Mico bracket was changed. Ron

[OldGuy]

   Frank,
       The bolts used on 6S477 ( one of the earliest to have a Mico) were  , two non plated, 9/16ths wrench size . 3/8ths coarse by 1" long on the upper two holes and a ''header bolt" 7/8ths thread length , on the bottom hole.  It is important to note my car along with MANY others had the mounting bracket changed "under warranty" to an "improved design" @ High Performance Motors.  Sooooo, the question "could be" did a mechanic @HP use a header bolt on purpose or was it done at SAI?  I have seen it on several other cars so I know it wasn't a fluke. The header bolt is the same style as the header bolts supplied by Cyclone ( not Rockwell) at the time. Those masters were installed at SAI so some bolts had to be added by SAI over those assembly line furnished bolts.  I would like to hear what other "un molested" cars have. I say unmolested as the header bolt could easily be mistaken as "previous owner/mechanic added".
     Randy

I have also seen the header bolt a number of times.

GREAT feedback, guys! My followup question would be: Was the bottom MC mounting bolt on cars with a later serial number (my serial is 6S803) a header bolt? If so, was it a Cyclone style or maybe a Rockford style (the bolts used on my headers are Rockford)?

As always, thanks for your responses. This forum is extremely helpful.

Frank

[acman63]

Ive had two of these cars in here the last year and both had these bolts and nuts on them.  I believe I was the first one to take the cars apart

[gt350hr]

  The important thing to remember is this conversion was done at SAI or HP Motors ( early bracket change out) , not the ''closed environment" of the San Jose assembly plant by people who "just did the job" rather than follow a "procedure"  like line workers had to do.
      "Some" variation should be expected.
        Randy

[Rocket]

Will have to look, but think the bottom one is not a header bolt. Ron

[OldGuy]

Ive had two of these cars in here the last year and both had these bolts and nuts on them.  I believe I was the first one to take the cars apart

Jim, was the bolt with the recessed face and captured lock washer the bottom bolt?

Thanks. I appreciate the feedback/pictures.

Frank