Firewall bracket bolt size 1911-1912
What is correct for 1912 firewall bracket bolts? The guidelines say 5/16 coarse thread. The head size is 13/16 and a ½ inch nut. This is the photo shown.
I have 3 original firewalls for my three 1912 cars. The early , February car , has a bolt head imprint on the firewall which shows it to be a one inch head. The other two later firewalls for the later cars, show head imprints to be 13/16.
So my questions are, what is the correct head size for 1912 and what is the length of the bolt and are there washers?
The bolt in your picture is the correct one.
The correct nuts use 9/16" wrench size. There should be a flat washer just barely larger diameter than the nut.
anyone know the head diameter and bolt length?
Head diameter is 1". The bolt length is 1 3/4".
I believe these are called "Step Bolts" and are available from good hardware supply houses--Orchard Hardware Supply USED to carry them! Collier's Hardware in Chico still had some last I looked (But that doesn't help those of you who do not live near Chico, CA! BTW, they had all the rivets I needed when I was fixing my T frame.). The nuts are a different situation, washers are PROBABLY SAE size, not USS which seems to be so prevalent nowadays.
So I am assuming that the Guidelines are incorrect and that Royce is correct?
The guidelines say "5/16 coarse thread. The head size is 13/16 and a ½ inch nut"
The head in the photo sure looks like its an inch….