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TR2/3/3A Floorpan to frame bolt size

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R

RC64

Jedi Hopeful
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After the body work and painting was completed on my TR-3A, when the body was set back on the frame 5/16" x 24 bolts were used to secure the body to the frame at the various connection points. I am now in the process of installing the hardware for the seat belts. I purchased four 5/16 x 24 eye bolts from McMasters with the intention of using two of them to replace two of the mounting bolts (check the photo below) in the aft outboard holes behind the seats. When installing one of the eye bolts I noticed that the bolt seemed to be a little too loose in the nut even though when cinched down it did appear to be tight. I experimented with a couple of the other bolt holes and am now wondering if I'm using the right size.

I checked the parts catalog but couldn't find any reference to the spec for these bolts. I'm wondering if they could be metric. Perhaps M8 (13mm) which is just a tad larger. I'm going to see if I can find a M8 bolt locally to try it. Does anyone know specifically what the size should be for those bolts?


DSC02003a.jpgDSC02001a.jpg

The loose eye bolt was what came off the old floor pan when the restoration was started. It was obviously an add on before I bought the car used in 1963.

Any other guidance on good ideas for mounting the hardware would certainly be welcome.

Rick...
 
Definitely 5/16 UNF originally; but who knows what sins have been committed since then?

SPC lists them as HU0810/P, which the magic decoder ring confirms is 5/16NF x 1"
 
I pulled out a new body mount kit to check for you. They are not metric...and there are both 5/16 AND 3/8" fine threads in the kit. Sorry, I don't remember which bolt fits in which mount.
 
John...

It would have to be the 5/16 in this location. I'll go with the 5/16 eye bolts I have and forget about checking the metric.

Rick...
 
RC64 said:
I'll go with the 5/16 eye bolts I have and forget about checking the metric.
Click to expand...
If they are noticeably loose, that means the threads are damaged (probably rusted oversize). You might want to think about repairing them now instead of waiting until after the eye bolts pull out.
 
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