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MG TD TF 1500 - Carriage Bolt Size - TF Firewall

I caught this just in the nick of time for my TF restoration.

> On a TF, what is the diameter of the carriage bolts that attach the top of the firewall to the tub, and through the wedges at the hoop at the corner of the firewall? The square shoulder of 5/16" carriage bolts is a tight fit in the firewall holes ... which will lock them in place. I can maybe see evidence of the square shoulders in the holes(?)

> What is the diameter of hex head bolts that hold the sides of the firewall to the tub and to the front of the body frame?

Here's why I ask:
My TF had 1/4" diam carriage bolts along the top of the firewall and 1/4 hex head bolts along the sides of the firewall when I disassembled it. The only 5/16" carriage bolts (4) were at the two wedges at the hoop. I assumed that the 1/4" bolts were correct. I hadn't considered using 5/16" carriage bolts until Bruce Cunha posted his update to his TD fastener list.

Thanks for your help,

Lonnie
TF7211

(photo TF9052)


LM Cook

On TFs,as stated before, 1/4" BSF bolts except the four 5/16" bolts,wedge to chassis hoop.

Of course,these 'wedge' bolts are by necessity different lengths.

Cheers
Rob Grantham
Rob Grantham

Ok, so we are all on the same page, are we talking BSF or Whitworth.

I rechecked and the kit of firewall bolts I received has 5/16 BSF (1/4 W) heads. So when ordering, you would use 5/16 BSF.

I get confused on this as one set of box end wrenches I use just has a size number and I have to remember they are whitworth.

My open end wrenches are marked in both.
Bruce Cunha

Rob and I are talking about the diameter of the bolts.

Here’s a good explanation of BSW and BSF wrench markings -
http://progress-is-fine.blogspot.com/2017/01/the-evolution-of-standard-wrench-sizes.html

Lonnie
TF7211
LM Cook

Spot on Lonnie C.

Cheers
Rob Grantham
Rob Grantham

If that is correct, there is a difference between the TD and the TF, which I would find odd. I just measured the firewall bolt and it is 0.312 below the head, or 5/8. All the same size all around the firewall.
Bruce Cunha

Is that 5/16 or 5/8”?

Peter
P G Gilvarry

Bruce,

I don’t know enough about TDs to comment. I found a couple of threads in the archives that confirm Rob’s statement about bolts for TF firewalls.

Lonnie
TF7211
LM Cook

5/16 peter, I type bad.
Bruce Cunha

This thread was discussed between 02/12/2021 and 05/12/2021

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