Ok, I've said to someone on the Club Triumph Forumthat I would show them how I changed the battery box on the Spitfire. So I thought, why not write a blog post and then it's easily available for future reference.
I did this job in early August 2006, part of the over optomistic mad rush to get the car finished for a trip around England and Ireland in September.....
Anyway, here's what I did. I started by drilling completely through the spot welds from the top, even though it's a small panel there's loads of them!
I tend to use around an 8mm drill bit, you can get away with smaller but I find plug welding afterwards easier with a bit more space.
You could also use a spot weld cutter, I have one of these an find it really difficult to control. The advantage here would be that you could avoid welding from underneath if you didn't drill through the body.
Once I drilled all the welds, I bent back the two stiffening brackets and lifted out the box.
That's where the photo's end unfortunately, but after that it's clean all the paint off the flange on the new battery box where you're going to weld. Put it in place. Bend the stiifeners back. Plug weld through the holes you've already drilled (from underneath all the way round and above for the stiffeners). And tidy up.
Biggest challenges are managing to squeeze the flanges tightly together (you can only get a clamp on at the front) and welding from underneath. On the 1500 access is really difficult under there. It's not easy to get in to grind any messy welds down either, on the other hand, no one will ever see them!
Havn't got a close up of the finished job, but you can see it here.
and here.
