Frame head cracks, just to be clear.

[Richard48Y]

If I have read post correctly and just to be clear, S1 frames do not crack at the frame head but S2 do.
On S3/TC Lotus reversed the direction of the end flange and they do not crack.

But of course they all rust.

[jbcollier]

S1 one chassis don't crack because they rust out first...

[gideon]

I believe the change they made for TC frames, to address the cracking issue, was to weld the bottom part of the head to the backbone.  The direction of the flanges on the sides of the backbone was reversed for the Esprit S1 frame.

The anatomic metaphors make it sound as though the frame is a vertebrate skeleton.  So, the bit at the front is the 'head' and the bit in the middle is the 'backbone' or 'spine'.  Presumably, then, the two bits either side of the engine are the 'legs' (or fins, but that would be ridiculous).   I'm just not quite sure what to call the bit connecting the two legs at the back...

Edit - I checked a couple of photos and I was wrong the flanges.  They were reversed for the TC frame.