yep.. Cast iron is very brittle and welding it does not improve the strenght of the material around the weld.. The weld itself is strong, but without a serious heat treatment (normalising and annealing) it will always be a guess how safe your setup will be.

But nevertheless;

The welding looks neat and I can understand you were desperate, here in NL the rocco adapters are also hard to find..

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v40 d4 r-design 2014
Volvo 244 gl 1978
Volvo 780 Bertone 1987
Mini 1275 1977
Mini 1000 1987