[John]

An old time local Model A motor re-builder near me used to braze the tube into the rear main cap in the many motors he overhauled. I asked him how he did it without melting the babbitt and he stated that he submerged most of the cap upside down in a pan of water and had great success that way. A very simple solution that worked for him. The same solution could be used when spot welding the tube in place.