The following is what the 2 retaining bolts should look like
2 bolts were recently removed from Matilda the 1928 Chev during a working bee with Terry Petridis, and the other 2 bolts were taken from an 1928 engine picked up recently for spares.
Both sets of bolts are extremely corroded, and could have quit easily snapped in the process of removal. Compare them to a new bolt.
After seeing these plus a similar set of bolts on the Red Chev when I pulled the housing off during the pre wedding restoration 1997, only 24 years after a full restoration, the moral of the story is
"Check your bolts, as just because there are no leaks does not mean all is well"
These days I try and use stainless steel bolts or at least a plated bolt