I removed the 400bb from my 72 charger that I just started restoring. Found both rear lugs where the motor mounts bolt to the block broken off of the block on both sides (see pic). Will a machine shop be able to weld something on that will work?
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Though there's no accounting for casting
integraty, a straight thru bolt has a
tendency to transfer the load thru both
holes but that load is multiplied. When we
designed the placement of a 440 in a tube
frame, we ran those loads on a stress
analysis program. The stress is reduced
by half if there are two separate bolts.
I believe your block can be fixed if you can
find a shop that has an experienced cast
iron welder. Might be pricey. Compare
replace vs repair. My top rear tab was
gone, as yours. So far it's holding up.
Zoom in on the rear top mount and
you'll notice a slight stagger where the
tab was welded. It's imperative that you
install a bolt (grade 8) with a clearance
that is pretty tight. You want the mounts'
rubber taking the load, not the bolt.