Working on a 70 442 M/T. Found a very large crack on the engine crossmember. Anyone ever seen a crack like this before? Found a smaller one today around the hole where the fuel & return lines go through the frame. This car has probably been drag raced in it's past - worried there is a lot more damage that what I can see. Thoughts?

 

That makes no sense. The crack is on the passenger side, which is in compression from engine torque. That's why it's the driver's side motor mount that always fails - that side is in tension. Was this car drag raced in reverse?

Seriously, could be due to the vibration of solid motor mounts, perhaps? In any case, the frame is mild steel. Grind a vee groove along the crack, drill crack stop holes at the ends, and get a good weld penetration.

 

Would check that frame for square, use a pro to correct those cracks, like Joe said your only got one shot to get good weld penetration.