We have a 1971 Torino. We installed disc brakes, it had a slight pull to the left. We took it to one of the big box auto stores for an alignment. They messed it up and now the steering is loose. We have checked all the suspension parts all seem tight. It drives straight until you hit a large bump then pulls hard to the right. Any ideas?

 

Does 1971 still have the linkage power steering? If it does they may have adjusted the valve to the edge of the travel and when you hit a bump may hit the edge of the valve and try to turn.If that is the case may have to take it to someone that understands the system and center the valve and steering and start over.
Mark

 

sounds like it has bump steer. Assuming this car has parallelogram steering linkage. if the center link is not level it will effect how the toe moves over bumps. Typically you see this after a front end collision but maybe things were moved during part replacement.

normally, when the suspension jounces, toe should move negative (outwards) equally for each tire. When the steering linkage in not level, as the suspension jounces (moves up) one tire will toe out and the other tire will toe in. This creates a directional change.

The only way to see this is to either watch the toe change as the car is jounced and rebound (if the car is not jounced the alignment will appear normal) while on an alignment rack or measure the steering linkage from a fixed point on the car.

Take it to a good alignment shop that knows how to correct bump steer.