Just about have my motor swap completely finished, I put a 7.3 from an 89 into my 73 highboy. I am now on brakes and after bleeding them and putting new calipers on the front the brakes felt normal, so I plugged the vacuum line on the booster and no longer have any pedal travel, and the brakes don't work cause I cant push the pedal. I can unhook the vacuum line and apply brakes with a lot of effort and it takes time to stop, nothing I cant drive with but I really don't want someone to pull out in front of me and get run over by this monster. Do I need a new booster for the 73 body+pedal length or new booster from an 89 to match the pull of vacuum from the motor? or is there something simple I can do now with the parts I have?

 

the Vacuum pump should make plenty of vacuum for the 73 booster... I would test to see if you actually have vacuum or maybe a leak somewhere.

 

Has plenty of vacuum can feel when I put my thumb over it feels like a vacuum cleaner

 

did you change the Master Cylinder or anything related to the booster such are rod length or the check valve. IF not then you should just do the standard Booster tests.

https://www.knowyourparts.com/techni...r-diagnostics/

 

The master cylinder was changed before I bought the truck, I received it with no motor and it wasn't running so I do not know if the brakes were functional before I swapped motors. What can I do for rod length or how can I check

 

they make a tool for checking rod length......



The tool is easy enough to make....
here it is in use.....



most fords are 24-25mm length on the booster.. you could always use a dab of grease on the rod and test fit the MC unril you just make contact.