i installed a rebuilt master cylinder in the bottom of the reservior theres a philips head screw on the larger fluid part the rebuilt unit did not have the screw but the threads to screw a screw in were there the old 1 had the screw is it important what is it do i need the screw or not?

 

Most likely you do not need it. During the rebuild they may have fixed or deleted the reason for the screw.

If for peace of mind and you can remove it you might put it in the new one.

 

tried the old screw only would screw half way no leaks in the`cylinder brakes work fine so ditch the screw i guess now i need to install a water pump looks really easy compared to previous cars ive owned im very happy with it i wish it had the slant 6 with the manual trans its a 360 w/3 speed auto has some ***** for a 77