hello everyone!

I recently bought a 99 ek with a d16y7, car is practically brand new, it came from a performance shop, they rebuild the entire car with new suspension, engine rebuilt, ect, 0 rust yada yada, they reused alot of the old parts like the starter, battery, ect. i drove the car home no problem. but the car sat for 2 months, and i knew the battery was bad in it because the guy told me, so when i decided it was time to start her up again, i went straight to the auto store and bought a battery that currently reads 12.79 as of right now. my car didnt want to start, all id get was a click, i figured its time for a new starter, i replaced the starter, and same thing, but this time the new starter engages but makes a clattering sound, so i disconnected it from the bell housing, and jumped it with the key on from the solenoid, and i can physically see, when i touch the battery, it engages out, but then chatters, the old started just engages but nothing happens, i have no idea what is going on. when i read battery voltage when starter engages, i go from 12.79 to 11.70 under load. i have no idea what to do after this... all the grounds are brand new, no corrosion ect. im about to put the new solenoid onto the old starter just to see but im like losing my mind, if anyone has any tips or things i can do, please help me! much appreciated. if im correct, a full voltage of power drop sounds bad no?

 

Charge the battery on a battery charger, then check all the grounds and make sure they are tight. Especially the body to trans ground