1986.5's engine is knocking is it junk?

ok here it is i have a 1986.5 NA 5 speed and i was on the hiway the other night toying with an older nissan maxima, i got bored and decided to see what the thing could do i got it up to 148 and with in about 4 seconds of being there the car started to get a little slugish and slowed down to 130 even though my foot was pined to the floor when i pulled off the hiway i noticed a knocking coming from the engine at around 1800-2400rpm's any higher or lower and the noise goes away i think i messed up a rod or something and i haven't driven it since i got it home
i just want to know if the engine is messed or what because this car is my babby and i would hate to have to get rid of it