Installing new guitar neck??? :)

so ive just bought a 24 fret "jackson-style" guitar neck to replace a 21 fret "strat-style" neck on a cheap guitar... the new neck is brand new and i use gauge 10 or 11 strings on my axe... does anyone know if i will need to alter the truss rod when i install the new neck?? i would assume at least 1/4 turn as soon as i put the strings on but im not sure :P

btw no information provided with the neck, i asked the seller but he doesnt have a clue lol. any help much apppreciated!! :D

post this in the guitar section, you might get an answer