i need some advice from you fellow tsikoteers.

my car is experiencing pre-ignition lately and i had it checked sa 3 different motor shops last saturday. they all advised me to have my engine a top overhaul na. the pre-ignition is caused daw by too much carbon build-up on the engine's valves. maski nasa tamang timing ang engine kasi, umaandar pa rin sandali ang engine maski patay na sa susi ang car ko.

i've read here before yung carbon clean for engines, hindi ko na nga lang makita dito sa workshop forum. magkano kaya yung carbon clean na yon? better alternative ba ito sa top overhaul??

top overhaul will costs me daw P2,500-P3000 (labor) plus those valve seals and gaskets. sa casa nag-inquire rin ako, P30,000 daw! sa westwin, Pioneer Center P38,000, mas mahal pa sila sa casa! kapag top overhaul ba, may pa-machine shop pa ba?

pls. help me naman, paki-post sana maski phone number ng carbon clean shop or your trusted motor shop sana.
thank you.