mejo major yang pagpalit ng valve seals kasi inaalis usually yung cylinder head to access the valves and seals.

pwede din sikwatin na lang yung valve seals without removing the head although mas complikado at not sure kung meron gumgawa niyan dito sa atin.

pag inalis yung cylinder head always inspect yung internal parts like the engine block, sleeve, valve guides, and the valves itself. replace all oil seals with new ones. also replace gaskets.

pwede mo na din isabay yung timing belt at tension bearing especially kung mejo matagal na ito or nearing replacement.

one thing i've learned kung papabuksan mo ang makina is to be ready with unexpected costs. usually merong unexpected sira inside the engine.

as always, go to ur trusted mechanic.