Sifus,

i'm planning to undertake a PnP job to my 4G15 head whereby upon reading some articles about it, it is claimed the port entry & exit is already achieving 95% flow efficiency while at the port bowl is around 75% and only 50% at the port throat & valve seat...

http://www.popularhotrodding.com/enginemas...eads/index.html

hence, should we just ignore polishing work to the exhaust port and ask the machine shop to just concentrate on reprofiling the port bowl and undertake a multi-angle valve cut plus chamber deshrouding?

moreover, some machine shop is able to increase compression ratio of the head by welding some metal filling onto it....should i also go for it?

http://protoncars.biz/index.php/topic,25613.40.html

members feedback are highly appreciated..






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a good suggestion...but as my project is actually trying to improve the 4G15 FC to a 20 km/l (yeah i know it is unbelievable but i'm an ardent fan of Obama's slogan - Yes, WE CAN), i need to read-up and gather good technical info's on how to achieve this and one way i think is to improve the engine volumetric efficiency...