The turbo 4G63T engines also prefer the smaller ports, rather than the much larger ports found on the likes of the NA RVR engines.
But remember, production engines are ALWAYS a compromise. When you're chasing the numbers, then you have to make sacrifices.
But given that porting aside, you're still going to have to do the same freshening up work to any head regardless of it's configuration, you might as well start with the better one. Then you can use the money you didn't spend on porting the inferior head, to give it a tickle up.

Its all about the G spot, too large just destroys it :))

Il share the knolage and experience i have to date,
From the conversations iv been recently having with Keith Davison who is a well respected race engine builder in Victoria.....the engine (ca) I'm getting done at the moment, he is going to clean up the ports (casting marks and bumps) and has mentioned there is a lot of room for improvement around the spark plug area and in the combustion chamber area.
Il be getting the manifolds match ported and a casting marks cleaned up then up the boost for more hp :)))
For someone who knows there trade it's quite apparent where is restrictive and what will (has) work. The more money (with the right contacts) you have to reach the hp goal you must start with.

Taking all these things into account hp/boost/kw and the budget
Will be the starting point. If anyone who is serious about getting a motor built (not just talk about it) and would like Keith's number then hit me up! It's all about who you know

Only fair to put up the one person I know will make a very successful CA18det and that is Steve Newing of speed technology. He has made more than 240hp in NA trim reliably which is no mean feat. Yatala headworx have made the most hp reliably on the drag strip there are a few others eg. Lewis engines etc

Hi guys been doing some reading about porting,is it true to say that opening a port to much(ie converting an 8 port into 4 larger ports)can actually have problems with flow charactoristics than the standard euro 4 port.Like i was once told that i big muffler on a small powered car can cause back flow because the engine doesnt have the power to push the fumes out all the way.If the inlet manifold is matched to the port size and the injectors are in the middle off the new port will there be any problems with getting the fuel down the chamber.Is it also fair to say that the bigger port will benifit with higher boost.

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The other big upside of the factory four port head is the head of the valve stays clean. I've seen lots of eight port ports where the secondary ports valve is badly encrusted with stuff that would have been washed clean had it been exposed to the fuel spray from the injector.

what cams/turbo will you be using?

Hi fellas prob a gt2871 or gt30 dont know about the cams leave it up to dave from awsome auto.Im not doing any off this myself but are keen to learn.