I took the exhaust manifold off my '93 wrx yesterday to port!

straight away I could see the black soot line that people say needs to be removed, I layed the gasket over the top and thought......wow how restricted is this exhaust!

But then also noticed the soot line on the engine also!!!

So exhaust ports and manifold are actually the same size! the soot line is from the thin spacing of the gasket!
So how much difference does it actually make porting the headers (has anyone done any tests?).

All I can see is that the standard headers will have slight...slight turbulance!

comments plz

 

i can only give you a subjective reply; post fitting Harvey Smiths ported headers and slipjoint up pipe the delivery seemed smoother and much more refined. The car is now nicer to drive

it needs a remap too because i'm now hitting fuel cut, so i must be producing more boost...I'd say they are worthwhile mods

 

Yes its worth it, Harvey did mine and we timed the car on the bypass near pauls (his mechanic) on a run between a couple of lampposts before and after fitment, the difference was noticeable!

Ive since fitted GT Spec tubular headers and can say that this mod is dramatically apparent! The ported ones managed to get me 367HP / 347Lbs of Torque though with one of andys 20g's so pretty good overall if youre on a budget!

 

m8,how much more did the tubular headers give you over the ported one's?....just trying to work out if it would be worth my while shelling out the extra for the aftermarket headers for my my05 sti

 

anymore???

any gas flow experts want to shed some light

 

Ive not had the car on the rollers since i fitted the GT Spec Tubular headers and ive since fitted a bigger Intercooler and Injectors with hopes of being closer to the 400HP mark so i couldnt say how much difference gain there is over the OEM ported ones. What i can say though is that the car pulled a lot more in midrange and the mod was instantly noticeable. If youve got the money and are looking for future modding capacity then get the tubular ones but the ported were fine for 367HP / 347Lbs so that should give you some idea of their limits!

 

cheers guys!

I've now ported where the manifold meets the heads!

but got me thinking, the manifold is bolted together into 3 sections (haven't split as yet - cos don't want to buy new gaskets if not necessary)

but if the gasket in these sections is larger than the bore then surely I'm going to have to port these also???

it's just that I've never heard any referance to this

????????

 

you will need to port all the sections which will mean taking it apart, you won't need to get new gaskets as the old ones are usually ok.

 

cheers scoobysmiff!

 

will porting the cross section cause - what they call 'balloning' to the airflow?

 

afternoon all!

 

this may help:

ported/polished/wrapped oem manifolds webpage - NASIOC