Phildodd06

Is it worth doing?

I may be having 2 remove my heads to do my valve guids & seats, thought while it was out id have my heads ported & polished.

Is it worth while?
Has anybody had it done, could you feel any diffrence?

How much was it?

300bhp/ton

Port but not polish. I heard a wise man once say if someone offers to polish you cylinder heads - run a mile.

STiFreak

iTrader: (4)

I have posed this question to some of the experts before and the general consensus seems to be that the standard heads are pretty good and it is not worth the cost unless you plan to go all out for power (i.e 500bhp and above).
I am not sure if it is the same for different model years, or if there is a major difference between WRX / STi, but I am sure will be able to answer.

GazTheHat

I had mine done and it included a custom up-pipe. £400. All wrapped too.

Couldn't tell you if it made a difference, as other mods were done at the same time.

300bhp/ton

do you mean cylinder heads or exhaust manifold, aka header?

GazTheHat

Ah bollocks, yes, wrong thing.

gpssti4

iTrader: (6)

Porting, yes; as it improves flow.
Polishing, no; as a slightly rough surface promotes better mixing of the fuel and air.

joekont

The thing to do is port and polish to the injectors then port only with a motled finish after. If you polish once fuel is in the air, it will make the fuel condense out on the polished surface.

Phildodd06

Basically, when i send them off, just ask for them to be ported, but NOT polished

Does anybody know if its a noticable mod?

Im just in the middle of porting my headers and heat wraping them.

harvey

iTrader: (48)

Porting heads is quite a long way down on the priority list and unless you have access to a flow bench you will never know if what you have done is correct. If someone else is doing the porting and charging you then it is not a very cost effective mod and only needed where every last bhp counts. When porting generally, not just head ports, sometimes the results are not as expected as it is not just a simple mater of widening a particular port to a maximum diameter etc.
If you are doing it yourself, restrict your activity to a general tidy up and knife edging, otherwise give it to someone with a flow bench that has learned from their mistakes as to what is actually required.

Klaatu

When refering to porting and polishing heads, polishing doesn't mean "shiny" ports. You are right, shiny and smooth surfaces do not help (Wonder why VW put plastic in their induction system), but a "polished" head/ports DO help if is properly done. The "polishing" after porting is done and usually means removing burrs and smiliar along gasket seals etc.

Gas flowing it could help, but it's lots of money spent for little gain unless you are into serious engine, induction and exhaust work.

Then again, you could "blue print" it if you wanted to go OTT!

Phildodd06

Not really a worth while mob thn, dont think ill bother with it.

172sport

iTrader: (6)

CNCHEADS - Subaru Impreza

Phildodd06

Deffo not worth it for that price, a remap would be cheaper