Standard vs ported headers
 

Anyone have any proof of standard headers vs ported standard headers, I've seen a lot of yes it does make a difference but actual proof like dyno graph or whatever as friend who did very well on a motorsports degree has said it won't make any difference especially where intake side won't be touched

Give as performance a call they sell them and would be able to advise you also doing a search on here there is plenty of info they should improve spool and also torque throughout the rev range but a map tweek would be needed to get the best improvements match with a harvey smith up pipe

I had a Harvey up pipe ported and wrapped and made a noticeable improvement even before it was re mapped. Hope that helps.
Believe the hotter the gas stays the better it flows, it I'd did add to spool by about 300-400 rpm. On a td series 18g

Its fairly simple flow dynamics. Match the diameters to remove any lips at the mating faces and smooth out the roughness of the castings. Smoothing the surface finish reduces friction losses which slow down exhaust gas velocity from the head. Faster gas velocity, faster spool. If it was of negligible importance, why is it done on motorsports engines? Why are there companies making a living from porting and polishing heads? Even with an untouched intake, this will make a difference. The exhaust drives the cold side impeller to draw in air.

Yes exactly that my friend. Couldn't of put it better!

I know AS Performance have little to prove as their work combined with Harvey Smith is long established and documented and whilst the porting of headers was first it was soon followed by the introduction of what is now known as the Harvey Smith 'trick' up-pipe to add extra benefits

talk to some established mappers / tuners to get 'real world' results and differences - the likes of Andy Forest & Engine Tuner in particular have either assisted in initial testing or been very impressed with the gains over the years

Be aware that because of the (often) substantial differences in exhaust flow it requires mapping to add extra fuel to cope with the increased spool / power

As per my reply on type ra. After a few mods my car wasn't didn't want to pull over 377bhp. It had standard sti headers and the down pipe exhaust with a 2.5" join.
I took a die grinder to the headers and opened them up using a gasket as a template. I put a long champher and smoothed out the seams inside of the casting. I also fitted a proper 3" down pipe and 3" exhaust. It made another 37 bhp.
If you're gonna put more in you have make space to get it more out.

It's quite interesting to take the bits apart and see how badly matched the OEM pipes actually are.. I have also smoothed out the transitions between the heads, headers, cross 9oer pipe etc.

Not run the engine yet on my "ported" headers, but I don't think I've made it worse in any case.

I'll be running probably with an OEM up-pipe with the cat replaced by a bit of straight tube, but will consider a Harvey up-pipe as well if it doesn't spool as well as I've hoped.

If I was "normal", I'd go straight to Harvey up-pipe from AS, but I'm messing around with v-band connections for the turbo at present...

I've run cars with standard up pipe and headers, tubular headers and Harvey up pipe, and HKS tubular headers with their up pipe.
Experience for me, and on friend's cars is that the tubular headers and Harvey up pipe will give you slightly earlier spool at the trade off of slightly less torque, whereas the 3 bolt pipe that comes with the headers make it a tiny amount lazier but make more torque (10-20 ft/lbs).
A friend with an 18g billet got great torque out of the GT Spec headers 3 bolt up pipe.

With the HKS headers on my standard vf30 my JDM bug STI made 353/350 at SRR, which is a better bhp and torque figure than I managed to previously make on a UK widetrack or bug WRX with a vf35 and standard headers with Harvey pipe.
It's all horses for courses - each car responds differently depending on so many factors like supporting mods, engine condition, turbo condition etc etc.