gas flowing cylinder head

has anyone had their head gasflowed? maybe bigger valves ect
can they comment on the performance gains? rolling road figures before and after would be good

Hi mate, unfortunately thats a prity impossible question to answer as most if not all people who have their head ported, polished ect ect wil also have a re, map, fmic, bigger turbo ect ect added at the same time...

Having said that I can fully recommend getting it done even if you jst have that and a re map you wil have wayyy better throttle response, better low down power, not so much lag ect.

Hope this helps...c

it depends ,a simply headwork will raise power around 10%
if well done, it doesn't matter too much the flowbench numbers
in my experience, and experience is the key for good results

bang on what cheese said. its not about max power, its about the delivery.

who would want 10% only at the top rev range when you could get 5% from idle to max revs?

and, again, its about torque on road cars and tractability...

If you put ported head with bigger valves you will lose throttle response and power in lower range of rpm.

Emagine that you drink with a straw, a tiny straw will give your drink much sooner to your mouth but you will have to use a lot of effort to drink cc 0.5 liters in short time. And with fat straw you will have to suck more to get drink to your mouth but when it gets to your mouth you will drink 0.5 liters much faster than with tiny straw.

In my opinion GO, port your head. You will gain so much power in high rpm's that when you drive with cc 70% throttle you will feel that car is going like on WOT on stock head.

BUT, porting a head with a stock turbo is like buying a rose to a whore, because stock turbo is dead at 6500rpm.

Excuse my English, hope you understood me

I'm running 300bhp at the moment, after a little more but the turbo dynamics stage 2 turbo is maxed out according to flea.
Was just wondering if it would be a waste of time or not?
Appreciate people's opinions

if well done it's a good improvement
it depends how much you pay the work (500£-1000£ or more?)

well from personal experience you DO NOT loose low down grunt you IMPROVE it!
I understand what your trying to say with the whole straw thing but its simply not true when it comes to cars..

more fuel/air = more power... provided that fuel is being burned efficiently that is..

People in WTAC use 2.5" intake pipes @800+ bhp. (with anti lag)
People in drag series use 4" intake pipes @800+bhp (with LC)
Think twice why is that using like that
If you increase port diameter you loose air velocity.

I never done only head porting to compare, there was always some other mods. But I've spend too much money on my head with 3.5mm bigger valves to avoid later boost. The first thing that guy who is porting race heads and know my laggy car told me "this will be too laggy in compare to old head, don't do that" But, I have diesel car for daily driving so don't want low rpm range power in my weekend/track car

I once fitted a ported head and changed nothing else. Obviously a tad lean though the car was running a chip that's known to be generous with fuel. There was .5 bar less boost showing on the gauge after it was fitted and the car was much faster at all rpm.

It is pure physics that you will loose some response in lower revs, but at boost you will have much more power. With a ported head it is normal that you will loose a little bit power in lower revs.
Juergen

I understand your point Juergen, it is usually the result seen. It's very easy to do more harm than good when people brandish a grinder in their ports. It is possible though to do the work that improves breathing without harming low rpm, I see that plain as day when measuring port velocities on the flow bench. Depends very much on where material is removed or left alone! Seat cutting too can vary, a lot.

I should explain an example. For interests sake I worked on a port where I filled it so that the minimum cross section (tightest point, usually just behind the guide on 4 valve chambers) was much smaller than standard. This had the effect of harming measured cfm when compared to a standard port, also, the airspeed through the port (measured with a pitot probe rather than calculated) was greatly faster than standard. The airspeed was way more than an engine could use without choking. Working away at the port gradually I sneaked up on the minimum cross section that a standard port has but still the airspeed was in excess of what a standard port has and in excess of what I considered suitable for improved performance. The measured cfm was more than the standard port at this point. To get the airspeed down to a similar level of a standard port I had to increase the MCSA beyond the standard size which in turn returned an increase in cfm over standard. Size isn't just so important as shape. The sizes were established with great care, molds taken of the ports throughout the work and measured accurately, at least as accurate as I think is possible this side of a digitising probe.