You will definitely never regret having your heads ported and changing the camshaft, I have done this on every motor I've ever owned for the most part from naturally aspirated engines all the way to 1000 hp TwinTurbo set ups. Anytime you increase flow and efficiency, you are able to make more power at a lower boost as you have stated, this keeps intercooler charge temps at a lower level, and allows you to run less timing, let's boost, and make more power on pump gas if you would like.

Also keep in mind that every CNC cylinder head you purchase guys, starts out as a hand ported head. A head is thoroughly hand ported, and flow bench tested for optimal results, then the port is digitized, and then can be duplicated time and time again to exacting tolerances through CNC machining. Once a good porter finds the optimal port design, they usually then have them CNC'd if they have the equipment for this. It is hard for many shops to justify $400,000 in machines just to perform this digitizing and machining task. I myself cannot afford this equipment so I sub the digitizing and a CNC machining out to a reputable shop that does this for me.

I say to go for it, definitely get your heads ported, even if you do not use a different camshaft, you will still have benefits from this, although not as beneficial without the camshaft. Especially if you're going to have the heads off anyway. But keep in mind the cost to install all new guides, perform a valve job, surface the heads, and then have them ported, can easily shoot you up to the $7,000+ range.

I look at it this way though, if I'm willing to spend $7000 on a set of rims, or $20,000 on carbon fiber bumpers, what is an extra 10k put into quality and efficiency inside the engine.

 

Thanks nitro,

So those flow numbers that I have received from CNC company, do they look OK to you guys??
Like I wrote previously, they seem low compared to fx MxKenzie flow numbers.
But how do they compare to numbers that other have seen?
Now that I am having my heads ported, I might as well get a good porting..

 

There is only so far you can push these parts before things get risky with getting fin in certain areas and trashing the head.

If you want to have your heads pushed to the limit, I would recommend using a junk head that you can afford to trash in case the porting goes south( with poor phone numbers, or accidentally going into a cooling jacket). Then once you have it optimal, have it digitized and cnc'd onto your heads.

I'm not sure what is up with those flow numbers from Mckenzie. The ported numbers look OK, but the stock flow numbers are way too low. Every ported head is going to give or take a little bit at certain valve lift, but in the end all seem to flow close to about the same from what I've seen on these heads.

 

For those that have installed ported heads, are these gains only at high rpm, or are you seeing more low end/midrange torque and/or response and/or gains in spool up? I'm not so much interested in peak output as I am getting things as responsive as possible for the type of driving I am building my setup for....

Is the GT3 exhaust cam still the go to, or are those of you with cams running something else? I know with my Supra, you could go slightly more aggressive with the cam (264 duration) and get nice gains in the mid-rpm range over stock.. I don't want power to fall off up top, but I certainly don't want to sacrifice in the 4000-6000 range for gains only seen 6800+.. Unless of course I were to rev to 8000 RPM, but that isn't in my plans/budget.

 

you should see gains all the way through. Biggest gains for on off throttle power and spool time though are filter on turbos, catless exhaust, and Porting the headers and turbine housing. Much more restriction in those than the head itself.

 

how is that an upgrade? I would stay with the GTX.


good heads are the key to making smooth power all the way to red line.

 

7163 far outflows a 3071. Flow is more similar to a 3076

 

maybe on paper or on a subaru, but twin GTX30 will make similar power if not more as the EFRs. I have tried this. def not worth the bother to swap them and i still wouldn't call it an upgrade until proven back to back on the same car.

 

Good to know! Yep I remember talking about that with you a while back! Im full catless, working on a solution for the intake.. Previous owner installed milltek (I think... have the info at home) headers. I've thought about replacing them with the OEMs and porting the OEMs, but will wait until when/if they crack... I've also think to put a thermal blanket on the headers/turbine housing- read of some gains there also.

Anyway, don't want to get too far from the topic. I figure once the car is down for some engine out work in the future, if there are any gains in the heads for my application even if they are small gains, it'll be worth doing.

 

No affiliation with this seller just came across this on Craigslist CNC ported Porsche 996 turbo/GT2 cylinder heads for $6400.00 if anyone's interested? http://phoenix.craigslist.org/cph/pts/5940839874.html

 

OEM GT3, GT3RS, GT3Cup heads. (stock TT/GT2 heads are similar to the GT3 heads)

[url=https://flic.kr/p/rrLTxc]

 

One thing posted I'll comment on as I'm curious.... stated more power at less boost and less heat. Less boost I agree with as there's less backpressure but lower temps? The gauge may show lower boost at the same hp after intake improvements but isn't the turbo still working just as hard? Shouldn't temps remain nearly the same as a result?

John, great shot of the port differences! Do GT3 heads work on our cars, I'm curious! Having what amounts to a factory port might be attractive although I bet the price is nutz

 

I will be running pump gas, and want to make 800whp at max 1,5bar.
So it makes good sence for me to have heads ported and upgrade cams.
I understand that for other setups/plans/goals the money is probably better spent elsewhere.

So the question is not so much to port or not to port - it is more what porting..
Does these flow numbers from the CNC company look ok?
They are lower than McKenzie numbers much of the way.
Low lift and high lift they are the same, but everything in between, McKenzie is considerably higher.
So after some recommendations from those who knows their flow numbers.

See these pics of the CNC ported head. Sure looks good, but I am more interested in how it will perform. How does it flow compared to other ported heads.

 

Blmgk, boost creates heat on the charge side, anytime you can run less boost, the intake air charge will be cooler requiring less help from the intercooler to keep air temps low. This helps keep the air charge cooler, more dense, and makes more power. Hope my jabber makes any sense. Lol


OP, I would ask for before /after flow from each potential porter for the amount you're willing to spend, 15k in porting will get you better numbers than 4K, it's all about time spent. However, the heads can only be pushed so far, so there is a limit without converting to GT3 which a few have done.

If you are leaning to Mckenzie, I would want to know why the stock flow numbers are so low and know what's up with that first. Thats so odd...

 

ok this is something I have a great deal on experience with and I'll try to explain some of it here.
first I'll talk compressor side. Think of a compressor map and efficiency ranges on it. You have flow to pressure on the axis then efficiency in the middle. You take a head or the intake side in general and take a restrictive stock setup verse a modified and ported setup. Looking at making the same hp and flowing the same air volume. Overall sway you're pushing 30lb out of the turbo. On a stock setup it takes 25 psi to do so and on a modded setup it took 20 psi. Now you go back to the compressor map and look at efficiency in the compressor at that flow vs pressure. At 25 psi say it only has a 45% efficiency but at 20psi it's on a 65% range. Since the compressor wheel is running that's much more efficiently, it creates much less heat simply just at the compressor housing.

I'm a exhaust side it's even more important. Drive pressures are really the biggest indicator of your hp limitations. Drive pressures is the psi in the exhaust manifolds that is driving the turbine wheel. Ideally you try to keep it as close to a 1:1 ratio to boost pressure as possible. When drive pressure starts rising far past 1:1 and craps up to 2:1 and I have even seen close to 3:1, you simply start creating more heat and very little hp. Also add huge stress to the engine. This comes down to the turbine wheel size, turbine housing size, and flow of the heads an manifolds. Efficiently getting the exhaust gasses out of the motor. If this system is not running efficiently and your up in the 2:1 range, that back pressure on the motor creates lots of heat. That raises coolant and oil temps. Also add a lot of stress to the engine.

third is turbulence and hot spots. Having turbulence, typically created where things meet and port matching with porting is helpful, creates air spinning, changing directions, and resistance and back pressure at that spot. This then doesn't only limit air flow, but can create a hot spot. I have seen damaged heads that literally melted the casting on the exhaust side ports from this I'm aluminum heads. Even on the intake side though it creates higher intake air temps and decreases overall flow.