Darren Harrold Posted January 17, 2009 Share Posted January 17, 2009 Just been looking around at getting by Duratec Head ported. I see there are some companies offering CNC porting. (Cosworth / Ultmate Performance) Clearly there are obvious advantages to CNC, is there a downside other than maybe cost ? Darren www.csr7.com Link to comment Share on other sites More sharing options...
I.Mupferit Posted January 17, 2009 Share Posted January 17, 2009 You won't do better than AMMO for Duratec porting. Brent (aka Arfur Nayo) Toyota power It's the future! Link to comment Share on other sites More sharing options...
AMMO Posted January 17, 2009 Share Posted January 17, 2009 Darren I have been meaning to write something on Tech Talk regarding CNC heads for some time. Now is a good opportunity to say what I think on the subject. If I had to build thirty engines for a one make series I would seriously consider CNC porting. This would be done to my specifications and not that of the machinist. It would be done because of the man hours involved not because you can get a better result with CNC. I hand ported thirty heads all the same for a one make series once many years ago. I would never do it again. Porting a few heads by hand when required is no big deal. Thirty heads is a pain in the neck. The cost of CNC porting is justified by the cost of the expensive machinery that carries out the work. Just because something costs a lot of money to produce doesn't mean that it is better than something that is produced by hand for less money. Results that are better than a CNC head can be obtained for half the price when ported by hand. The CNC ported heads I have seen have had ports that were on the large side for mixed road / track use. They might have been OK for race engines that are running flat out all the time. I use the best components, like cranks, rods and pistons in my engines because I think they are neccessary. If I thought CNC porting was important I would have CNC porting done to my heads. My advice is have your head ported by hand and save yourself some money. Ammo Raceco.com Edited by - AMMO on 25 Jan 2009 12:27:21 Link to comment Share on other sites More sharing options...
oilyhands Posted January 17, 2009 Share Posted January 17, 2009 I looked into reverse engineering a number of fully ported heads and having future heads CNC ported. Apart from the obvious expense involved there were problems in finding the correct machine/casting centres in all 3 dimensions, if the machining centre were not 100% aligned with the casting centre then what do you use as a datum point? If you sue the machining centre then CNC machining will run the risk of break through, especially when porting in-extremis. If you use the casting centre it may mean the valve throats are offset with respect to the inserts and the ports are offcentre with respect to the manifold mounting. This is a *real* problem especially when factory alignment is not very good. When hand porting due allowance and deference is given to where the metal will be with respect to the casting centre and more or less metal is removed from the appropriate place. As it happened I discounted the possibility purely on the basis of economics, it would have cost a minimum of £700 to rough port a head, plus the cost of the reverse engineering work and CNC programming which would have to ammortises, additionally the head would than have required substantial hand finishing. This would approximately double the cost. A CNC'd head is only as good/bad/indifferent as the model on which it is based, if the model head is not well ported you simply have a very accurate copy of something mediocre. Oily Edited by - oilyhands on 17 Jan 2009 18:53:55 Link to comment Share on other sites More sharing options...
AMMO Posted January 19, 2009 Share Posted January 19, 2009 Oily makes very valid points. When I was unfortunate enough to saying that I would supply 30 heads all the same (they were for Ford CVH, an engine I hate to this day. A lot of work to get very little power) I found out a few interesting things. The heads I was porting came from either Brazil, Germany or England. They had differences externally and seemed to have "meat" in different places. They were different weight. The heavier heads didn't neccessarily have more meat where I wanted it. I had a few heads chopped up to have a look at the sections. They varied quite a bit and some also had inclusions. I had the rep for a company that made utrasonic thickness testers come over and give me a demo. The machine gave erratic readings on the sectioned cylinder heads because of the internal structure of the head so couldn't be trusted. Sections that were a couple of mm thick showed us as having 6mm thickness and vice versa. The machine was made for checking pipelines so wasn't really suited to cylinder heads. So I just ported away and sometimes broke through. Sometimes you could weld the heads up, a couple of times you put them in the bin. The heads can have cores shift in casting which complicates matters even more. With the Duratec I also have had heads sectioned. Heads are also made in Mexico, USA, Japan etc. Lost count of how many Duratec heads I have ported now, quite a few, but to date I have not broken through. There are certain areas where I will not remove material even if it would give me a slight increase in flow. Areas where the remaining material would be very thin and even if I didn't break through it might fail in time due to going through heat cycles. There are two types of Duratec head so the CNC programme for one would not suit the other. With hand porting you can follow the contour of the original port which I find an advantage. The Duratec head is probably the head that benefits least from CNC porting as it is very good in standard form. CNC comes into its own when you have to increase port diamters a lot and you have to do a lot of heads. If you increase the port diameter on a Duratec too much you end up getting great flow at lifts you cannot acheive, 16 / 17mm. You can also end up making power at rpm which exceed the safe redline of the engine. So you have to do a bit of a juggling act. When you increase flow at high lifts you end up decreasing flow at low lifts. You can end up with a head with big ports that actually flows less at the acheivable lift available than one with ports that are correctly proportioned to the valves. CNC porting also removes the guide bosses. This is not neccessary, Flowbench testing shows that boss removal doesn't increase flow on the Duratec. It is removed in CNC heads because the machine cannot go around the boss. This shortens the guide (not good for longevity) and also leaves the guide machined at an angle which makes concentric valve seat cutting difficult (it does on the Sunnen machine at work). With hand porting you can port around the guide boss and leave the guide intact. A guy that went to Emerald with a 2 litre with a CNC head with ports that I think were too that was supposed to make 304 bhp made 255 bhp on pump fuel and 270 bhp on E85. The 2 litre I tested with hand ported head, ported to 280 spec. made 286 bhp on pump fuel. Personally I cannot see any benefits in CNC porting a Duratec. Ammo Raceco.com Link to comment Share on other sites More sharing options...
Darren Harrold Posted January 21, 2009 Author Share Posted January 21, 2009 Some interesting comments. What was most appealing to me about CNC porting is the consistency it should be able to offer based on a template of proven design, even if only minor porting is required. (If jigged up correctly as Oily points out). With CNC I understood that the value guides were removed during the process. If that’s the case, the CNC route would surely make more sense to go all the way and also fit bigger valves. That said, I am not looking for a race engine. My goal is to gain more power at minimum cost; I will not be fighting for every single BHP. Thanks. Darren Link to comment Share on other sites More sharing options...
AMMO Posted January 22, 2009 Share Posted January 22, 2009 Darren If ultimate power is not an issue and cost is, CNC porting is not the way to go in my opinion. Removing the guides to CNC port isn't that smart either unless the guides need replacing. I tend to leave guides alone if I don't need to remove them. There is a chance that if the guides are removed, or even just knocked back, that the seats will need to be re-cut which adds to the cost. If the seats are OK I port around them without damaging them, as not only do you have to re-cut them, but you then have to re-shim the cams as well. Although I'm not in the business of saving the customer money, I'm not in the business of wasting their money either. I just do things the way I would if it was my engine I was working on. As for consistency of ports, after 25 years of porting you get consistent. That is why the power of the engines is pretty much consistent too. Wouldn't go with bigger valves unless you are looking for more than 280 bhp. Stock valves are fine up to this sort of power. 286 bhp is my current record for stock valves. I know from previous posts you are an SBD customer so a lot of the things I say may be different from what you are hearing. As I said in the EWP thread, there is more than one way to skin a cat and neither way of doing things is wrong, just different. Not punting for work (as some may think), just discussing the way I go about things. After all these years of working on engines, cylinder heads and engine developmemnt is something I'm quite passionate about and interested in discussing. Good luck, whatever you decide. Most of all, have fun whilst doing it. Ammo Raceco.com Link to comment Share on other sites More sharing options...
SimonA Posted January 23, 2009 Share Posted January 23, 2009 Hello everyone! I am new to this game of ‘blat-chatting’ and it is breaking a personal rule of mine to get involved in such things but, since the subject matter is so close to my heart, I felt compelled to contribute. So, without prejudice, here goes! First; I must say that I am as bound to talk-up CNC porting as you are, Ammo, to talk up porting the traditional way. After all I have a CNC port machining company and you fettle heads for a living, amongst other things I am sure. Nothing wrong with that of course – I learnt my early trade 20 years ago working at Weslake with the great Jack Cramp – probably the best head fettler there ever was. However, I have also been involved in the development of the most powerful naturally aspirated formula one engines to date which use CNC port-machined heads. They feature no element of port hand-work, other than to deburr, with the potential variability that it brings and you can trust me when I say that if there were any advantage to hand-finishing then the F1 people would do it! Secondly, to counter the argument against the superior performance obtained with CNC porting; we will always be able to produce a better result with a design-driven, machined port as opposed to a hand-generated port since we are able to very precisely control the shape of the duct throughout as required for best engine performance. This is something that is very difficult and time-consuming, although not absolutely impossible, to do by hand. Every month we have professional engine people bring in their best heads to us wanting copies but, in every case, we are able to generate a, sometimes subtly, new design that exceeds the previous best and can be reproduced countless times with speed. There is more to engine performance than flow capacity and port sizes of course but there is no point in getting into a game of ping-pong over this engine being better than that one, especially engines built by others to an unknown specification and mapped by who-knows-who on dynos that don’t correlate with others. Clearly engine results are a function of many parameters and just fitting a good cylinder head doesn’t guarantee a good result by itself. Third, the technical point made concerning machining off the guides is a false one. I do prefer to see a clean, bullet-nosed guide protruding only just into the port, and this is an option we offer, but real flow gains within the normal valve lift range of circa 12mm can be achieved with this approach. Also, our £40k CNC valve seat cutting machine has no problem with machined guides. Fourth; The cost of CNC porting is not so great and is likely to become less so. The cylinder head is the most important part of any performance engine. Save money here and you will compromise the engine’s potential. Money spent on things like electric water pumps is better spent on the top end where it will make a difference. You may be interested to learn that the new Caterham R500 features our phase 1 Duratec CNC ported head. To win this business we had to displace others on both cost and performance in a benchmark exercise. I am glad to say that our head out-performed all others, even a big-valve hand-ported head, but I will concede that we were marginally dearer. I think Caterham’s decision to use us speaks for itself though. We have a number of other high-profile customers recording power levels up to 325bhp from various configurations of Duratec but I can’t mention them here. It is fair to say that, if you buy a top-level UK or Irish race engine, it probably has one of our heads on it! Finally, as we currently produce ported heads at the rate of 200 per year and demand continues to rise - even now - it is fair to say that CNC ported heads are indisputably the way forward - Q.E.D. Ammo, I must say that your reference to our telephone conversation some three years ago rather flatters yourself apart from being somewhat indiscrete. My recollection of it is different but I suppose you can say what you like in these forums to a degree. I mostly agree with many of your published opinions but what I cannot accept is your suggestion that I claimed an ECU bent a crank - I have certainly never made such a claim! Clearly this would be ridiculous and I don’t know where you got the idea from but you should know better than to pedal such nonsense. Please do the decent thing and post a retraction here and nothing more will be said. Any how I must go – there’s a light flashing to tell me another perfectly-ported Duratec head is finished. I might just squeeze another one in before tea-time! Many thanks Simon www.ultimatep.com Link to comment Share on other sites More sharing options...
Peter T Posted January 23, 2009 Share Posted January 23, 2009 This makes for very interesting reading, and i must also agree that CNC controlled machines will allways make a far better consistancy regarding old fashioned ' by hand '. Sure the pair of you can argue about who produces the best head for power but in the end manufacturers want every head to be the same and this is where the CNC wins hands down every time. When you consider that every componet in a car has been designed and built by a PC then you realise that this is what gives us quality, unlike the good old British Leyland days of the 70s & 80s. 😬 Link to comment Share on other sites More sharing options...
AMMO Posted January 23, 2009 Share Posted January 23, 2009 Simon As I recall our telephone conversation was very light-hearted and there was no animosity between us. I don't intend for the situation to change as I have nothing against you or your business. Regarding our differing opinions just let's disagree. You will continue to do what you do and I will continue to do things my way. No problem. Regarding indiscretion, I never identified you, but that was the story as I was told it. By all means give me a call if you want to tell your side. Not looking to make any enemies, just putting my opinions here on Blatchat as Darren asked the question. I think I asked you to quote to have some heads done. Either by you or one of the other companies. By the time I have paid for carriage backwards and forwards and put a margin on the job that is quite expensive, it would cost too much to pass on to the customer. It makes no financial sense as I can port a head by hand for £400.00 with out the hassle of boxing things up. You have every right to voice your opinions and as you have invested quite a lot to produce CNC heads you feel that this is the correct way to do things. I don't agree but there is no reason to fall out over this. Ammo Raceco.com Edited by - AMMO on 25 Jan 2009 12:30:25 Link to comment Share on other sites More sharing options...
SimonA Posted January 25, 2009 Share Posted January 25, 2009 It is no problem to me that we disagree. Anyone reading this thread will make their own opinions on the topic and the case for CNC porting has now been made. Spreading rumour I do have a problem with however. It is not for me to ring you up and explain some story you have been told – apparently by someone else you have now identified by the way - it is for you to completely retract your suggestion concerning me, bent cranks and ECUs. I am not looking for enemies either and I had no problem with you until now – but you will understand that I can’t let someone make public assertions against my competence unchallenged. Let’s get this sorted and then we talk about doing some heads for you… Simon Ultimate Performance Limited Simon www.ultimatep.com Link to comment Share on other sites More sharing options...
AMMO Posted January 25, 2009 Share Posted January 25, 2009 Simon I have been thinking quite a lot over the weekend and was just about to delete the comments which were unjustified. I now realise they were only posted to forward my own case. Had I been on the receiving end of my own comments I think i would have been quite upset by them. What I did was not fair. I recognise this and retract what I said. You beat me to posting by a few minutes. I will give you a call tomorrow to clear the air and chew the fat. Ammo Raceco.com Link to comment Share on other sites More sharing options...
BYKer Will Posted January 25, 2009 Share Posted January 25, 2009 Ammo - I've never met you but given your last post I think you are a gentleman and a professional. Simon- Likewise never met you but glad to have you aboard. Hope you both success in your work seperately and perhaps together, Between you any chance of 300 hp duratech on the cheap? 😬 Will Link to comment Share on other sites More sharing options...
Bricol Posted January 25, 2009 Share Posted January 25, 2009 Question is, how many of us knew it was the other guy, until the other guy went ? Bri Link to comment Share on other sites More sharing options...
Willie. Posted January 25, 2009 Share Posted January 25, 2009 Gentlemen, This is a very interesting topic, and I, and I'm sure others, are very interested in knowing more. Please don't let the thread die. I've ported a head by hand (Die grinder & flexible drive in drill), and I'm a draughtsman sitting on CAD all day, so both ways to port really interest me. I've a couple of questions though. How do you know how much you can remove? By hand is it a case of trial and error or feeling with welding rods? When CNCing, by CAD you can see the best port shape...but how do you know how close to the ideal shape you can go before hitting waterways? How does the CNC machine "centre" the head? Obviously the casting won't be accurate, and you can only go on machined surfaces, which may or may not be identical on all heads; so how do you go about centering the head? Do you locate it by the valve guides or something? Does the CNC machine polish? Or are the ports left with mini machining marks which are hand polished afterwards? I'm not trolling or looking a fight, just genuinely intrigued Willie Link to comment Share on other sites More sharing options...
SimonA Posted January 25, 2009 Share Posted January 25, 2009 Ammo, Fair enough! Let's say no more about it. I look forward to speaking to you again. Simon Link to comment Share on other sites More sharing options...
SimonA Posted January 25, 2009 Share Posted January 25, 2009 Willie, How much metal can be removed is a matter of trial, error and judgement. We section heads to examine the available material and any risks to the casting integrity. With any head you can take more off in some places than others and performance is not necessarily a function of how much metal there is in the bin. The way we port is a bit like doing it by hand but with digital design tools. The Duratec, as with many other Japanese designs, comes with fairly generously sized ports as it is so we remove less matal from these than we do with, say, a Vauxhall XE. When mouting a head on the CNC machining centre a clocking procedure is carried out referencing the fireface dowels to within +/-0.05mm of their nominal position and the head is clamped down. Once set, a double check is made that the valve seats are where they should be and the button is pressed. We do see some casting variation but production heads these days are pretty good I have to say. I think the manufacturers spend quite a bit of time on casting repeatability and original machining pickup. The CNC machine does not polish. You will see the machined finish in the pictures on our website and we are very proud of this. On the whole we do not polish except perhaps where we have left a section of port un-machined for performance/cosmetic reasons. Performance is actually far more influenced by port size and shape than finish. Simon Ultimate Performance Limited Link to comment Share on other sites More sharing options...
Paul Deslandes Posted January 25, 2009 Share Posted January 25, 2009 This was the result of myVx XE head having the Ultimate Performance treatment a few years ago. It might even have been the first XE head that you'd done I seem to remember Simon. I think Simon has further improved the model since then and has been able to get even more flow without increasing the valve sizes which are standard. Needless to say, it transformed my engine together with the inlet manifold being flowed and matched to the inlet ports. Link to comment Share on other sites More sharing options...
Rob Walker Posted January 25, 2009 Share Posted January 25, 2009 Impressive site Simon but £1144.25 for a basic stage 1 porting job on a Duratec head is pricey. Considering that the going rate for a quality hand ported head to stage 1 is around the £500 mark. Edited by - Rob Walker on 26 Jan 2009 08:58:56 Link to comment Share on other sites More sharing options...
Willie. Posted January 25, 2009 Share Posted January 25, 2009 Simon, Thanks for the response. Appreciated. Just while I'm here, would you say its important to open the valve throat up as much as safely possibly on a standard valve head? I've been thinking about making a valve seat cutter type tool to open up the throats but using the standard valves and seats. Or is it not really as important as I think? Willie Link to comment Share on other sites More sharing options...
SimonA Posted January 26, 2009 Share Posted January 26, 2009 Paul, Thanks for that. Yours was XE head #3 done exactly 3 years ago. I have produced 85 more since and have refined the port design further and in 3 different valve size options. It's still the biggest seller but the Duratec is catching up fast. Willie, I wouldn't open the throats up for std valves. More will be gained from a decent valve seat job but be careful not to run out of options on cam follower size. Rob, I think it is good value but then I would wouldn't I! Simon Ultimate Performance Limited Link to comment Share on other sites More sharing options...
AMMO Posted January 26, 2009 Share Posted January 26, 2009 The XE would benefit a lot from CNC porting as the stock ports are far too small for te valve. From memory only 25 mm or thereabouts (as opposed to around 30mm for the standard Duratec port). As it would take ages to do just one head by hand it makes sense to CNC the XE. Simon Tried calling a couple of times today. No reply. Will try again tomorrow at some stage. Ammo Raceco.com Link to comment Share on other sites More sharing options...
oilyhands Posted January 26, 2009 Share Posted January 26, 2009 With the XE and YB Cosworth heads the inlet ports can easily be milled out to 26-27mm with one simple and inexpensive operation, this removes a lot of the laborious work involved in the porting operation. They both start off at around 24mm which is way too small. I have done a good few of each by hand, it is just time consuming. oily Edited by - oilyhands on 26 Jan 2009 19:16:35 Link to comment Share on other sites More sharing options...
CageyH Posted January 26, 2009 Share Posted January 26, 2009 Interesting to see some high speed machining without a coolant. I have not been in a machine shop for a while, but this was surprising. Mind you, I was machining parts from forgings. Only dead fish go with the flow....! Link to comment Share on other sites More sharing options...
AMMO Posted January 26, 2009 Share Posted January 26, 2009 Oily Where I work they do some monster Pintos and some old Rootes engines. The heads go on the milling machine to have the majority of the metal chomped out of the ports. I did quite a few 911 carb heads for racing in the late '80's (911 S or T, can't remember which). They had the first part of the port opened up by milling. Not done that many XE heads. I open the ports at 27mm to avoid problems with breaking through and scrapping the head. Funnily enough I was speaking to an ex-Swindon guy this morning and he used to mill out the first part of the port too. Ammo Raceco.com Link to comment Share on other sites More sharing options...
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