SP72 Posted August 23, 2018 Share Posted August 23, 2018 Gents Has anyone undertaken intake or exhaust port matching as part of a rebuild? Costs are high (£150/port), but has been recommended to me to smooth out port flow on both intake and exhaust sides. I want to maximise gains from the bigger headers and ITBs but don’t want lose low/mid range. I think the intake side change should be relatively minor, as the 3.2 ports are 40 or 41mm, whereas the ITBs are 42mm. I think the biggest change would be on the exhaust side - BSM have recommended smoothing the step from 38mm to 42mm in the pic. Pros and Cons? Does anyone know why the step is there on the standard setup? Shirish Link to comment Share on other sites More sharing options...
Dr Rock Posted August 23, 2018 Share Posted August 23, 2018 Had the intake manifold-cylinder head holes blended on my rebuild and the SSI’s matched to the exhaust hole size Link to comment Share on other sites More sharing options...
SP72 Posted August 23, 2018 Author Share Posted August 23, 2018 2 hours ago, Dr Rock said: Had the intake manifold-cylinder head holes blended on my rebuild and the SSI’s matched to the exhaust hole size Thanks - what were the advertised benefits? Link to comment Share on other sites More sharing options...
Dr Rock Posted August 23, 2018 Share Posted August 23, 2018 (edited) No idea: GCR just did it as part of the build. Probably something to do with boundary layers and swirls and stuff like that I guess. Edited August 23, 2018 by Dr Rock Link to comment Share on other sites More sharing options...
mean in green Posted August 23, 2018 Share Posted August 23, 2018 It's all about getting gases out smoothly and efficiently isn't it? Check out Andy Perk's Ark thread. He DIY ported his with a die grinder in his shed, along with flowing the webs, mooning cylinders, radiusing valve cut outs, boat tailing, weighting pistons and a tonne of other little tricks that took him up near 300hp. Link to comment Share on other sites More sharing options...
Beaky Posted August 23, 2018 Share Posted August 23, 2018 Isn't that part of an engine rebuild normally referred to as "Honing and gas flowed" the heads? Link to comment Share on other sites More sharing options...
Dr Rock Posted August 23, 2018 Share Posted August 23, 2018 1 hour ago, mean in green said: flowing the webs, mooning cylinders, radiusing valve cut outs, boat tailing, weighting pistons and a tonne of other little tricks GCR did all of that as well Link to comment Share on other sites More sharing options...
SP72 Posted August 23, 2018 Author Share Posted August 23, 2018 1 hour ago, mean in green said: It's all about getting gases out smoothly and efficiently isn't it? Check out Andy Perk's Ark thread. He DIY ported his with a die grinder in his shed, along with flowing the webs, mooning cylinders, radiusing valve cut outs, boat tailing, weighting pistons and a tonne of other little tricks that took him up near 300hp. It is, but I don’t understand the impact of it all. Is it good for road cars or just trackday/ competition cars Link to comment Share on other sites More sharing options...
jevvy Posted August 23, 2018 Share Posted August 23, 2018 4 minutes ago, SP72 said: It is, but I don’t understand the impact of it all. Is it good for road cars or just trackday/ competition cars its just another place to make a small gain (or rather get rid of any potential small losses). Certainly not needed and there are probably other things that would give you more bang per buck. Link to comment Share on other sites More sharing options...
Chris T Posted August 23, 2018 Share Posted August 23, 2018 Agreed, more bang per buck elsewhere, but for the racing boys where mods are restricted, every BHP counts. Shirish, please do no do this....! You have a great engine, have spent, I don't doubt, a small fortune. Enjoy the car, drive the nuts off it and forget about porting, boat tailing, half mooning etc.... As always, my 2p. Chris. Link to comment Share on other sites More sharing options...
SP72 Posted August 23, 2018 Author Share Posted August 23, 2018 Jev, Chris - input valued, thanks Would it ever make sense when going from a bigger port to a smaller port (intake) rather than a smaller port to a bigger port (exhaust) I was contemplating it as the heads are coming off again in October, but it’s an expensive exercise. Link to comment Share on other sites More sharing options...
Beaky Posted August 23, 2018 Share Posted August 23, 2018 Be careful you don't end up with a car with great BHP and Torque that you can't drive and enjoy on the road! You still need to be able to put all that power on the ground and then stop it and if you look around most big BHP air cooled and wide bodied as well. If you wanted real power and stall have that analogue driver feel dare I say it, a 997 GT3 gen1 for around £80k would be better. Link to comment Share on other sites More sharing options...
Chris T Posted August 23, 2018 Share Posted August 23, 2018 From what I've read/understand, smaller Vs bigger port, intake and exhaust sizes give more torque Vs more BHP. You decide where you want the power. Blending however has got to be good, smoothing the airflow can never be detrimental* IMHO. Chris *TOO smooth an inlet used to be said not to atomise/swirl the fuel/air enough but I don't buy it with modern injectors. Link to comment Share on other sites More sharing options...
Beaky Posted August 23, 2018 Share Posted August 23, 2018 Or put another way, is say another £5k worth 3-5bhp particularly if you don't like the end result, that investment isn't coming back! Link to comment Share on other sites More sharing options...
Chris T Posted August 23, 2018 Share Posted August 23, 2018 May be up to 10bhp I reckon but that is still £500/hp..... Where does it end? Just enjoy the car. Link to comment Share on other sites More sharing options...
ALEX P Posted August 23, 2018 Share Posted August 23, 2018 SP, I did some of this when doing my engine. Basically I mooned my cylinders and did some simple windage work. It's half way down page 12 of my thread: I think that all the little bits such as port matching and windage do add up but I certainly wouldn't be paying big bucks to get it done as I really don't think the bhp/£ ratio works well here. For a rough idea of what engine machining work should cost it's sometimes worth using Rob Walker's guide as a yardstick: http://www.robwalkerengineering.co.uk/porsche.html Dude, I'm not gonna lie to you, I think you've lost the plot a bit and are running out of ideas of how to spunk money on this engine build. I just wrote a load of negative reasons why then deleted them as it's not really any of my business so I'm just going to butt out. I have always really wanted to see a happy ending to your build but can't help thinking its got a bit out of control. Link to comment Share on other sites More sharing options...
SP72 Posted August 23, 2018 Author Share Posted August 23, 2018 Agree Alex to an extent, but just trying to understand pros/cons of various new suggestions, which were not mentioned earlier in the design phase. Ive now read what peeps are saying about port matching, but I wouldn’t have known the answer if I hadnt asked the question. I’m not trying to spend money, as frankly, there’s not much to spend. Just trying to ascertain the cost:benefit ratio of these new suggestions as I won’t be taking it apart again Link to comment Share on other sites More sharing options...
Beaky Posted August 24, 2018 Share Posted August 24, 2018 (edited) Honestly Shirish, this sounds like a Katie Price saga, each time she visits the plastic surgeon he says, I can add a bit here, snip there, pump up those, etc etc. now look at the mess she's in both physically and financially! I think there is general concern out here buddy. I think it's inherent in an engine builders nature to always push the boundary, look at what's the next evolutionary, experiment by adding different components to the mix and being the guinea pig has its risk! Seriously you need to draw the line on this before it gets more out of hand, just fix the known issues and enjoy the car. Edited August 24, 2018 by Beaky Link to comment Share on other sites More sharing options...
strosek34 Posted August 24, 2018 Share Posted August 24, 2018 Sounds a lot of money to me, I agree with the other get using it. I do understand why you asked as that's the way you learn stuff. Back in my olden days you had to drill and dowel inlet manifolds to the head so they always bolted back in the same place otherwise you would get some mis-alignment. You used engineer's blue and then ground out the orifices until they matched head to manifold. I used a good old black and decker drill Link to comment Share on other sites More sharing options...
sopor Posted August 24, 2018 Share Posted August 24, 2018 9 hours ago, ALEX P said: Basically I mooned my cylinders 🤔 😂 Link to comment Share on other sites More sharing options...
SP72 Posted August 24, 2018 Author Share Posted August 24, 2018 Come and join me folks on my imminent ‘is twin plug worthwhile?’ thread. Link to comment Share on other sites More sharing options...
Beaky Posted August 24, 2018 Share Posted August 24, 2018 40 minutes ago, SP72 said: Come and join me folks on my imminent ‘is twin plug worthwhile?’ thread. In that case add "take it to 3.8 or 4.0" thread..................................................... Link to comment Share on other sites More sharing options...
Busybee Posted August 24, 2018 Share Posted August 24, 2018 I’d have thought a good engine builder would have included gas flowing in his build to be honest. Particularly on a high performance engine like this with lots of upgrades. Sounds expensive SP. Benefit, few more hp. Downside, another grand or two and another month or two indoors. If you have the cash and the inclination and are happy to keep fettling/waiting rather than driving, go for it Shirish. Moi, would have been back on the road and melting rubber some weeks ago. My SC is stock as stock gets. I flippin love it. It’s about how it makes me feel, not the biggest, baddest for me. I’ll just go light another joss stick and do my yoga 🧘♀️ 😂 The 4.0 Carrera I had a passenger ride in was immense though. Like being kicked up the arrrr5e by Bruce Lee or running into hulk hogan. Awesome acceleration/stopping power. I vividly remember hanging in the harness during breaking with just my feet to support me on the footboards lol. So I can see why some get the biggest thrill from an extreme build. Go in peace grasshopper 👍🚀🏎 Link to comment Share on other sites More sharing options...
David Gander Posted August 24, 2018 Share Posted August 24, 2018 Agree with Chris and Beaky........it can get out of hand as the analogy to Katie Price suggests....mega bucks for a few BHP?....might even be negative if the swirl pattern doesn’t suite?......consult the Gods and with a small offering, just sleep on it, the answer surely will come in a dream possibly? Regards, D. Link to comment Share on other sites More sharing options...
angusb Posted August 26, 2018 Share Posted August 26, 2018 On 8/24/2018 at 11:28 PM, David Gander said: Agree with Chris and Beaky........it can get out of hand as the analogy to Katie Price suggests....mega bucks for a few BHP?....might even be negative if the swirl pattern doesn’t suite?......consult the Gods and with a small offering, just sleep on it, the answer surely will come in a dream possibly? Regards, D. +1 on David`s comments. Porting is not a Diy job,as you need to know the exact shape to cut.On a old Mini, porting liberated more power ,as Austin had not bothered with the head casting. Porsche ,being Porsche, did a proper job. Fiddling about with porting , at the very best, is just a waste of money. Link to comment Share on other sites More sharing options...
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