hi im considering buying a spare cylinder head and sending it away for a full porting job with new guides etc etc was just wondering whos the best to use for this as the only people iv seen are ktec, prima racing, cgb and gt turbo spares
hi im considering buying a spare cylinder head and sending it away for a full porting job with new guides etc etc was just wondering whos the best to use for this as the only people iv seen are ktec, prima racing, cgb and gt turbo spares
most of those folk only send it down the road to a local machine shop,k-tec do anyway,theres nothing wrong with that,have a look in the local pages for places maybe,or a member could help you do it,we have the adam 005 !!!!
https://www.rtoc.org/boards/member.php?u=765
Try Big Jim Racing. He done a lot of 5GTT work, inc the MSM stuff and for other 5GTT tuners.
I personally wouldn't bother. The gains aren't that fantastic, if any, and certainly not for the money it'll end up costing you.
Manifold matching is worth doing though.
have a read of that mate see if it sways you either way.
http://www.pumaracing.co.uk/Turbo.htm
I would believe it be a mis conception that head work on a r5 is pointless simply becuase its still an internal combustion engine and therefore same principals apply? But im certainely no expert and people on here will have more insight into what gains can be had.Maybe for the money you could see bigger increases of bhp per £ but if you have got everything to the spec you want head work done by the right person will bring you gains!! David Baker owner of the site is currently not undertaking any head work unless you can tempt him with something interesting?
Originally Posted by Mart
tell us more about manifold matching mart.
You just match the head ports to the manifold ports so there's no flat faces obstructing flow. Basically so the head ports match the manifold ports perfectly.
so i guess it would make sense for the manifold to be gas flowed to?
Depends how good a design it is in the first place . A lot of dosh could be wasted on turd polishing
J, if you have a cylinder head, look at the exh and inlet ports...or even and inlet or exh manifold itself...
There is usually a lip, left from the manufacture of the head or part...which can be reshaped, smoothed out and matched as close to the gasket size as possible.
Youre effectively cleaning/opening up the areas after the manufacturing process
Many a modified head work has been carried out on c1j heads over the years, and as I said before, no fantastic gains have ever been found/achieved.
You pays ya money & makes ya choices though.
J, only matching the manifolds is required. Gas flowing the inlet manifold has usually shown a worse result (the air/fuel atomises more efficiently in turbulent conditions; ie, the rough castings within the manifold), and enlarging the exhaust manifold runners will effectively reduce gas pressure @ the turbine, which in turn will prolong spool-up.
I matched mine in my shed with a dremel.
However, over at Track and road one day there was both MSM fastest two cars, the red one that did the 12.18 and Lloyd Bush's that did the 11.9.
Lloyds car made more power, about 244 vs about 235 and had less peaky graphs than the red car. The two engines were near enough the same. They both had head work but the Lloyd car head work went further and was rather good to look at. As soon as I saw that head I wanted it! £400 though.
Having driven Mikes red car, compared to mine there was a significant difference in the way the engine revved. So smooth. My car got a bit rough around 5000 rpm and was not a eager to spin the rpm needle. That roughness was ameliorated by changes and further to the air filter but never as smooth as Mikes. Although I had the Piper 270 and he had a 285, in the end I felt it could have been about the head work, that obviously includes the port / manifold matching and I got all that done but never did that rebuild so didn't find out if just changing the head, and probably also the cam again, would have conferred the smooth effect.
Depends how good a design it is in the first place . A lot of dosh could be wasted on turd polishing
The area round the back of the valve is shocking, it flows about as well as a river with a dam in it. Its got to be one of the worst heads I have ever looked at infact, remove the restriction that is the carb then it might be worth doing a bit of work to the head.
When I was tuning the C1J it would often occur to me that the guys going quicker than 111mph terminals (240hp or more) would have had head work done, usually including larger inlet valves. I concluded it was worth doing in a higher powered car, but certainly not worth while for anyone going for anything less than absoloute maximums. You can make 230hp easilly enough on a standard cylinder head.
Having said all that, I went quite a bit faster than that at 116mph / 260hp with a totally standard cylinder head. No doubt I would have gone better with some work, which would have been my next step if I hadn't of gotten sick of the engine
If you believe RR shpiel, I ran 245hp @ 21psi on Glen T's rollers. That was on a standard head, albeit with matched manifolds.
I still say it's a worthless mod' especially when the carb venturi is in situ; ie, that being the more restrictive part of the equation, but that's just my own findings/opinion.
On my most recent head I just had three angle valve seats, the throats opened and the ports / manifolds matched. Didn't bother with / saved the money from, opening out the ports.
Did also have longer firmer new springs fitted into lowered seats and custom spring caps. Possibly also back cut valves or smoothed anyway to take off the raised edge.
Was going to have the rockers valve top faces ground smooth to go with the taller cam.
Also Jim welded up the chambers and changed their shape so as to increase the swirl. That's a couple of hundred quid extra though. But it did allow Brads 5GTT to make that 240 ish bhp on only about 15 or so psi. Compression ratio maybe 9:1 or higher. The engine felt very naturally aspirated. Very usable around town.
I think that some people like to have a nice smooth usable engine and others just want / require massive power at the strip. In both cases they will pay extra to get that optimisation. Others are not really bothered if their engine is a bit rough or peaky provided it goes and is cheap.
With my Fiat Cinq, people in that world pay £2000 to get the power up to 120BHP from 60bhp.
No 5GTT owner would (intentionally) spend that much for 60bhp! Expecting double the power and three time the torque for that money.
It's horses for courses.
I managed 114 trap @23psi on stock head and venturi, 120 with nos.. i also didnt see much point in doing anything with the head while the carb was sat there being my main problem..
If you are going to have any head/matching work done I'd recomment CTM Performance (should be in the contacts section) they did an excellent job with my engine.
Big Jim would be the one for me, nice and local plus he even told me to save my money and not have work done on my head which was not needed as there would be no gains.
He has alot of knowledge and lots of years of experience
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Jim is actually contracted out by CTM for alot of work. Whether his handy jobs spand as out far as head work, I don't know...
How so?
So basically unless you've binned off the carb for a larger carb or efi head work is pointless and even if you did get shot of the carb, port matching is the only bit worth doing.
Good job I've done both then
seems an interesting read this thanks for the input, one thing i will add is that on my previous 2 cars iv had the heads fully ported etc and both times they made the car much more willing to rev all thru the rev range
Maybe, but did either of those cars have a 25mm restrictor? I doubt it
On which engine(s)?
I don’t know the various 5 engines and arrangements, but each case is very much individual. I don’t really think you can just consider the aspects of the porting (in most peoples books bigger holes, indeed they may need to be smaller in places in some cases, most US 2 valve V8 for example) in isolation. Usually you are also looking at combustion dynamics (fuel atomisation, tumble, swirl, squish etc), gas velocities in the ports, bias in pressure profile, cylinder scavenge, blow down vital to turbo performance, transient response to throttle etc that may be weakness in the original design compromise (assuming these do indeed needing changing for the new application), all of which can be measured and quantified with suitable equipment. However, mostly we are working with older generation engines and so the margins for performance increase are there once the critical points are known in the system, and how changes are going to affect this and resultant packaged performance. There isn’t a single engine manufacturer for performance or passenger applications that now doesn’t pay serious investment in cfd, test, and engine dynamic modelling of such criteria, and you only need to look up the number of SAE articles on airflow and forced induction to realise it’s not without benefit. However, the goals and objectives are highly defined, and emissions and fuel economy are mainly the drivers.
In turbo motors I have generally found that bare port flow of the exhaust at around 80% of the inlet will get the job done. Where as for n/a this would be around 70%, and the main difference being the viscous losses of the higher temperatures. If you have flow numbers for the heads, then it’s easy enough to verify if you really need to be putting massive effort into head work, but unless significant gains are required that efficiency losses and pressure losses can’t be recovered by “another 5 pound”, then money is going to get burned rapidly. Another point is the port flow and cam characteristics need to be considered together, as in many cases the head will out perform the cams capability, as sufficient lift isn’t being reached to take full / if sometimes any advantage of a modified head then the game gets more interesting
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