oadamo
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| posted on 13/6/07 at 06:25 PM |
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head porting
hi anyone had there zetec head ported as a mate of mine that drag races cars said that he would port my head.so ive gave it to him and hes told me ill
need a new inlet manifold and exhaust manifold.
because of the size.he said the inlet ports would end up about 45mm. that sounds f**king big to me from what they are. but iam thinking of using the
car just for the 1/4 mile now lol. has this happened to anyone on here you start off trying to keep it cheap then you start going mad with parts
lol.
adam
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bimbleuk
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| posted on 13/6/07 at 06:43 PM |
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Maybe some confusion over what he was describing as the Zetec valves are something like 32mm so the inlet ports wouldn't be much bigger. Maybe
he was refering to the manifold runner size?
On my 1600cc Toyota engine the individual throttles are 45mm on the later 20V engine and that works fine.
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Confused but excited.
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| posted on 13/6/07 at 07:00 PM |
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" has this happened to anyone on here you start off trying to keep it cheap then you start going mad"
Yes we all bought a book about building a car for £250. 
Tell them about the bent treacle edges!
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speedyxjs
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| posted on 14/6/07 at 07:13 AM |
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quote:
Originally posted by Confused but excited.
Yes we all bought a book about building a car for £250.
How long can i resist the temptation to drop a V8 in?
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02GF74
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| posted on 14/6/07 at 08:48 AM |
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quote:
Originally posted by 02GF74
there is no way he could be referring to valve size; as you can see, inlet can go maybe 1 or 2 mm in size but not 10 mm or so.
There is no advantage making the ports much bigger than the valves as the valves become the bottleneck? Mayne the inlet port tat the manifolds was to
what he was referring to - I'd geuss the are of that be 2x that of the vlave diameter.
 
Rescued attachment zhd.JPG
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Browser
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| posted on 14/6/07 at 09:11 AM |
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45mm sonds liek an awful big port. Then again, it is a 16 valve lump so I wouldn't want to say yay or nay.
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DarrenW
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| posted on 14/6/07 at 10:29 AM |
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The way i read it is ref matching the inlet / exhaust manifold holes to the head. Although not great i dare say its better to have the head ports
smaller on the exhaust side then flowing into a larger exhaust manifold, maybe a bit of a bell mouth on the head. However if the inlet manifold exit
ports are larger than the heads inlet part then the air would hit a step. I wonder if the first inch or so of the head can be bell mouthed to give a
smoother transition and avoid the need for buying extra bits.
Do i understand the quandry properley?
Of course a true sized match would be preferential but cant imagine Henry's crew would have made the std kit with such a mismatch.
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bimbleuk
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| posted on 14/6/07 at 05:38 PM |
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Remember the runners are feeding 2 ports in and out of the head so 45mm wouldn't be so large. On my 20V 4AGE eaxh 45mm throttle body is feeding
3 26.5mm inlet valves!
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oadamo
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| posted on 14/6/07 at 07:59 PM |
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iam going to see him tomorrow so hopefully it will be done. ill post some pics.
he has a flow bench in his shed. hes the one that flowed my diahatsu head for me some years back. but this time i think hes gonna go wild he said that
a mild port job was a waste of time because the ports become an obstuction lol the way hes talking. i think i will deffo have to go turbo fill them
up properly lol. i just hope he doesnt f**k it up
adam
[Edited on 14/6/07 by oadamo]
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MikeRJ
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| posted on 14/6/07 at 11:17 PM |
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Monster inlet ports can give disappointing results on a road engine. Low gas velocity means you can lose torque at the low/mid range which will
already be worsened by a hot cam. If you aren't fitting a hot cam then hogging out the ports to such an extent makes even less sense.
I saw a Dunnel Zetec head that made 180bhp from a 1.8 silvertop. Whilst the ports had clearly been cleaned up, they certainly weren't greatly
enlarged. Just for reference that was running on Jenvey TB's, Emerald ECU and a pair of Piper cams. For bhp/£ that makes the XE look even
better IMO!
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