richyb
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| posted on 23/9/08 at 12:06 PM |
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Cylinder head Porting BHP
Anyone any ideas/experience with basic DIY head porting - how easy, any easy guides and how much extra bhp to expect ?
i am thinking of a winter upgrade on my zetec - fitting throttle bodies, but thought i may try this as well.
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Mr Whippy
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| posted on 23/9/08 at 12:20 PM |
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One of the easiest things to do is match the inlet manifolds to the inlet ports on the head. You just need some blue die, clamp them together then
grind away the mismatch, apparently (according to Volksworld) this can equal the improvement of going from single to dual carbs.
Fame is when your old car is plastered all over the internet
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bimbleuk
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| posted on 23/9/08 at 12:46 PM |
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Yeah buy yourself a couple of spare heads, make a DIY flow bench and read a couple of guides. Then spend many hours experimenting!
Or just stick to matching the ports as above and remove obvious steps and casting marks which should make gains but not necessarily that much.
When I had my 5 valve head flowed by a specialist I specifically asked for exhaust port gains. They did exactly what I asked but the amount of work
invovled was substantial including work on the ports, seats, vavle stems, guides, combustion chambers and water ways for good measure!
Below is my flow bench graph and my dyno result was a gain of 142 BHP to 165 BHP and 115 lbs ft to 125 lbs ft from a 1587cc engine.
There should also be a couple of pics of the flowed head in my archive.
 
Standard v modified 20V cylinder head flow chart.
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bimbleuk
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| posted on 23/9/08 at 12:50 PM |
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Sorry I should say the dyno figures benefited from a very mild exhaust cam as well but only 10 deg more duration and 1mm more lift as ultimately the
engine would be supercharged. The head like a lot of modern multi-vavle engines have restrictive exhaust ports for most likely emission reasons. The
flow bench figures are from a bare head, no valves or cams etc.
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02GF74
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| posted on 23/9/08 at 01:30 PM |
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what the Whipmeister said, perfect job for the ong nights ahead.
(I used a scriber to mark the ports).
before:
 
v8 inlet before
and after:
 
v8 inlet - after
wow - was that really 4 years ago!!?
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zetec
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| posted on 23/9/08 at 02:04 PM |
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I did my zetec with a dremel and course sanding bands. Ali is soft and easy to smooth casting marks, standard head does have a few lumps and bumps.
Also so as said get the manifold ports matched. Also a good chance to lap valves and replace guide seals. Remember ali dust is nasty stuff for wear a
face mask!
I'm sure if nothing else getting the valves lapped will improve things, and porting will give best results with a cam upgrade. I also changed the
big end shells although even after 70,000 miles they were still in very good condition.
 
Rescued attachment DSCF0130.JPG
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Rod Ends
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 posted on 23/9/08 at 03:51 PM |
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Read David Vizard first!
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