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melle
V4 Guru

United Kingdom
2283 Posts

Posted - 12 Feb 2013 :  21:18:26 Show Profile Visit melle's Homepage Reply with Quote
I'm currently working on a VeGe 1.5HC engine I recently acquired. It's in good condition and I only have time and no cash to invest in it, so my possibilities are limited to removing redundant material. I'm not after a high rev race engine, but a bit of smoothness and extra bottom torque would be nice. Does opening up the inlet ports (as per S&R specs) in the heads and inlet manifold lead to increased fuel consumption, or does this just guarantee better flow? Valves are in very good condition and will be kept, exhaust ports will be opened up.

1970 96V4 "The Devil's Own V4"
1977 95V4 van conversion project
1988 900i 8V

jdt
V4 Fanatic

United Kingdom
340 Posts

Posted - 12 Feb 2013 :  23:43:21 Show Profile Reply with Quote

Airflow is the secret to power in any engine as if you can flow more air (oxygen) in then you can make more power - that is why 16V engines are more powerful as they have greater valve area

With your std heads I would machine out the exhaust ports and flange to suit the exhaust system (if jetex this is significant amount)
on the inlet 3 angle seats and V6 valves are the best option, if you stay with standard inlet valves the standard head often has a massive restriction below the valve seat and no radius into the inlet port which ruins airflow and can be removed with a die grinder
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melle
V4 Guru

United Kingdom
2283 Posts

Posted - 13 Feb 2013 :  21:00:42 Show Profile Visit melle's Homepage Reply with Quote
Thanks! I've done some further reading on the net and decided to only attack the exhaust ports for now. I have a Jetex on my 96 and I'm considering building an exhaust myself for my 95. I'd like to have something a bit less restrictive than the standard exhaust, but without the Jetex looks.

1970 96V4 "The Devil's Own V4"
1977 95V4 van conversion project
1988 900i 8V
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hillbilly
V4 Fanatic

United Kingdom
225 Posts

Posted - 14 Feb 2013 :  18:57:35 Show Profile Reply with Quote
When you do this Melle will you post some pics as I will be prepping another engine for my 96 (when I finally get it on the road) and would like to work on the exhaust ports to compliment the jetex I have fitted.Your pics will give me a guide.
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Andyinthegarage
V4 Fanatic

United Kingdom
357 Posts

Posted - 16 Feb 2013 :  10:53:43 Show Profile Reply with Quote
I did a spot of light work to my standard heads and noticed that there is often a mismatch between the inlet manifold and the head at the mounting surface. This could remain even after opening up to the recommended SR dimensions. To see it, make up an approximate copy of the inlet manifold gasket from the right thickness of card, put a thin smear of dark grease like molybdenum onto the surfaces of the head and manifold that surround the matching ports. Then assemble the heads and manifold to the engine block and bolt down. Leave for a few minutes for the grease to mark the "gasket" and then remove.

By pushing a pin through from once side of the card to the other, you can show the edges of two galleries as they meet at the gasket.

I then trimmed the card to produce a template which took the lines of the widest point in each mismatch, used this to mark up both heads and manifold and then ground out the overlapping edges and smoothed to remove dramatic changes.

I have absolutely no measure of what the benefit is, but I removed a lip of up to two mil in places which must have been producing resistance and eddies in the flow. It just felt right to get rid!


Edited by - Andyinthegarage on 16 Feb 2013 11:01:43
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melle
V4 Guru

United Kingdom
2283 Posts

Posted - 17 Feb 2013 :  22:24:50 Show Profile Visit melle's Homepage Reply with Quote
OK hillbilly, here we go!

I started marking the new port size (44mm) with a template and a scriber:






Then used my pillar drill as a milling machine (2350rpm):






Realised too late it's not too smart to cut straight down:



My father in law used to be a blacksmith, he'll arc weld the hole up with a dedicated electrode.


Only needs a bit of fine tuning and polishing now (time is up for now unfortunately...):




Old versus new:




Next time I'll do it in two stages. I'll use the tapered bit I used now for milling the port to approx. 41-42mm and a chamfer bit for the rest.


Edit 2/2017: image sizing restored.


1970 96V4 "The Devil's Own V4"
1977 95V4 van conversion project
1988 900i 8V

Edited by - melle on 06 Feb 2017 13:35:09
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hillbilly
V4 Fanatic

United Kingdom
225 Posts

Posted - 17 Feb 2013 :  22:48:49 Show Profile Reply with Quote
that looks about 30% improvement. should polish up quite nicely. I have some of those burrs didn't reailise they are so expensive.
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melle
V4 Guru

United Kingdom
2283 Posts

Posted - 17 Feb 2013 :  23:32:03 Show Profile Visit melle's Homepage Reply with Quote
And that price was excluding 21% vat...

1970 96V4 "The Devil's Own V4"
1977 95V4 van conversion project
1988 900i 8V
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rsimps
V4 Guru

United Kingdom
1616 Posts

Posted - 19 Feb 2013 :  12:51:28 Show Profile Reply with Quote
It takes me about a week to do a full set of heads. They require alot of work for larger valves to flow well. I remove the valve guide (lump of metal that John talked about) out of both ports if the guides are no worn. To be honest you could save yourself some work and only do this on the inlet. The ports are probably a bit small even for the std valves, so a little bit of enlarging on the inlet wont go a miss. The throats need to be a nice round bell shape and you want a very nice smooth short side to the valve seat. Three angle cuts and a back cut on the inlet valve. To do a really good job you will probably need to ship this work to someone with a good valve cutting machine (as what machine it is, Serdi's are good). These give a good accurate concentric seat which helps flow at low lift. If you go to someone that does race engines for v8's eg Rover etc, you might be able to take a stab in the dark at the seat widths and angles used in one of them without flow bench testing.
Ahh just doing a 99 head and finished a full spec stroker rally engine, bliss compaired to the v4 head!
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melle
V4 Guru

United Kingdom
2283 Posts

Posted - 19 Feb 2013 :  13:01:05 Show Profile Visit melle's Homepage Reply with Quote
I'm not after a full spec race engine, just trying to improve a bit on standard with the tools and knowledge I have at hand. Trying to improve on the latter here, so thanks for your feedback!

1970 96V4 "The Devil's Own V4"
1977 95V4 van conversion project
1988 900i 8V
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rsimps
V4 Guru

United Kingdom
1616 Posts

Posted - 20 Feb 2013 :  12:08:02 Show Profile Reply with Quote
Put it this way I use the v4 std valves in my skoda and that flows enough for around 120 bhp, so actually there is some merrit in making best of what you have got for a fast road car.
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