The 2 litre 16v head cutaway and maximum porting dimensions thread.

[Brian.G]

Back to the wire again, you'll need two pieces 60mm long and 65mm long, point tips as before and from the tip mark the 5 points with 11mm between them.
Track around as before.



You should be left with this when finished, apply paint to grooves finishing in white at the straight end.



Thats the datum jigs made!!
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SETTING UP THE JIG AND USING IT TO REFERENCE THE MEASUREMENTS LISTED ABOVE.

Right, first, give the intake face of head a good clean with water paper or a fly cutter in a milling machine.
Insert two studs into lower holes that are used to affix intake manifold, one stud either end of head.
(in my case head was cut so i used to holes near each other, you wont have that problem!)



From the side of this stud mark a line 28mm up, this is your datum line for setting the jig and also the mid-way position of port mouth.



Scribe a light line along head.



Like so.



Now the stems.



Insert into guide from the bottom up, MAKE SURE the red marks indicating when the hole is pointing straight out, parallel to each other.



Using a piece of 3mm stock(if you used 3mm for the position pieces this will work perfect)set the stems 3mm shallower than head face.
You could do this a number of ways I guess but this is the handiest I think using parts on hand.
Perhaps tape on a rebated block to head face to ensure they stay exactly 3mm back, I set them once and they dident move afterwards. You just need to make sure they are 100%, easy.



Insert wires into holes, remember its the long set of wires.



Place strip on top making sure you centralise it on all the saw cuts on its edges in relation to port width, and line the cuts in the ends on the scribe mark you just made.



If you have a scrap head now is the time to fill the countersinks around wire with soldier OR if its a good head and you fear a torch may warp it, use a two pack epoxy in there they dont take much holding really.
Im going to soldier mine as ill be using this tool many times.

You can now see with the jig in place measurements can be taken in seconds with the inside callipers, and the great thing about it is for most porting work you can leave the stems in place and just pull strip and wires as a unit once soldiered giving you instant access to get the burr in there again for any fine tuning.
It is important though to make sure stems dont move out of reference when checking specs, they wont though as there's no work on them, but double check every time.

[Brian.G]

SETTING UP THE EXHAUST JIG AND USING IT TO REFERENCE THE MEASUREMENTS LISTED ABOVE.

Insert two studs into lower holes that are used to affix exhaust manifold, one stud either end of head.
(in my case head was cut so i used to holes near each other, you wont have that problem!)

From the side of this stud mark a line 30mm up, this is your datum line for setting the jig and also the mid-way position of port mouth.

Please note the jig must be setup on port two, port one being at the belt end.


Scribe line at port centres as done on the intake side.



Insert the two stems into guides from the bottom up, MAKE SURE the red marks indicating when the hole is pointing straight out, parallel to each other.
This time you must set studs 12mm back from face of head.
You could do this a number of ways I guess but this is the handiest I think using parts on hand.
Perhaps tape on a rebated block to head face to ensure they stay exactly 12mm back, I set them once and they dident move afterwards. You just need to make sure they are 100%, easy.



Insert wires into holes, and place strip on top, remember its the longer wire thats goes on the right.



Soldier or glue, put a red mark on the left hand end of jig.



Place in vice and cut at approx angle as show taking into account where the red mark is in the picture, cut must be exactly on the centre of strip, cut down to to port width mark.



Cut out the little triangular piece, do this both ends, be careful and make sure you dont bend wires.

Should look like this when done.



The purpose of cutting ends out at an angle is because jig has to be inverted for measuring ports 3 + 4.
Ports 1 + 2 are mirror images of 3+4 so to save making two jigs these cuts at ends make it possible for the jig to be used on all four.
If they weren't cut the strip wouldn't allow datum wires to enter port straight as the strip would be kicked on manifold face.
See below, the angle cut allows jig wires to enter at correct angle, same as before, just make sure you keep it on your port centre line.



An easy way of knowing if you have jig the correct way round is just check to see if red dot is pointing to centre of head and not towards the flywheel or belt ends.

Thats it Guys, your now ready to take your measurements and start checking where the material can be taken out of, Im going to spend the next while filling in the co-ordinates so you can use them for reference.
I still need to pick a safety margin, ill post safety margin too when I come up with one Im happy with.

The jig is real easy make, describing how to make it actually took longer.
Remember, make it as accurate as you can, after all its pretty basic but the measurements must be adhered to.

[Brian.G]

Exhaust side specs up tomorrow.
Came across this on my travels:

''VW 16v head:
The VW 16v head is a performance nightmare. I think VW introduced the
head merely to say they had one, as they obviously didn't care about
performance when they designed it. VW began design of the 16v head
about 1980. It went through various metamorphasizing phases before
it was released. On one version, the exhaust cam was gear driven,
but VW ultimately chose chain drive because it was the quietest way
to drive the exhaust cam. (The quietest way they would consider;
they obviously chose not to allow the exhaust cam to be belt driven
with the same timing belt as the intake cam...which would have been
the quietest by far.) According to my sources, VW was planning to
introduce the head as early as 1984-85, and some 80000 units were
produced. Then it was discovered that some engineer forgot to design
water in the casting around a pair of exhaust valves. Overheat =
cracked head ==> junk 80000 castings <==> put the program back a
couple of years.

Before the head came out, rumors were circulating as to its design
characteristics. All of us in the high performance business cringed
at what we heard. We heard that VW had designed the head with the
exhaust valves top dead center over the combustion chamber; the
intake valves cocked over about 20 degrees. We said if that was true,
the head was junk. We couldn't believe VW (read that ANYBODY) would
introduce a high performance head with such awful flow characteristics.

When I saw my first 16v head (off the motor), all my nightmares turned
into reality. Actually, it was worse than I thought. The exhaust valves
were top dead centre, but the exhaust ports exceeded a 90 degree bend
to allow the gas to exit. This head was obviously not designed for
performance. The valves spacing is too close together, thus putting
in bigger valves would be near impossible. The only possibility of
obtaining higher performance was porting and polishing.''