So what spec cylinder head to get?

By Clinton HulleyVW Polo Classic Project Car
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I was really set on just building a new sub-assembly, and getting the 8 valve crossflow head rebuilt. But after talking to one of my friends, well my mind started wondering. There was 3 option. Keep the 8 valve crossflow head this would be the easiest. Going 16 valve, well that is a bit more difficult. The 16 valve heads are not easy to get hold off! Then there are the 20 valve heads. There are 2 variants of the 20 valve head. The big port head of the 1.8-liter Turbo GTI golf and the small port head on the 2.0 liter Audi.


I thought the 20 valve head would be the winner. This was a newer design and there were people getting some serious power out of them. I had a friend that had a 2.0 liter 20 valve turbo Audi A3. This car was making around 300kW and like 525Nm of torque. This was serious power at that stage.

I will do a review post on this monster at a later stage.

I phoned one of my contacts to find out if he knew where I could get a 20 valve head. He told me that he had one, but didn’t really want to sell it. The next day I phoned him again and he said he thought about it and he would let it go. I went through to him to go have a look at what he had. It was a small port 20 valve head that came off the 2.0 liter Naturally aspirated Audi engines. A nice thing it has Variable Valve Timing. The big port 20 valve engines in the Golf 4 GTI didn’t have the Variable Valve Timing. The head was in parts but everything was there.


My contact said that he already started working on this project, he had the cams cut to 268 degrees. This was perfect as that was a better spec cam for a boosted engine. So I bought the head from him with a cut-down intake manifold.

An issue with these 20 valve heads was that is wasn’t a straight fit on the older 2-liter blocks. The head bolt holes lined up and the combustion charmers lined up with the cylinders. All the water jacket also lined up. There were 3 oil drain journals on the back of the head that had to be plugged. The block did not have the features to make use of the oil drains. You could only use the back two like on an 8 valve head. There was one oil drain on the front of the head that had to be slightly modified. The port didn’t line up with the 8 valve head gasket.

These oil journals get plugged, I just bought small welsh plugs and knocked them in.
The oil journal gets modified
This is the standard 8 valve gasket on the 20 valve head

There was one more issue that I needed sorting out. The standard head bolts of the 20 valve engine do not fit on the old 2-liter block. On these bolts, the diameter is thinner and it is a different thread. The first issue with the 8 valve head bolts is that it has a flat washer. Secondly, the actual bolt head is too big to fit into the head bolt holes on the 20 valve. What I did was use a grinder and cut off the washers of the bolts. I then put the bolts in a lathe and machine the heads down till it just fitted into the head. The head bolts were long enough to run a thick head gasket.

At the parts shop, I bought all the gaskets and seals I need to build this head.

I enjoyed doing stuff myself, so I decided I will be matched porting a flowing the head myself. Took the head to my friend’s house. He had a compressor and I used his air tool to match the ports to the gaskets. Then I match the manifold to the gaskets. The ports on the head and the manifolds will now perfectly line up. If you look at the intake ports on the small port 20 valve head, the port is restrictive especially on the center valve.

Took most of the material out so that it almost looks like 3 round ports blending into an oval port. I then took the head home and spend a few days on it perfecting the shape of the intake and exhaust ports with 80 grid emery paper. After that, I used 600 grid water paper, then 800 grid until I got to 1500 grid. At this stage, the ports were fairly smooth. Some people say that your intake ports must be rough to help with atomization. I think that is true to a certain extent and it is truer for carburetor cars. As this was a fuel injection engine the injectors atomize the fuel enough. I then took AUTOSOL marine shine and I buffed the ports up so that you could see your reflection it in.

The valve guides on the head were still in good condition with no play on them so I didn’t need to replace them. I lapped in on the valve on their seats as the head was apart for a while and the seats had some rust on them.


Now that the porting and flow work was completed, I had to sort out the cam follower buckets. As it was re-profiled cams, the hydraulic lifters would not pump up enough. This means that the head would be very noisy and that the valve will also not get to full lift. I had to open up the lifters to convert them to solid lifters. Taking out the spring inside the lifter to replace it with a solid insert. I also had to drill a hole underneath the lifter so that the oil that does reach the bucket can escape and not pressurize the bucket. I had to individually measure and machine each lifter insert to get the cam to love clearance right for each lobe. This was a really timely job.

All that was left to do, assemble the head. I gave the head a good wash with the engine cleaner and then dried all the seats. I then oiled them to stop them from making an oxidation layer. Putting the head together was a really trying job as the valve cotters were really small on the intake valve and me not having a proper head assembly bench didn’t help at all.

This project was now really getting momentum and I was really excited, this was going to be a mean-ass machine. The next step was to sort out the manifolds, I was still keen on running the throttle bodies as that just gives you so much better throttle response. So I did some more research…


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