If you go with a new cam remember that you will need to fit new tappets. These are the buckets that run directly under the cam, and anecdotal evidence suggets not using pattern parts here. I know of a couple of people who used pattern folowers that shattered at high revs locking the cam solid and filling the sump with nice sharp shards of hardened steel. The Porsche ones are sit down expensive, but there again none of mine ever let go. I did my cylinder-head in 1992 and prices then were;
Cam, from PMC, £235. Don't see PMC about much now.
Tappet
Porsche sourced £38+ vat per bucket
Audi sourced £52+vat per bucket.
Pattern part £19+vat.
You pays your money and takes your choice.
I used to use 6,200 as a rev limit. It would wind up to 5,700 quite quickly, taper off a bit, reach 5,900 and then go on to the maximum without straining. The best acceleration I ever achieved was using 5,600, 5,800, 5,600, and 5,600 as change up points. You need the extra between second and third because of the biger step up in ratios between them, other wise it used to bog down a bit until it got 'on the cam'
As an indicator of what to expect, in a direct comparison between my 924 and my 944s, tested between two fixed points, the 944s would show an indicated 110mph, and the 924 would indicate 107. I reckoned about 140 bhp. I never had a problem with drivabilty with the cam I used. Many a Golf gti and Vauxhall astra found out to their cost how effective a set up it was.
I worked for a company called Autocavan, many many years ago, (in the late seventies) and we specialised in tuning VW engines. I learned all my skills there so I did all the flowing work myself. I have absolutely no idea how much this would cost, and I cant remember off hand how long it took me. However, I still do have the cylinder head with the cam in it, but it has now done 100,000 miles, so it could do with new stem seals. You might want to get in touch with Bert Gear, he is most likely going to have a contact or two in that area.
There have been so many books writen on modifying heads that you ought be able to do it yourself, much cheaper, if you want to work to the lowest budget. We are not racing, hence not looking for perfection, so don't worry about getting the flow rates for each cylinder to match exactly. You will need some internal callipers, and invest in a good quality electric die grinder, and only use tungsten carbide cutters. Use copious quantities of parafin as a coolant, which also helps to stop the cutter clogging with aluminium swarf. Obviously the head needs to be off the block. Additionally, it is also much easier to do with the guides removed, and changing them is absolute childs play.
The easiest thing to do to start with is match the ports.
First spray WD 40 lightly into the waterways around the ports. If this starts to smoke, stop, you is getting mighty thin.
INLET
Put the gasket(s)on to the port-face on the head and mark the outline with a felt-tip pen or other marking method. Remove material to this outline and blend in the profile. Do the same on the mainfold.
EXHAUST
Do the same, but it's a bit more laborious as the manifold is cast iron. It is interesting to note that the 924 already has a cast-iron 4 into 2 (inners and outers) exhaust manifold which aids breathing, but there is a whopping great lug inside it which can be removed.
Anyway in the interests of keeping this post short I am going to stop there. You have a number of options open to you, so you need to choose which one is best for you. As it stands I might take £100 for the head, worth it for the cam alone which is in good condition having been run on synthetic oil all the time, but you will definitely need the shims for the tappet clearances as, again, on a limiterd budget I didn't fit them, and I would recommend new guides and springs for the best perfomance, although it will bolt straight on and run. It will be a bit tappety, and you will lose some of the extra lift and hence performance because of the excessive valve clearances. When I rebuilt the head the only things that weren't renewed were the vavle-spring seat thrust-races, and the guides, although renewed, are still standard size, but as I have already mentioned it has 100,000 miles on it now. With two 924 turbos I don't need the head. If I don't sell it then I will fit it to my aging 924 lux before I sell that later in the year.
