Experience of a "lister". See Intake, Exhaust, and Head articles in the Encyclopedia for more opinions.
Since I had the head off, I decided I might as well go for broke. I used the usual technique of marking the intake and exhaust sides of the head with Prussian Blue, then scribing the port opening to match the gasket. (no need to open up the port at the flange, ed) At first I was grinding out the ports with a stone mounted on a 3/8" rechageable drill. This produced a beautiful finish (polish), but was taking far too long. I then borrowed an air compressor and die grinder with some carbide bits and set to work. Whoa! too fast! Had to touch it up with a fine grinding wheel.
DISCLAIMER: While porting a cylinder head does not require the skills of a machinist or mechanic, it should not be attempted by a novice without extreme caution. The best approach for the beginner is to purchase one of the many books on engine rebuilding that include detailed instructions on porting heads, referring to the special points in this document for details specific to the 2.3 litre Ford in the XR4Ti. It is also expected that the reader will take the necessary SAFETY precautions such as wearing safety glasses and hearing protection when appropriate. Grinding produces a lot of metal dust, and I recommend that a filter mask be worn whenever grinding is being done. The author accepts no responsibility for damage to property or personal injury that may arise as a result of using the procedures described herein.
To Start: Remove all components on the cylinder head. On the 2.3 litre engine, compressing the springs requires the use of the large "C" style spring compressor. The shield around the spring makes the use of the small compressor impractical.
The tools you will need for this job include a heavy-duty die grinder, air or electric, various grades of grinding stones, and preferrably carbide bits for fast removal of material. Use the carbide bits (or wheels) with care - they remove a lot of material quickly, and you could easily cut right through to the water jacket or oil passages. Also steer clear of the valve seats and giudes. They are precision machined, and so much as a nick on them can lead to a lot of problems.
Perform ALL the porting completely BEFORE performing the valve grind, just in case you damage the valve seat or guide during the porting process.
The intake manifold presents some other problems. It is made of aluminum, and grinding stones will plug up, and can possibly explode if they get very hot. Use of carbide cutting wheels is mandatory. These will still plug up with the soft aluminum, but this can be minimized by coating the cutting wheel with bearing grease or heavy oil (there is a specal wax just for this, ed).
The intake manifold casting is quite thin on the cylinder 3 port, and may be as bad elsewhere due to casting inconsistencies. If the material is thin, you can coat the outside of the manifold at that point with a two-part epoxy designed for use with aluminum and allow it to set - before you grind through! (the prefered method is to weld up the #2 and #3 injector bosses before proting, ed) You won't be able to clean up the whole length of the intake runners, but the main point of restriction only runs in about 1and 1/2". (Idea Factory has extra long cutters and ports the whole length, ed)
In the valve "bowl" you can use a small grinder to clean up the rough spots, but significant removal of material is usually not necessary, just smooth out the casting. (Flow shaping is important here, THINK before cutting, or see photos elsewhere in the Encyclopedia, ed)
On my own car, I have not done a before and after dyno test, but my seat-of-the-pants feeling is a significant gain in power in the 3500+ rpm range.