[v2rocket_aka944]

Head can be shaved for more compression but it doesn't do a whole lot for you. IIRC the max you can shave is about 0.060". The wear spec is in the Haynes book. You measure the head thickness with a caliper between the head surface and the little cast pad on the front corner of the head by the coolant gooseneck.

Pistons are all the same from 82-87 NA in USA, 88 they were higher compression ratio bumping power from ~143 to ~152. Those pistons are prized by the racer guys so they come at a price.

Camshafts can be bought from WebCam, Elgin, and John Milledge in the USA (if you can get a hold of John Milledge, he isn't easy to reach!). They typically give up some of the low-end performance in exchange for 5-15HP at the high end, but no one seems to have any dyno sheets to share to prove the gains, although Milledge insists he has tested his.

Balance shaft placement is actually pretty easy - the gears on the ends can go on two ways but you align them with two steps - there is a notch on the back lip of each of the gears that has a TDC mark that lines up with a notch on the rear belt cover. On the front face of the gear is stamped a "0" which should be visible at about the 11 o'clock position on the upper balance shaft and about 5:30 on the lower balance shaft when both gears are set to TDC marks.

The easy way to set belt tension is as follows: grab the longest span of the belt (between the crank gear and the cam gear on the timing belt, without the idler installed; between the upper shaft and tensioner on the balance shafts, without the idler installed) between your thumb and forefinger and twist the belt. The timing belt should be just tight enough that you can turn the belt 90 degrees between your finger/thumb and no more. The balance belt is looser, you should be able to twist it about 180 degrees around with your finger/thumb.

The belt job is really a lot easier than some people make it out to be. Take your time and note all the little steps as you do it, but once you've done it a few times you can just go off memory. I have done so many cars that I can take my time on an NA and have a running car with new belts in about 2 hours.

Honestly...the Haynes book has almost every spec and instruction you could need for rebuilding the engine and maintaining the car. Only a few procedures require other information and you are well-served there by Clarks-Garage and the forums. It's really the best, most-useful $15 you could spend to learn about the car.

As far as performance modifications, I can tell you the following as the ultimate, best bang-for-your-buck mods to make your car way more fun to drive. Some people will tell you to strip weight but I would advise against removing carpet/sound deadening unless the car is just a toy for weekend street driving or track days. You will hate the car with no sound deadening if you drive it often/daily.

0) make sure the engine is well-maintained in good condition, runs well, etc before modding anything.

1) Weltmeister/other brand throttle body cam (available here on Pelican, PN# PEL-PP-905837). This changes the way the throttle opens relative to gas pedal position. The stock Porsche throttle cam is a piece of s**t and makes the car feel ridiculously slow at anything under full throttle. the Weltmeister cam truly changes the character of the car and makes it a lot more fun/easier to drive. They are about $28 new, or you can take your stock throttle cam and cut off the long leg to make it approximately circular in shape for the same effect.

2) MAF conversion. I like Rogue-Tuning's NA-tune MAF kit (roguetuning.com). It truly transforms the car. You gain a little bit of power at the peak end (5-6 whp) but WAY MORE power/torque everywhere else in the RPM range. The car runs smoother at idle and has way more "pull" at all RPMs. I dyno'd my car before/after the MAF conversion and gained from 10-14 wheel ftlbs from 2000RPM til about 4000. You can cruise along at 2000rpm effortlessly with the MAF whereas the AFM setup requires a lot more RPM/throttle. The Rogue MAF conversion is $500 or so and worth every single penny.

3) Only944 shifter setup (Only944.com). The Shifter lever update with the bolt and thrust bearings makes the shifter feel a lot tighter in your hands versus the sloppy worn out stock item. It can be improved even more with his short-shifter setup and solid-link bar so there is almost zero play in the shifter, just nice, smooth, perfect gear placements. The shift lever/short shifter setup is around $150, maybe less, I dont remember off hand.