There are different heads B202, B212, B234 (longhead), B204 (shorthead), B234 (shorthead)

B202 asymmetric ports
SAAB Part no: 752170
Intake port (height, width): 28 mm,38 mm
Exhaust port (height, width): 27mm,42 mm
Combustion space volume: - cc
Flow intake: - CFM
Flow exhaust: 160* CFM

B202 OG asymmetrical intake

B202 OG asymmetrical

B202 OG asymmetrical

B202 OG asymmetrical combustionspace

B202 symmetric ports (old generation, with oil feed pipes)
SAAB Part no:-------- 
Intake port (height, width): 28 mm,38 mm
Exhaust port (height, width): 27mm,42 mm
Combustion space volume: - cc
Flow intake: 153* CFM
Flow exhaust: 160* CFM
<picture of head>

B202 symmetric ports (new generation, no oil feed pipes)
SAAB Part no: 9107376
Intake port (height, width): -- mm,-- mm
Exhaust port (height, width): -- mm,-- mm
Combustion space volume: - cc
Flow intake: 182* CFM
Flow exhaust: 165* CFM
<picture of head>
<picture of intake port>
<picture of Exhaust port>
<picture of combustion space>

B212 & B234 "longhead" 
SAAB Part no: 911535
Intake port (height, width): 31 mm,43 mm
Exhaust port (height, width): 27mm,42 mm
Combustion space volume: - cc
Flow intake: 192* CFM
Flow exhaust: 170* CFM

B212 head

B212 intake

B212 combustionspace


B204/B234 (T5)  "shorthead" 
SAAB Part no: --------
Intake port (height, width): -- mm,-- mm
Exhaust port (height, width): -- mm,-- mm
Combustion space volume: - cc
Flow intake: 228* CFM
Flow exhaust: 17x* CFM
<picture of head>
<picture of intake port>
<picture of Exhaust port>
<picture of combustion space>

*data from Group9

Springs
The springs.

A	Min 19.6 mm	0.7717 in
B	24 mm	0.9449 in
C	Max 28.4 mm	1.1181 in

Specs (source SAAB 900 workshop manual, 0 technical data):

Length, mounted	37.0 mm	1.46 in
Length, free	45.1 mm +/- 1.5	1.77 in +/- 0.05
Length, loaded to  595-645 N (131-141 lbf)	28.4 mm	1.12 in

The stock springs are good for up to aprox 7000 RPM.

Tappets
The tappets are hydraulic and does not need any adjustment.


Tappet

Specs (source SAAB 900 workshop manual, 0 technical data):

Diameter	32,959-32,975 mm	1.2976-1.2982 in
Height	26 mm	1.02 in
Bore in head	33,000-33,016 mm	1.2992-1.2998 in

The stock tappets might start to "float" at aprox 7200 RPM.

Valves
The valves are precision made and is not needed to be replaced unless they are worn or damaged. 

OBSERVE! the valves are stellite covered, and shall not be machined! In some porting recommendations a back-cut is done on top of the valve to increase flow. This is not recommended on stock SAAB valves.


Valve guides
The guides are made in really durable steel.

*Measured with the valve extracted 3 mm (0.12 in) from the seat 

Intake
The B212 has larger ducts than the B202. Which gives more flow. 
Intakes must be port matched to the cylinder head. If not the turbulence created be hard ridges will be a big problem.

B202 intake


B212 intake (polished)


Comparison between B212 (left) and B202 (right) 
.

Porting 1 on 1
Porting, opening up the "in and out" of the head to ensure more and/or better flow.

B212 head cross-cut
There's a "rule of thumb" whilst porting and sizing up the valves and ports.

1. Measure Bore
2. Use the following "formula" for Hemi Heads:
----------------
intake valve = 0.55*bore
intake port = 0.8*intake valve
exhaust valve = 0.8*intake valve
exhaust port = 0.8-1.0*exhaust valve

So lets size up the B202
Bore = 90
 
Which gives

Intake valve = 49.5 (stock valve = 32 -> 1.5 times smaller)
Exhaust valve = 39.6 (stock valve = 29 -> 1.3 times smaller)

This shows that according to the "rule of thumb" there's a lot of possibilities to increase the flow. But mounting larger valves aren't easy and requires special tools. so to the "regular" Joe, it's not the first option. And I've seen cars that have been "dyno'd" with over 500 hp with the stock valves. 

But remember that higher valve lift will get increased flow through the valve openings. So at "hotter" cam is a good step in the right direction.

But when we got a "hotter" cam and want even more flow... then there's a way to increase the flow with a little work. Porting!

Remember this when porting: 
Start with the intake. Check how much opening up of the ports are possible. Make a template of the intake mount (this will also be the gasket template) and put it on the cylinder head to see if it's possible to do that port-job. If it looks feasible then mark the Cylinder head ports to measure out the outer limits of the port-job. This is the port matching. Do the same on the Exhaust manifold.

Start with a "hard" grind stone to grind down the valve guide or replace the guides with other canted ones (if replacement is at hand, mount the  new guides after the port-job is done). Then switch to a carbide burr (oval or flame shaped) and start opening up the ports. 
Remember to have lubricant (French chalk, kerosene, or WD-40, I recommend WD-40) to help the flutes from clogging.
IMPORTANT, there are waterways and other hollows in the head so don't grind to deep. 

When the base shape of the ports are done. Use Different sanding papers (like Flap wheels, slot-shaft with paper and plain paper and finger) to work yourself to the finished surface quality.

Never ever have a perfect shine on the intake side of a Cylinder head! Droplets of fuel might form on the walls and drip into the cylinder. Atomised fuel and air mixture can be compressed. Liquids cannot! (not easily, though). This can actually harm the engine. So make sure that the intake port is glass blasted or similar. This will help the air not to stick to the walls and the flow will be better. This is just like a golf ball. A golf ball with grooves will fly longer than a smooth one. Some professional "porters" actually makes some small groves in the head behind the injectors mounts just to make sure that the needed turbulence will be formed.  

Case study, B202 Head
----------------------
Port, step 1. 
Don't port! get a B212 head to start with.

B212 gasket mounted on a B202 to show the difference

Case study, B212 Head
----------------------
Port, step 1. 
Regrind of the valve guide and polishing of the ports.

Stock intake


ported intake

What has been done on these pictures are:
- Grind of Valve guides
- Polish of ports

Case study, B212 Head
----------------------
Port, step 2. 
Regrind of the valve guide and grind & polish of the ports


Stock intake


Comparison between step 2(left) and step 1(right 

What has been done on these pictures are:
- Grind of Valve guides
- Grind of ports (opened them up a bit and removed the valve guide ridge)
- Polish of ports .

Case study, B212 Head
----------------------
Port, step 3. 
Regrind of the valve guide and major port-grind & polish of the ports.
<comparison picture of stock exhaust port & step 3 >
<comparison picture of stock intake port & step 3 >
<comparison picture of stock comb-space & step 3 >
<close-up picture of grooves >
What has been done on these pictures are:
- Grind of Valve guides
- Major grind of ports (opened them up much and removed the valve guide ridge)
- Polish of ports
- Grooves made to ensure turbulence.

Case study, B212 Head
----------------------
Port, step 4. 
Regrind of the valve guide and major port-grind & polish of the ports.
Larger valves


Tools of the trade:
The following tools is needed:
- Multipurpose grinder (Dremel or similar)

Dremel
- Grinders
<picture of oval burr>, <picture of flame burr>

Flapwheels


Grinders


Here's a really good book on the subject!
GET IT WHILE YOU CAN!
It's out of print!

How to Build, Modify & Power Tune Cylinder Heads