http://www.turbobricks.com/specs/sohc_heads.php píše:
The Volvo sohc engine has three distinctively types of oem head-designs :
The little one, most common
The big one
And the one without combustion chambers, very rare
The little one:
Oem on: B17-B19-B21-B23 B200-B230
Valves: 44-35 mm, valve seat inserts 46-38 mm.
Combustion chamber dia: 92˝mm, somewhat smaller/narrower compared to the big ones
Height: 12mm
Volume: 51.7cc i.e. 4.3cc/mm
Intake channel: Straight, conical, round, slightly less inner radius
Exhaust channel: A slight hint of a plateau after guide in channel
Casting number, best: 1000530
Other: 100160, 1000398
Potential: Correctly modifyed: Good top-hp with a very good middle-rpm. On little engine hard to beat, indeed.
The big one:
Oem on: early B23E with H/K-cams, B23ET some B230E and ET
Valves: 44-35 mm, valve seat inserts 46-38 mm
Combustion chamber dia: 94mm, a slightly wider layout especially around exhaust, 531 has a little more centered spark plug location.
Height: 12mm
Volume: 53.7cc i.e. 4.5cc/mm
Intake channel: "Swanneck"-shaped, venturi A LOT larger than the small ones, flat and larger inner radius,
Exhaust channel: No hint of a plateau after guide in channel
Castingnumber, best: 1000531
Other: 100405
Potential: Correctly modifyed: Very high top-hp with a good middle-rpm, especially on big volume engines.
The Heron/B230K:
No combustion chamber
Valves: 44-31˝ mm
Intake channel: Swirl induction shaped.
Cast.nr: 1000631
Potential: Due to less experience; no comment
N.B.: All measurements are nominally!
Coolant passages around combustion chambers, valve sizes and CR
The big coolant passages (BCP) give a problem with proper gasket stiffness (even with a uncut head) with combustion pressures significantly above oem pressures...
When subjected to KNOCK/DETONATION or just too high pressure, the area between the coolant channels and combustion chambers flexes/collapses/deteriorates with a resting deformation as a result. When this has happened it is to late to weld an resurface... Only way to use/save a BCP is to restrengthen them via a thorough welding BEFORE pressure-exposure!
The small (desirable) coolant passages (SCP) do NOT flex even when the head is shimmed/cut a lot...!
BCP: All 160 and early 398 and 405:s
SCP: All 530 and 531, some late 398 and 405:s
Valve sizes: Oem inserts allow 46-38 mm valves to be used, although on high heat engines I suggest that larger inserts to be fitted.
Largest valve combination: 50˝-40 mm or a combination thereof (as in 90.5mm included dia).
CR: The oem CR is varied via different S/Q, flat/bowled/domed piston, different combustion chambers (big & small) and different engine sizes.
N.B.: The casting number is placed above and between exhaustports 2 and 3. Manufactured date at side of cyl 4 exhaust port.