Derek 328 ,
There are a few different heads
400 with 85A engine N322030
85C engine N322030 with tube inserted into centre throat to
block balance tube , also some fitted to early 401
401 all with 85C engine N322040
The stamped engine number of these 85 engines/heads are between 1001
and 2292
The 100/110 series heads have larger diameter inlet ports & inlet valves
403 with 100A & AB2 engine N322080 with # 3000 - 3300
404 with 100B &C engine N322690 with #3501 - 3634
405 with 100B2 engine N322080 with #3700 - 3838 & 4001 - 4341
406 with 110 engine 110-1-2002 with #5001 - 5204
Pls note there are some variations in the detail above and often there are large gaps in the engine numbering system.
There are also heads fitted to Bristol Sports engines 100D,100D2, FNS & BS
What car / engine will you be fitting one to , ans what type of use will you give it ??
I noticed you have a Frazer Nash BMW 327 , I suggest any 85 series head would be more suited to that engine than the 100 series head. But if you want it for an engine that can rev as high as 6000rpm a 100 series head might be more suitable .
I have had 85 series engines/heads that will go to 6000 rpm with minor porting and slightly larger inlet valves (depending on cam,compression and carburation). The smaller diameter inlet ports increase the air speed and mid range torque.
When inspecting a head check for corrosion around the water transfer holes and the amount of previous machining of the bottom face of the head .
My recommendation is to buy the one in the best condition .
Good luck in your search.
Geoff
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