One Blackened one not?!? - 912 Cylinder Heads

[tjbates]

I am trying to see if this is from the factory 'normal' or if the engine has had a replacement head fitted?

Upon striping down a Porsche 912 engine I noticed that one is Blackened and one is the normal alloy.

The part numbers are both the same 616.104.301.02

Photos here:

https://goo.gl/photos/mi8k5kukf7EYjiKX9

Thanks.

[KS]

The black one looks like somebody's painted it with 'heat dispersant' paint or engine enamel, so I'm guessing one head's been replaced at some point. Definitely not from the factory in an unmatched pair like that.

[Kneeslider]

Some heads had the black coating from the factory, but I thought that this was confined to S90 heads? Also the stamping between the combustion chambers should refer to the chamber volume. I have no idea what the typical variance from the factory was, but 60 and 61cc is quite close, I am not sure if that is close enough for factory tolerances.

[Jesse]

S90 had the black ones

[Mike Smith]

Black Heads - S90`s and SC`s (possibly some C`s)
912`s - I don`t think so - but no doubt some one will correct me

Check that the Valve sizes are the same on both heads

[KS]

Every day is a school day. Thank heavens for old blokes like Mike to teach us youngsters...

[Mike Smith]

C - SC and 912 Heads
Inlet Valve Head Size = 37.9 to 38.1
Exhaust Valve Head size = 33.9 to 34.1

S90
Inlet Valve Head Size = 39.9 to 40.1
Exhaust Valve Head Size = 30.9 to 31.1

Other Dimensions also vary but this should give you a clue as to what heads you actually have

Ease up Keith I`m only 76 - years in me yet ?