How does this happen?

[marni]

Rebuilt RB25DET 

Lets skip to the juicy bit, this is my head after max 2km of testing, not running well before, thought valves may be the issue but they seem ok. Comp is at 140 (I know it's low)

this is the intake side, no soot anywhere else, just in this one spot

what the fk could've caused it?

thanks 

Marni

[KiwiRS4T]

140 compression is fine - the question is what is the range of compressions 1 - 6?