well tis all up and running again.
head gasket had gone on the compression ring on number 3 the ring had a crack in it, and number 4 was about to do the same, strange enuf last time the head gasket went, it was in the same place...... but...... that was also a different head and block, strange.
still maybe next time ill get a copper gasket and then i shouldnt have the prob
does the 200sx DET one for the s12 ??? for furture reference.