I have a 1971 240z that I have been restoring eight years the end of next month 8/13. I had a machine shop rebuild my engine which took the guy two plus years to do. I finally got it in the car and went with thriple Dcoe 40 triple carbs and the engine runs fine. I noticed a month or so after the engine was in the car that there was a small amount of coolant on the block where there are tabs on the block that stick out past the head. I pressurized the cooling system and dropped pressure so I pulled the head off took it to a different machine shop and had them pressure test and put a straight edge on the head and they told me it was good and I told them what happened and who did the motor. They told me the real hard jobs the sub out to the guy that did my engine. The guy that did my engine grew up in a machine shop that his dad owned and the guy is now around 50 and doing engines his entire adult life so he suposably knows what he is doing. I told him what was going on and he said I waited to long to start it and when I did I did not run it long enough. I don't remember his exact words but it's like the head gasket was a rear main seal or something. I alway thought the thing either leaks or does not and told the guy the thing was not a rear main seal or something that drys up. I then pulled the three webers, intake and what not then the head. The guy used a felpro gasket and it looked ok but I bought a new one and installed it, torqued the head to specs and started it again and it appeared fine but a week later I noticed a small amount of coolant along the edge of the block where it sticks out futher than the head. I checked the toque on the head bolts and they are to specs. I am getting pretty frustrated at this point I have spent almost 40k on the car so far and have had everything replaced with new and just when I think I can drive it the leak shows up. If the head was pressure tested and checked to insure it was straight and it still leaks it's got me stumped and a little mad. If anyone can give me some clue other than I waited to long to start the engine which is crap I would really appreciate it.