does the intake manifold have a spacer on a 71 240z? mine has a black one about an inch thick. i have heard that you can get a bigger manifold from a 240k which requires a spacer. could it be possible that it is a 240k manifold?

Manifold bolts to head (with gasket). Spacers between carbs and manifold. Never seen the intake on a 240K so cant help you there. Some of our Aussie and New Zealand members should know. Good luck.

Chris