I have a 2000 Gen VI 454 L29 Big Block with Oval Port Heads, and when I set the intake manifold down it sets on the china wall and the gap between the heads and the intake is bigger than the gasket I have for it. Does anyone know why the MPI intake seems to small for the area?

 

Are you saying the intake is sitting on the block end rails before making contact with the cylinder heads? Are you sure about the block being a Gen VI? And are the heads the large oval ports, or the small square port, or the large square port. Sorry for all the questions but in the Big Bock family there are quite a few different combinations. Have you personally witnessed this engine assembled and running or did you purchase the parts separately?