I have recently rebuilt a 292 Y block. Once I place the intake manifold on there are 2 holes left uncovered. Is there some sort of a crossover tube? If it is much of anything it will come into contact with the distributor. I have 2 other intake manifolds and they are the same. I have another engine and the temperature sender is on the one side and some sort of plug in the other I will attach pictures if I can. Please send your thoughts.

 

one hole takes temp,sender.the other a small freeze plug

 

The castings are interchangeable left to right. The holes are probably the unused intake bolt holes. You need to plug both with a short bolt. If you use too long of a bolt it will hit the pushrod.

If it is the temp sensor/core plug holes that you refer to, make sure you didn't put the heads on the wrong side of the motor, effectively blocking coolant flow.

 

The mystery was solved the post about the heads being on opposite sides explained it. Never noticed in my haste that that could happen. Thanks for the help.