What is the plug in the bottom of the 289 intake manifold for?

[duo_z]

I'm just curious as to what the plug in the bottom of the 289 4 barrel intake manifold is for? Anyone know.

 

[shoguun]

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[shoguun]

Vaccume probably

 

[2+2GT]

Plug as in inside the engine? never saw one there. Between the carb and bellhousing is the vacuum fitting, for auto trans, power brake, etc.

 

[duo_z]

If you look on the bottom of the manifold there is a sheet metal plate with 4 twist rivets holding it in. If you take that off there is a hex head plug under it.

 

[rbohm]

If you look on the bottom of the manifold there is a sheet metal plate with 4 twist rivets holding it in. If you take that off there is a hex head plug under it.

i think that is for cleaning out the crossover passage that heats the intake when the engine is cold. it may also be just another core plug left over from sand casting the intake so that the sand could be more easily removed. the sheetmetal plate is there to prevent oil from burning from the heat and coking up the underside of the intake, so be sure to put that plate back.