What are the advantages/disadvantages of doing this? Should I do it?

 

Might depend on if you have F.I. or not, If you live where it gets cold and have a carb it will make the engine take longer to get to operating temp. I have a 69 Cuda with it blocked and have to let it warm for a few minutes before I can drive it, before I blocked it I could drive right off pretty quickly, It did seem to pick up a few hp by doing it.

 

Blocking it off helps keep the intake manifold cooler, helping to keep the air/fuel charge more dense and therefore producing more power. It also increases cold operation issues for a street car.

If you need functioning EGR, then just block off the driver's side. You'll maintain the operation, but reduce manifold heating.

If you don't need EGR and aren't worried about gas pooling in the plenum during cold operation, block off both sides.

Last two seasons, I had one side blocked on the 396 (had a manifold-mounted choke thermostat at the time I put the manifold on). When I put it back together this spring, I blocked off both sides (gaskets didn't have the holes, actually). I like it better this way for my use.

 

Thanks for the info guys. I think I'm just gonna block it off.