I just picked up a rebuilt Rochester 4MC carb, code #7042251 for my 72 Cutlass with a 350. I have confirmed that the 2251 of the code designates the carb was for a 455. That’s not a problem. My question is this: Can I cap off the vacuum ports that won’t be used without any issues? I’m specifically referring to any vacuum port related the EGR, EEC canister or anything else that is no longer being used. I should add that the engine currently has an Edelbrock 1406 600 cfm carb with only the PCV valve line routed to the carb.

 

Yes, you can cap off any vacuum port you are not using.

 

As has already been stated, not only yes you can cap off any vacuum port you are not using, you most definitely should cap off any vacuum port you are not using otherwise you'll have a vacuum leak.