So I've been thinking of disabling the EGR system on '75 455 and from what I've gleamed from the FSM, it looks like if I remove the vacuum line running between the carb and the EGR valve, capping off the connection to prevent a vacuum leak, that would effectively keep the EGR valve from opening, effectively disabling the system. Is this correct or am I missing something?

 

You would be correct.

 

Capping off the connection at the carb baseplate...

 

Yes that works, but the EGR only opens at part throttle cruise. It has no effect at other operating points. If the EGR system is working properly, there will be zero performance difference (however I'm sure the butt dyno will show at least a 2 second improvement in quarter mile times).

 

Just watch out for part throttle pinging.

 

Oh I know it won't give me any real-world performance improvement, I'm just trying to clean up my engine bay some.

Plus it'd be nice if I could keep exhaust gases from depositing carbon and other crap in my intake.

 

If all you're doing is capping the vacuum ports and leaving the EGR valve in place, that isn't "cleaning up" very much. Also, the carbon mainly comes from reversion, which is the exhaust pulse that goes into the intake when both intake and exhaust valves are open at the same time (the overlap part of your cam profile). Removing the EGR isn't going to change that much.