Help Identify part/resolve issue

[Junkie]

Hello. I am doing some upgrades to my 77' (new valve covers, sniper, headers/exhaust, fuel system). There is this part at drivers rear and passenger front of the block. I assume something to do with emissions. Neither have been hooked up to anything in quite some time. I was going to remove and cap them off but the first bolt snapped. What are my options for capping these off if I snapped the bolts? Maybe just fill in with black high temp silicone? Thank you for your help.

 

[Oldtimer]

That is a thermactor air pipe used inject air into the exhaust system, to control emissions.
When I removed them on my 68, I sealed the ports in the heads with freeze plugs.
If the bolt snapped off far enough below surface you may be able to install freeze plug, but it may be difficult with out removing heads.

 

[Junkie]

That is a thermactor air pipe used inject air into the exhaust system, to control emissions.
When I removed them on my 68, I sealed the ports in the heads with freeze plugs.
If the bolt snapped off far enough below surface you may be able to install freeze plug, but it may be difficult with out removing heads.

Sounds good! Thank you for the solution!