Vacuum connections

[Mark80K15]

Hello, I have a 1980 GMC K15 350 4bbl standard. I have a Rochester 4 bbl spreadbore carb. I have a couple questions about vacuum lines that are attached to it. The first is regarding the distributor vacuum advance hose. What is the module that is inline on that vacuum hose? It is circled in red in this picture. The distributor end of that hose is disconnected for clarity.

 

[PrairieDrifter]

That's a check valve as far as I know. Can't say I've ever seen one on vacuum advance.

 

[newguy11]

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[newguy11]

Hope the above image is of some help to you. It’s my 1985 305. It shows that the “module” is likely a check valve as mentioned above. Your lines appear have been modified over the years