I was working on my 71' Roadrunner tonight and I sat here scratching my head over this canister. I'm guessing this is a vacuum canister for something. The car was built in california. Problem is my car is an original 4 speed with manual HD drum brakes. So what the heck would this thing be for. It is located under the battery tray. I know the that the master cylinder in the pic is not original. That's cause I've got the original in a box while this replacement is used just to give the car braking power.

That is the same location as a 70 B body a/c vacuum canister.....does your car have A/C? If so, the mystery may be solved.

Air grabber?

Yes the car does have AC. Why would the AC need a vacuum canister?

Air grabber canister is not mounted under battery tray on any year B body. All of the doors on the a/c system are vacuum operated. The vaccum can helps response time for the system as far as I know. Would also hold a bit of extra vacuum when car is shut down.

So I just gotta figure out then where the two line hook up.

I got my old man over here saying he's never heard of that. He thinks its supposed to be a direct line to the manifold to operate the AC, without a canister.

70-71 Parts Book
Slave Circuit Vacuum Control Reservoir
P/N 3441532 71 B-Body

From the 70 FSM

Thanks a bunch! Been flipping through my CD parts manual for the past 2 hours and couldn't find it.

It should have a check valve in it. Dont hook it up backwards.