Couple of reasons, coolant in the oil and really bad cross fire at 4,000 rpm and up. Found two microcracks in between the lifters on #5 & #7. The back lobes on the cam were starting to go Tango Uniform. I've got it rebuilt now w/ LT-1 pistons and a roller cam. CR w/b ~ 10:1. Currently rebuilding front suspension and PS.

Well just checked and can't find the rest of my PCV hoses but almost certain that the hose coming from the cannister went to the same hose as the PCV line. The hose you have hilited on mine goes to a tee which goes to a 2 line check valve which then goes to a vacuum source.

MikeC3, thanks again for the part #'s, got the correct stuff today and will try to install it tomorrow.
On my 74 vapor canister I can only see 2 lines, one goes back to the tank and the other "T"'s into the PCV line. Just looked at MidAmericas website none of the ones they show look like mine and I think the third port of yours is just a vent. PG.

The small vacuum hose going to his cannister is what opens the valve that allows the hose going to the PCV tee to suck the vapors out of the cannister.

My third canister line is a larger line and not connected to anything and not plugged. One line definitely goes to the gas tank and the other to the carb. I've been looking at tons of pics online trying to see something T'd into the PCV line and I've never seen one.

I think that other firewall line goes to vaccum. As I was looking through those misc pics online, I found one that I can kind of see that line and it looks like it T's into a vacuum line. Right now, mine is not attached, but a closed line. From other responses, it sounds like it goes to the heater control, but I'm assuming that end of it is connected correctly. I wanted to know where it gets T'd in the engine compartment, and I'm now guessing that it needs to be T'd into a vacuum line.

Thanks!