71 Valiant,
I hope you have better luck with that problem than I am having.
My breather was smoking like 2 packs a day...the previous owner hid the blow-by problem.
My Duster ran great, other than keeping the engine bay lubricated, supposedly 5K miles on a complete rebuild.
Engine had great vacuum.
I did a compression test and got 145-150 psi for each cylinder.
Did a leak down test and my cylinders were leaking at a rate of 55-60%...not good. The breather whistled like a tea kettle full of boiling water during the test.
I pulled the engine and have it on a stand waiting for me to pull a piston or 2 out.
Looking at bad rings or ring gap, bad assembly or maybe bad machine work.
My wife said no spending $$$ until after the first of the year...hopefully this won't bust my piggy bank...and wind me up in divorce court.
Good Luck,
Paul