pcv location,rear of intake, or valve cover

[63.5xl]

I've got some old MT ribbed valve covers I am thinking about running. Does a pcv work any more efficient from the top of the valve cover with the other valve cover having a breather in it than it does leaving it in the rear of the intake when still using the try under the intake? Also will have a breather on tri-power oil fill spout. Or do most of you keep it at the rear of the intake?
The MT's already have holes in them and was going to use some baffled grommets from Moroso  and also the push in breather has a built in baffle that I would hook the pcv to.

[ScotiaFE]

The theory of the Positive Crankcase Ventilation is as the engine warms up to operating temperature
the water will heat up and turn to a vapour and rise to the highest point in the engine.
Which is normally the top of the rocker cover. Then using engine vacuum it is sucked into the intake
track and passed through the engine and burned off.
Sometimes when you see a rocker cover with lots of beige coloured goo in the top of the cover that is the vapour
mixed with oil and it collects at the highest point in the engine.
There are lots of ways to run a PCV system, just some work better than others.
 
 

[My427stang]

IMHO...

First rule of a PCV on something that gets driven regularly is ...  make sure you have one, and that there is a breather on the other side.

Second rule is - baffle or basket.  If you run off the intake, be sure you run some sort of basket or baffle to stop it from sucking oil.  At that point you can run breathers on the v/c or the oil fill tube if equipped.  If you run v/c PCV, be sure oil can't get to the PCV using baffles, or worst case, those little goofy rubber grommets that stop oil splash

Third is not a rule, if you want to go fancy, and the engine doesn't have any blow by, sealed breather to the air cleaner from one v/c, PCV on the other v/c.  This allows ventilation at both WOT and part throttle.  WOT, PCV is at zero vacuum, but any pressure should be relieved through air cleaner.  Part throttle, high PCV vacuum lets it go the other way.  The issue is blowby though, if there is ANY way oil can get into the engine, don't run that breather to the air cleaner, just run a breather.  Oil into the carb makes a mess as well as helping in detonation

[machoneman]

I did just recently read something from an Edelbrock intake installation guide that somebody posted that I've never seen before. They stated that if one had to drill an intake for a PCV source, drill and tap the hole as high up or close to the top of the intakes' plenum, not a runner (i.e. as close to the carb's throttle plate) as possible. I'm not sure placing the source as high as possible this would make a big difference but......... FWIW. 

[nhsohc]

Edelbrock's suggestion is valid as the PCV vapor has to be mixed with the incoming air/fuel charge as close to the throttle plates as you can get.  If the vacuum source port for the PCV is in one of the runners or even one side of a fully split dual plane intake plenum that/those cylinder(s) will go lean and burn something up.  Look around at a cruise night/car show.  Guys are always making this mistake. 
Have seen the PCV hooked to the booster line to the brakes too.  May work OK if the booster line is connected to the carb base but not really the correct solution.

[gdaddy01]

I had a buddy that had a 55 t-bird , with y block , that the brake booster hooked to intake runner on pass. side , rear . it made that cly. dead . moved port location and it cleared up and ran fine after that . He had been chasing all kinds of stuff trying to find the miss . he was very relieved after it was fixed .     

[FE Jonny]

I often wondered if there would be any benefit to running two PCV valves, one in each bank for better evacuation?

[machoneman]

Maybe but I kind of doubt it. It's a controlled air leak and having 2 ports in an intake manifold, one for each, may upset the carb's calibration. It's an interesting thought though Ford would/could have made the single OEM PCV valve a lot bigger than it is, essentially doubling the air flow. They didn't and there must be a good reason why. 

[nhsohc]

Interesting; my '67 428 has a steel line connecting both sides of the intake and then pulling from a single PCV valve located in one valve cover.  The fresh air intake is located in the other cover.