Second PCV with carb "T" or to intake manifold?

[AlexK10]

Hi everyone,

I'm thinking of running a second pcv valve on my 305 to get most of the water/condensation vapors out of the engine asap since I live in a high humidity area and only run the engine for a very short time. I'm fixing a coolant leak in my intake to head surface but would like to add a second layer of protection against condensation (not to mitigate the leaks), this is extra.

I'm currently running a driver's side valve cover pcv valve to the quadrajet vacuum port on the bottom of the carb, and the breather on the passenger side cover.

If I was to run a second pcv valve on the passenger side cover (with new hole drilled for the grommet) and keep the needed breather...

Should I "T" off the quadrajet port I'm using now for the second pcv?

or should I use the npt threaded port on the 5-8 runner with a barb fitting for the second pcv?

 

[AlexK10]

5-8 runner port.

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[ali_c20]

Maybe that's some usefull information:

This is one thing that GM has spent a lot of trial and error on.
After multipe different arrangements, the best setup by far is the PCV in the forward end of the left (driver side) valve cover, & the breather end (or tube to the air cleaner) on the aft end of the passenger valve cover.
This is how you want to do it. Inlet on the passenger side (air sucks in), exit on the driver side (fumes sucked out by engine vacuum & injested into the engine thru the PCV valve).
Since the PCV vavle is a one-way check valve, running 2 wont work.
One more thing to add - since the PCV system uses engine vacuum, it's basically a vacuum leak. So engineers needed to factor that in on carb & ignition design and tuning.
So, the factory PCV system is calibrated. Any changes to the system will effect the calibration. The valve itself may not operate properly if the system is drastically changed.
Running a PCV valve in each valve cover will prevent the "sweeping" of fresh air through the engine, resulting in excessive moisture buildup in the crankcase. It would vent blowby, but would offer none of the other benefits of a PCV system.

 

[SquareRoot]

Change oil regularly and minimize short trips. A second pcv won't add anything.

 

[WFO]

Try not to start your engine unless you plan on allowing it to get to full temperature, so the condensation will steam out.

 

[AlexK10]

Should I "T" off the quadrajet port I'm using now for the second pcv?

or should I use the npt threaded port on the 5-8 runner with a barb fitting for the second pcv?

I guess none of the above. In which case I will leave it as is (front driver pcv/rear passenger breather) and make sure to run it longer.

 

[AuroraGirl]

Perhaps a valve that is more aggressive in allowing it to suck in(not sure how that would work, tbh) but understand its likely gonna suck oil with it.

 

[bucket]

Sounds like a good excuse to drive the truck more. Or maybe when the chores are done, go do donuts in the yard or something before you shut it down. That's what I like to do, lol.

 

[AlexK10]

Perhaps a valve that is more aggressive in allowing it to suck in(not sure how that would work, tbh) but understand its likely gonna suck oil with it.

Or just remove the pcv valve and connect the hose directly to the valve cover grommet with a 90 degree fitting and let it move as much air it wants. It shouldn't suck oil being in the baffled section of the cover.

Or connect a 12v vacuum cleaner to a condensation catch can that's also connected to the valve cover with a timer set to 5 minutes run time after engine shuts down.

 

[AlexK10]

 

[82sbshortbed]

Make sure you have the hose hooked up to base of the carb in front so you pull manifold vacume. It's a stronger vacume and will suck more gasses out.

 

[SirRobyn0]

I'm going to agree with those that don't think a 2nd PCV will get you any benefit. Will it hurt, probably not, but will you benefit from it, probably not. If you're only driving a few miles, I'd rather see you warm it up for a few minutes before you head out so the engine oil gets warmed up before you're done driving. That's the key, no matter how well your PCV system works, it's only really effective when the engine is warmed up. When the engine is cold, moisture and fuel that gets passed the rings when the choke is on gets mixed into the engine oil. No PCV system will stop this from happening. What is suppose to happen is when the oil warms up the fuel and moisture in the crankcase vaporizes and the PCV pulls it out. Without the heat the vaporization never happens. I'm not saying don't do it, just realize it maybe false security. Make sure you have a working Themac and tube on the air cleaner, as well as heat riser, those systems are designed to make fuel vaporize properly sooner, hence more through burn sooner, less unburned fuel passed the rings.

 

[MikeB]

Or just remove the pcv valve and connect the hose directly to the valve cover grommet with a 90 degree fitting and let it move as much air it wants.

No, no no! The PCV valve is only partially open under low vacuum, high load conditions. it's only fully open (in the middle of its travel range) under moderate vacuum, medium load conditions.

With no valve, what you have is a constant large vacuum leak!

 

[AlexK10]

With no valve, what you have is a constant large vacuum leak!

Have to agree on that.

I've reconnected the pcv valve as stock to driver's side cover. Still not ready to start it up again as I have to replace a burnt + battery to starter cable (other thread). Should get this done this weekend and probably start it or the following weekend as I have to work on my daily driver rav4.