PCV Valve Or Breather

[mikester]

Getting ready to start on the 81 again and I have to place a Summit order.
How many of you guys are running a PCV valve ? I have a breather on one side of the 406 and planned on putting a PCV on the other side. Now Im wondering if I really need it. Should I just use another breather ?

 

[565bbchevy]

I run a PCV valve on my Regal with a 355 SBC and a vacuum pump on my Monte with the 565 BBC.

 

[airboatgreg]

Unless you have a low vacuum engine you need both. The PCV(Positive Crankcase Ventilation) pulls air from the other side of the engine to relieve crankcase pressure, condensation and other gases. The carburetors are metered to allow for that metered vacuum leak. I always use an AC Delco PCV valve

 

[ck80]

Unless you have a low vacuum engine you need both. The PCV(Positive Crankcase Ventilation) pulls air from the other side of the engine to relieve crankcase pressure, condensation and other gases. The carburetors are metered to allow for that metered vacuum leak. I always use an AC Delco PCV valve

Regardless I'd always run a PCV...

Breather always gets rid of positive pressure so that's a wash, but, the pcv actively pulls out the vapors that combine with moisture to form acidic compounds and promote sludge formation.

If anything, I'd argue that in the ethanol fuel era with heightened water content in gasolines that a PCV is more important now than it ever used to be.

 

[64nailhead]

If you're motor is fresh, then a PCV will help develop and maintain good ring seal. On the other hand, if your motor is an oil leaking, high blowby deal then definitely DO NOT run a PCV due to the end result is alot of oil ingestion from the PCV.

 

[abbey castro]

I have a ZZ4 using both the PVC valve with a breather on the driver side and the vent tube to air cleaner base.

 

[Ernest]

I have a ZZ4 using both the PVC valve with a breather on the driver side and the vent tube to air cleaner base.

Same engine.... my PCV in on the driver side by the #1 cylinder connected to the 3/8" pcv connection on the front of the carburator base plate and a breather on the passenger side by the #8 cylinder.

 

[57 Handyman]

I hear a lot about PCV and the reasons for having that system on a motor and what it does. I agree venting and getting rid of any moisture, water vapor which results from combustion is a positive. My motor is a fresh rebuilt 350 with vintage 57 dual quads. There is only a single oil filler tube with a breather cap and no rear vent tube next to the distributor...as in 265-283 motors.

As with anything regarding SBCs, there are pluses and minuses in everyone's opinions. One claim I keep hearing, in particular, is the PCV system helps relieve pressure in the crankcase. Pressure build up in the crankcase would lead to oil leaks. I'm guessing that the main source of any crankcase pressure build up would be from piston/compression blow-by. But in a newly built motor this should be minimal.

All that being said, I've not heard exactly how much or even any suggestions on a range of pressure that can build up in the motor. Any ideas? Thanks in advance.

 

[64nailhead]

Leaks are secondary. Cylinder seal is the primary reason for PCV.

Race cars run open breathers because of frequent rebuilds and the bulk of the time is at WOT. But street cruisers should adopt the exact opposite mentality.

If you intend to put a fair amount of street miles on your car, then a PCV is a must S well as a proper breather. Both work in unison.

 

[57 Handyman]

Thanks for your response 64. This car is my 87 El Camino and will live on street with only the "heavy foot" WOT experience for sheer enjoyment to impress others! As a retiree, there will be some daily driving and going to local cruz nights here in the islands. I can address acid buildup due to moisture with more frequent oil changes. However, I am concerned about crankcase pressure resulting in oil pan and timing cover leaks since changing gaskets in these areas are a pain in the butt. As many of us envision, we see our kids enjoying these vintage vehicles once we leave the scene.