Do you really need a PCV valve for a street car?

[bigmanjbmopar]

Seems mine has oil in it most of the time slight but still sucking it down the carb. Going to take it off and just use a breather on both sides or oil cap. see what happens.

 

[1967 'cuda]

I'd try to maintain the PCV valve. They serve a lot of good purposes. Of course before vehicles had them they used to have vent tubes that released crankcase pressure by dumping it outside of the engines. But some of those vent tubes were designed so that the end was positioned to take advantage of air passing over it to aid in suctioning out that pressure. A lot of oil is being slung around as engines are running. Although we all know it's essential to have decent lubrication not everybody realizes the negative effect that is created at the same time. The pressure will rob you horsepower. It will cause gaskets to leak. In our race cars we built crankcase evacuation systems that would suck the internal pressure out through our header collectors. Windage trays add horsepower by helping to limit the amount of oil being slung. A negative crankcase pressure is supposed to be superior to a zero pressure system. - And naturally a positive pressure is bad news.

Now without breathers being used a PCV valve may not be able to release all the pressure by itself. - And if the check ball gums up in the PCV valve it will be much more likely to start sucking oil out too. Of course more pressure will build up if you're getting a lot of blow by past your rings. I think for the street the ideal setup should contain both breathers and a PCV valve. The bottom line answer is that although it's not essential to keep your car running it does offer benefits and should add to the life of your motor.

 

[Big John]

Yes, you should have one.

The PCV valve keeps fresh air moving through the crankcase... This removes the blow by from combustion and keeps the oil much cleaner.

Old cars had a road draft tube that pulled a slight vacuum when the car was at speed to try to accomplish this.... You also had to change oil a lot more often and the engine wore out a lot sooner. The PCV took care of this problem.

I retrofitted my '53 Chrysler with one.

 

[droptop]

Do you have stock or aftermarket valve covers? Sounds like you do not have any baffles around the pvc valve to keep the oil away from the inlet.

 

[jays69bird]

Some of the aftermarket rocker covers can be tricky.I had a set of the blue anodized Direct Connection valve covers on my Charger ( hey it was the 80's, don't judge !) and I couldn't come up with a Chrysler PCV valve that would work so I used a GM grommet and PCV valve. It never seemed to do the job as good as the stock valve.

 

[bigmanjbmopar]

MP cast covers, just got a new twist in breather so going to try that on a road trip tomorrow. Don't know what's worse oil soaked plugs or dirty oil after a few thousand miles? and yes I have the baffles in place and no my rings aren't bad and no my valve guides are not worn out. Yes carb is a bit rich. I am going to run breathers on both sides see what happens. May have been a bad PVC but it was free when I checked it and worked on vacuum so just experimenting now.

You can hold the hose upside down and drain oil out just a few drops and always seemed to be there wet all the time, seeing that go down the plenum just makes me sick. I know it causing the oil soaking. That and a lot of idling in the garage doesn't help.

So it should get fresh air in one side out the other, see what happens and report back, ran one breather on the drivers side and a oil cap on the other so only one air path in besides the carb lol and didn't notice a difference. my end up going back to the pvc, is the plastic one a good choice?

 

[1967 'cuda]

I've run both plastic and metal and as far as I know neither is better than the other. - As far as those few drops of oil that you've seen... I don't know if that indicates enough of an issue to be concerned about. There are a lot of additives in whatever fuel you run and some of them are there to aid in lubrication. I think that when you consider how much oily vapor has to be vented through the PCV, it's going to at least show a trace.

 

[Big John]

If you aren't running a PCV, then you need to vent both valve covers.

It isn't air going in... The pistons moving up and down compress the air in the crankcase. The idea is to keep that pressure from building up. That will cause you all sorts of issues with gaskets sealing. It doesn't help with getting the rings to seal, burns more oil and in the long run robs horsepower.

Honestly... You may not like this answer but if you are experiencing that much blowby... You have to either live with it or fix the problem.... and that problem isn't the PCV. Some oil through the intake of the engine won't hurt, but not venting the engine properly (especially one with bad rings) will.

 

[bigmanjbmopar]

Went on a cruise today didn't feel any difference. everything drove fine, did notice some smell in the cab for a second at 65 mph but at slower speed didn't seem too bad. Two breathers one on each side.

 

[bigmanjbmopar]

Took a longer trip this afternoon, seemed ok. more smell than last time, thought I saw some white smoke trailing after a 65-100 romp at decel not sure my rear window is so messed up it was hard to tell. When I get time I will check a few plugs see if anything on the plugs got burned off or looks drier.



Think I'm going to play it safe and use one of these. Best of both worlds?

 

[bigmanjbmopar]

Interesting enough pulled a couple of plugs and low and behold the oil was burnt off. wondering if my 493 just doesn't need it. Don't you just love experimenting?

9.6:1 -24 cc dished never has pinged

 

[quikbird]

they make a little baffle that goes on the inside of the valve cover and keeps the oil from splashing into the inlet for the pcv valve. might solve the slight oil pickup problem.

 

[ACME A12]

they make a little baffle that goes on the inside of the valve cover and keeps the oil from splashing into the inlet for the pcv valve. might solve the slight oil pickup problem.

He already mentioned that the baffles are in place...

 

[bigmanjbmopar]

So just to update again. I got those chrome ones, only using the one with the PCV in it. Seems ok and smell seems to be cut down haven't gone on a long trip yet but will soon. Want to clean off the rest of my plugs first.

One thing I liked about this new breather / PCV was that it has the filter inside of it before the PCV so hoping any wet vapor will get absorbed first before getting into the PCV.

Checked out my old PCV and noticed oil on the outside of it where it's rolled like it's failed. Spring and flapper seem ok but who knows?

And yes do have the baffles in place both sides. Push in breather on drivers side and new PCV / twist in breather on the passenger side.





Old PCV shown



Hope it works! if not at least I have a new twist in breather to use as well

 

[criner28]

they make a little baffle that goes on the inside of the valve cover and keeps the oil from splashing into the inlet for the pcv valve. might solve the slight oil pickup problem.

Quikbird, where would I get one of those baffles. Thanks

 

[quikbird]

Moroso, mr gasket, jegs, summit

 

[quikbird]

One part number is 707 r6034. This an example of what they look like. This is on jegs site