Are PCV needed?

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scott69dart

scott69dart

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Need some advice, I just got my 69 Dart on the road and have discovered oil saturating the Summit Breather on the right valve cover located to the back of the valve cover. Have oil running down onto the headers. Valve covers are the Mopar Performance ones. I cleaned the breather and have relocated it to the driver side valve cover which puts the breather towards the front of the valve cover. The cloud of smoke has stopped on acceleration but is this the solution. The other valve cover I've been using the typical 1/4 turn cap.
Question, should I be using a PCV valve on the right side in addition to the breather on the driver side or use a PCV and cap the other side? Seems like the passenger side gets oil slush toward the back of the valve cover or maybe a push rod points right at the hole in the valve cover allowing oil to be squirted into the breather???
 
It wouldn't hurt to run a pcv valve. The older the motor the more pressure it's gonna build in the block. Is there a baffle under the breather. I d vent and baffle both sides or connect a pan evac if you are running headers. Pressure in the block is rough on seals. Pushes oil thru guides and past crank seals.
 
A good PCV system aids in ring sealing. I would not run without it.
 
500stroker said:
It wouldn't hurt to run a pcv valve. The older the motor the more pressure it's gonna build in the block. Is there a baffle under the breather. I d vent and baffle both sides or connect a pan evac if you are running headers. Pressure in the block is rough on seals. Pushes oil thru guides and past crank seals.
Click to expand...


The motor is new, sort of, all new rings, bearings, block was hot tanked, Cylinders were in great shape, cleaned and reused original pistons. Summit cam and manifold package (mild cam). Oil pressure is 65-70psi when cold, and when warm and RPM is run up. Around 35psi at idle when warm.

I'll go ahead install a PCV valve and I'll have to check to see if there is a baffle in the valve cover holes. Thanks
 
I am running those covers on my smallblock. I had that problem also. The problem was the baffles that come with the valve covers has 3 holes for screws to attach it to the cover and for some strange reason there is an extra hole right where the oil filler hole is on the cover and the oil goes up through it into the breather and saturates it and then runs out onto the cover. I made another baffle without the extra hole and have not had this problem since. As for the PCV valve, it is a good idea to use one to help pull extra pressure from the engine. But you can also just use a breather cap on each cover and be fine, done this myself and seen many others like it. If you decide to do the PCV valve DO NOT cap the other cover, put a breather on it. I decided to do this on my car and made that mistake and oil went everywhere. Now I am going to have to pull the engine and put a new gasket set on it. I only made it about a mile down the road when the smoke started, opened the hood and oil was everywhere. After it happened I started asking myself why this happened then it hit me, all factory cars have the pcv valve but the other side had the vent going to the aircleaner and they have an oil cap. Still kicking myself for that screwup.
 
The right way to do this is to have a breather PLUMBED TO the air filter bonnet on one bank, and the PCV on the other bank. Also, if you have any sort of smog inspection down there, that is the way it must be plumbed--no breathers open to the air

I agree though, that many MANY aftermarket covers have a REALLY poor baffle setup

I'm still using the old aluminum (Cal?) covers I bought in 72. I'm using a Ford twist on filler/ breather combo for a breather.

Like this one, I hope not this price. The fitting on top goes to your air filter

http://www.semomustang.com/store.aspx?panel=3&productid=606&categoryid=240

Oil_Breather_Cap_-_ChromeFHEJ.jpg
 
duster360 said:
I am running those covers on my smallblock. I had that problem also. The problem was the baffles that come with the valve covers has 3 holes for screws to attach it to the cover and for some strange reason there is an extra hole right where the oil filler hole is on the cover and the oil goes up through it into the breather and saturates it and then runs out onto the cover. I made another baffle without the extra hole and have not had this problem since. As for the PCV valve, it is a good idea to use one to help pull extra pressure from the engine. But you can also just use a breather cap on each cover and be fine, done this myself and seen many others like it. If you decide to do the PCV valve DO NOT cap the other cover, put a breather on it. I decided to do this on my car and made that mistake and oil went everywhere. Now I am going to have to pull the engine and put a new gasket set on it. I only made it about a mile down the road when the smoke started, opened the hood and oil was everywhere. After it happened I started asking myself why this happened then it hit me, all factory cars have the pcv valve but the other side had the vent going to the aircleaner and they have an oil cap. Still kicking myself for that screwup.
Click to expand...


Okay, I think I have it solved, found the old PCV from the donor car parts box, cleaned it up and it works great. Install it on the passenger side and a breather on the driver side. Drove it on my usual test run, nice long uphill highway at 60 -70 MPH and no smoke and no oil sign of oil leaking out anywhere. Now I can clean up the mess on the underside of the car. Also, bought those cover new and no baffles came with them..... Thanks everyone for the input!:blob:
 
Yes you need to run a PCV. The breather is desinged to allow air into the crankcase to equalize the pressure drawn by a PCV system via engine vacuum. It cannot sufficiently purge all the crankcase gasses, even in a newly rebuilt engine, therefore it needs to have the gases drawn out by the PCV. The crankcase pressure builds up in the motor & forces it's way out around the valve cover gaskets & possibly the crank seals. It dosen't really matter what valve covers or gasket you're using. Also, as previously mentioned PCV helps with ring seal. Racers actually try to gain negative crankcase pressures by adding vacuum pumps or scavenging systems to their engines for this purpose. I hope this helps.
 
I'm sold on PCV valves, I've now been running a PCV valve for almost two months now. I also replaced the main rear seal that was leaking, may or may not been caused by not running the PCV during break in. The motor did set complete and ready foor install for over a year while I did the rear end swap and front end work. Seal may have dried out and burnt on cam break in???

With the PCV now installed I have no oil leaking from the valve covers, breather. I still have a very slight rear seal leak, maybe a drop per day or two, damn it! It was tough getting the pan back on without the pan radius gaskets tabs pulling out.....maybe too much ATV! The rings have now seated better also, was getting smoke out of the right side when romped on and now appears to be gone. Car seems to be getting great mileage, can't measure yet, speedo is not working. Ordered cable and it showed up with the smaller female connection (didn't measure, maybe 5/8"), wrong, need the 7/8 end.

Thanks again everyone for the input!
 
Here is a simple diagram of a PCV system.

Ted
 

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