Crankcase Venting

[Flchallenger]

Have a fresh 512 stroker. Have a pcv on one side with a breather on the other that is not attached to anything. Breather side is blowing small amount of oil out on the valve cover which is dripping on the header. I am thinking I should put a original style breather that plumbs into the air cleaner to provide a vacuum. But I am wondering why not another pcv on the other side and tie them together to the port on the back of the carb. I saw a add for adjustable pcv valve which I have never heard of. And how would you adjust one. How much vacuum should there be. Do you get more vacuum from the carb or the air cleaner. Does it matter? I have the cast aluminum mopar valve covers. On the passenger side it has the cut out for a cap and some of the oil was coming out were the flange holes are on the side. So looked for a larger grommet to cover it and seal it better but couldn't find anything but a pcv valve one. Should I put a regular breather with a oil catch can to the air cleaner? Not sure what to do to be honest. Any ideas on what others have done is appreciated.

 

[NoCar340]

How many miles are on the engine? Some blow-by should be expected for the first several hundred miles until the rings have fully seated. My Valiant has Total Seal zero-gap rings and does the same thing. The engine's only got about two hours' run time on it so I'm not concerned.

 

[Chryco Psycho]

It is a cross flow system , the vacuum is through the PCV to limit the draw , the other side , the breather is where clean air enters the engine , the reason it was connected to the air cleaner was to get cleaner source for the incoming air , if you put a PCV on both sides where can the air enter ?
The other issue is to be sure the covers have the steel baffle plates screwed on under the PCV & breather .
AN original type breather should help with the dripping at least .
I agree that a fresh engine will have more blow by & it will decrease as more miles are driven .

 

[Flchallenger]

It is a fresh motor. 150 miles on it. I thought it would be a cross flow too but I thought if it goes to the air cleaner it would sucking air into the motor it would put a vacuum on it. Never knew this. Oh yes it has the baffles in it. I looked thru the hole to make sure. Thanks. It is amazing the knowledge on this forum.

 

[Flchallenger]

I think I need go and put some miles on it now. Just take a rag and wipe up the mess like a kid with a snotty nose. Once again thanks..

 

[Chryco Psycho]

Drive the wheels off it !!

 

[craigbred]

This is a great question! I have been using the valve cover breathers with the 1/2" hose barb on them, and running the hose under the car and venting it there. My concern was "un-metered" extra air into the intake man. making carb tuning more difficult. I know I know, the factory has been doing it for decades, but with a big cam, carb setup with low intake vacuum is already a challenge. What are you guys doing when using big cams?

 

[Chryco Psycho]

I used 1 way check valves into the exhaust the valve are production in 80 Mopars the exhaust flow will draw out just like a PCV AT high RPM

 

[craigbred]

I tried the check valve method last summer, I really wanted that to work. My brother-in-law and I had just installed a 3 " exhaust system , X crossover, with straight thru Magnaflow 14" 11229 mufflers located next to the gas tank. For a full length system, we tried to make it as free flowing as possible. We angled the PVC draw at about 45 deg, just after the collectors, on a straight section of the exhaust tubing. Even with all this, I connected my most sensitive vacuum gauge to the 1/2" pipe in the exhaust, taped it to the windshield, and got essentially no vacuum or pressure at any RPM while driving. I was hoping for at least 2 or 3 inches of vacuum, but got essentially zero vacuum or pressure. By comparison, with my old 2 1/2" system, more restrictive bends, and more restrictive Flowmaster super 44 mufflers, I had 2 - 3 PSI positive pressure (full throttle, high RPM) with the same measurement technique. I had read somewhere that the exhaust draw method works best with open headers, and my measurements support that.

 

[fasjac]

I think I need go and put some miles on it now. Just take a rag and wipe up the mess like a kid with a snotty nose. Once again thanks..

And get the temp around 195-200

 

[NoCar340]

This is a great question! I have been using the valve cover breathers with the 1/2" hose barb on them, and running the hose under the car and venting it there. My concern was "un-metered" extra air into the intake man. making carb tuning more difficult. I know I know, the factory has been doing it for decades, but with a big cam, carb setup with low intake vacuum is already a challenge. What are you guys doing when using big cams?

Exhaust crankcase evac systems don't work as intended with mufflers or even full straight-pipe exhaust, assuming they ever work at all. Even on open headers, they don't come into play until well above most folk's cruise RPM. There has to be serious gas flow and velocity past those inlet tubes. They're useless on street cars.

The PCV is metered air. That's why it's a weighted, restricted-flow valve instead of an open pipe into the valve cover. It's an engineered solution, not some oh-**** 10-second hatchet job to appease the EPA nor haphazard horsef__kery the janitor devised. Some very smart people were paid very good wages to implement them. There are literally dozens (maybe hundreds?) of PCV valve part numbers, despite there only being a few basic styles.

I have a 340 with an 830 mechanical secondary Holley, a 254°/262° (.050") solid roller cam with .582" lift, and the stock 1969-style PCV/breather arrangement. I've had far more issue getting the carb to run lean enough at idle and cruise. "Unmetered air" through the PCV simply is not an issue.

 

[craigbred]

Exhaust crankcase evac systems don't work as intended with mufflers or even full straight-pipe exhaust, assuming they ever work at all. Even on open headers, they don't come into play until well above most folk's cruise RPM. There has to be serious gas flow and velocity past those inlet tubes. They're useless on street cars.

The PCV is metered air. That's why it's a weighted, restricted-flow valve instead of an open pipe into the valve cover. It's an engineered solution, not some oh-**** 10-second hatchet job to appease the EPA nor haphazard horsef__kery the janitor devised. Some very smart people were paid very good wages to implement them. There are literally dozens (maybe hundreds?) of PCV valve part numbers, despite there only being a few basic styles.

I have a 340 with an 830 mechanical secondary Holley, a 254°/262° (.050") solid roller cam with .582" lift, and the stock 1969-style PCV/breather arrangement. I've had far more issue getting the carb to run lean enough at idle and cruise. "Unmetered air" through the PCV simply is not an issue.

Thanks for the tips on PCVs NoCar340, you gave me some inspiration to play around with that someday. I have a similar size cam, 247/251 (.050"), 112 sep., .560" lift hyd. roller, with a 505, so I might be able to get a PCV to work ok (though the hoses under the car work ok too).

I'm running a 870 vac. secondary Holley. I finally got the carb pretty good a idle and cruise. In the beginning, I was a little rich at light throttle cruise too. I installed brass set screws in the low speed jet/hole drilled in the metering block, and then drilled the set screws to a smaller hole than the original hole. With that, I "jetted down" until it was too lean and it would "lean surge" at 20-30mph, then richened back up from there. But I'm having trouble eliminating the momentary lean hesitation when the secondaries open, even after slowing them down AND adding a stronger spring. My next guess is vastly smaller secondary air bleeds and/or bigger sec. pilot jets to try and richen up the mixture as the plates swing past the slot.

Oh the fun of trying to make a Holley run like fuel injection...