Crankcase ventilation

[speED]

I read various threads, there seems to be many opinions on how to provide crankcase ventilation. Some members have claimed that you should always run a PCV valve, engine will last longer and there is no negative effects. I like the idea of the engine lasting longer but here is my dilema. When I run filtered air on 1 valve cover and a PCV valve on the other attached to vacuum port on backside of carb cylinders 5,6,7, & 8 on my BBC become considerably/ dangerously leaner than Cylinders 1,2,3, & 4. Remove the PCV and all cylinders look exactly the same. Has anyone ever ran into this situation and found a solution.

[camrat68]

Are you saying that the bank with the PCV with cylinders 2,4,6,8 come up leaner than the breather equipped bank with cylinders 1,3,5,7? How are you determining this?

Have the heads been ported and were they checked for porosity?
Have you done a leak down test?
How old is the valve job?
What fuel injection system are you running?
What fuel are you running?

Jim

[TheJDMan]

I think he is saying the back half of his engine goes lean 5,6,7,8. OP, Are you running a dual plane or open plenum intake manifold? Also, is the PCV valve in good condition and not stuck open?

[speED]

Correct, back half of engine goes lean. Open plenum manifold. Yes, PCV is in good condition. I would really like to get this to work, I also get less gas fumes/ oil smell when PCV is hooked up. Was actually thinking of drilling and tapping for 2 fittings directly below the carb into both sides of intake manifold and using that for vacuum. I would hate to do this and find out it didn't work.

[TheJDMan]

Does your intake have a 1/4"NPT plug in the rear below the carb base? Some do and some don't. If yours does try moving the PCV vacuum hose to that location and plug the carb fitting. If not you might consider drilling and tapping one on the back side of the plenum. See if that helps. You could also try opening the secondary butterflys and then readjusting the primary idle screw.

[speED]

My intake does not provide a port. Why do you feel a port in the back of the intake would be any different than the port currently in the back of the carb? I feel if the port continues to favor the rear of the engine the rear cylinders would still be lean.

[speED]

As I do more research, I'm starting to wonder if my valve just has to much airflow, meaning do I need a different part# for the valve. My engine is basicaly a drag race engine in a street car. Engine is a 460 cu. in. BBC, single plane manifold with 950 cfm carb. I purchased a valve for a BBC. If a put an manometer gauge on the PCV hose I do not even know what would be an acceptable reading.

[Yelcamino]

Have you tried moving the PCV from the carb to the air cleaner base?

[speED]

Have you tried moving the PCV from the carb to the air cleaner base?

No, since vacuum is not always the same on both sides of the throttle plate. I dont see how that would work correctly.

[Yelcamino]

No, since vacuum is not always the same on both sides of the throttle plate. I dont see how that would work correctly.

Are you running a closed PCV system (one valve cover vented to the air cleaner and the other to the carb base via the PCV valve)? If you are, then connecting the PCV to the air cleaner base won't do anything.

If you're running one valve cover with a breather venting to the atmosphere, then moving the PCV to the air cleaner base so it only works when the throttle blades open "may" help your lean condition. I don't know for sure, just putting an idea on the wall.

[speED]

Are you running a closed PCV system (one valve cover vented to the air cleaner and the other to the carb base via the PCV valve)? If you are, then connecting the PCV to the air cleaner base won't do anything.

If you're running one valve cover with a breather venting to the atmosphere, then moving the PCV to the air cleaner base so it only works when the throttle blades open "may" help your lean condition. I don't know for sure, just putting an idea on the wall.

Yes, I was trying to run a closed system. I actually tried what you said without the PCV valve and that works fine, was hoping to make it fully closed system to eliminate all smells. Wife is sensitive to the smell thing with the older cars.

[Yelcamino]

Wife is sensitive to the smell thing with the older cars.

Same with mine, which is why the old cars are in a different garage! :twothumbs

[sam 74]

have you considered an evac system? i run one with full exhaust on the street, but you need to make sure your exhaust system is up to par fot the job.

[speED]

have you considered an evac system? i run one with full exhaust on the street, but you need to make sure your exhaust system is up to par fot the job.

Have not looked into that, what do you mean by exhaust system has to be up to par for the job?

[mmosley]

Have not looked into that, what do you mean by exhaust system has to be up to par for the job?

I think he is referring to the style that pulls a vacuum on the valve covers via hose to the header using the venture effect. I consider that pretty much a race only item. I would be more inclined to look into using a vacuum pump that pushes to a recover tank with a breather.

My intake has a port for the PVC on the bottom directly in the center. I have been contemplating what I would do for mine, the standard breather in one cover, valve in the other drips oil under g loading, have been considering doing a cross over system similar to a circle track car.

http://www.forabodiesonly.com/mopar/attachment.php?attachmentid=247285&stc=1&d=1310586319

[speED]

[QUOTE=mmosley;1095976]I think he is referring to the style that pulls a vacuum on the valve covers via hose to the header using the venture effect.

That is what I thought but I figured maybe there was something I did not know.

The vacuum pump I have been tossing around, not to excited about adding another component to the engine compartment.

You have inspired me to post another thread in reference to a vacuum pump.

Thanks,
ED

[fun2run]

Oil introduced into the combustion chamber with fuel is known to have a vast reduction to octane or stoich values of fuel. I would think you are seeing the result of that on the plugs. Think of all the OEM forced induction platforms where aftermarket always introduce a oil catch can system. Or furthermore a LS platform with the same catch can. Why remove an emissions loop on a LS platform and plumb to a catch can? Lowers performance ie: Octane. Run a catch can system and problem solved.

https://static1.pt-content.com/images/pt/2014/10/IMG_1672_zpsfa813107-1.jpg

[parsonsj]

I'm also not a fan of the vacuum pump... though it will (if combined with a fresh clean air source on the valve cover) help evacuate the acidic air in the crankcase and give the benefits of a real PCV. But where would the output of the vacuum pump go? To the atmosphere? That's not going to keep the fumes down either in the garage, or while driving.

I think we need more information. Are you getting excessive blow-by? Perhaps enough air is coming through the PCV that you're leaning out the back cylinders (which you already know, I think). It might be worth putting a vacuum gauge on the line coming from the PCV to the carb to see if you are getting vacuum or positive pressure there, especially at part throttle and idle.

[speED]

I think we need more information. Are you getting excessive blow-by? Perhaps enough air is coming through the PCV that you're leaning out the back cylinders (which you already know, I think). It might be worth putting a vacuum gauge on the line coming from the PCV to the carb to see if you are getting vacuum or positive pressure there, especially at part throttle and idle.

Forcast is ran the next day or two, but I'll put a vacuum gauge on and let you know. Yes, the pcv is the cause of the lean condition. I do not believe I have excess blow by. I'm pretty sure all my problems are occurring as i go down the highway. At 55mph, I spin 2800 rpm - with very little throttle I think the vacuum is too much for the pcv valve.

[speED]

Run a catch can system and problem solved.

https://static1.pt-content.com/images/pt/2014/10/IMG_1672_zpsfa813107-1.jpg

Engine compartment looks awesome. Shafiroff is not too far from my home. How does your catch can drain back into the engine, fitting on side of oil pan?

[fun2run]

Engine compartment looks awesome. Shafiroff is not too far from my home. How does your catch can drain back into the engine, fitting on side of oil pan?

It does but it is not mine. Most just have drains at the bottom of the cylinder.

[speED]

Progress update:

I placed a vacuum gauage on vacuum hose from pcv to manifold vacuum - vacuum is present.

I borrowed a pcv valve for a LS engine, part #12572717, this is the replacement valve GM supplies which removes the actual valve and has only a small hole in it. Lean condition disappeared and no more smells. The only thing I need to watch is oil consumption - I will not be able to use my previous baffled grommet with this valve.

[parsonsj]

Cool! A catch can is definitely something you'll want to keep oil from being burned through your now-working PCV system.

I've had good luck with several, with a modified Mann-Hummel ProVent being my current choice. Mike Norris makes a nice setup too. Having the catch can drain back into your pan will make the whole system maintenance free.

[speED]

I've had good luck with several, with a modified Mann-Hummel ProVent being my current choice. Mike Norris makes a nice setup too. Having the catch can drain back into your pan will make the whole system maintenance free.

Did you determine the ProVent size based off of their chart. Based on my horsepower I would need the ProVent 400, I feel like that is huge.

Cant seem to find dimensions for the Mike Norris brand, anyone know how big it is?

[yellow1098Greg]

Simple question for you guys....I have the butler performance valve covers on my pontiac 400 with a fitting built in for a catch can or vacuum pump. If I run just one hose off that fitting to a catch can what will be the function of the that setup? Will it just catch any access oil that tries to get pushed out of the engine when the pressure gets high? I don't have any access blow by, but I do have a tiny bit of oil that drips from the breather after some really spirited driving. Thanks as always!

[TheJDMan]

A single hose from your valve cover to a catch can will be of little benefit by it's self. First off you need a catch can with two ports and internal baffles then to install a complete PCV system you need the hose from the valve cover to the catch can and a second hose from the second port on the catch can to a vacuum source either on the engine or a vacuum pump. Then on the opposite valve cover you need to install an air filter of some sort to allow clean air to enter the system. The whole point is to have some amount of air flow through the engine crankcase to vent the oil mist and gasses out to the catch can.

[yellow1098Greg]

Makes sense...thanks for the explanation. I have a pontiac 400 and the PVC runs from the front on the intake up to the carb.so I was trying to figure out how incorporating a catch can to that setup would be helpful. Thanks again!

[dontlifttoshift]

PCV valve should be hooked to the FRONT of the carb if available, you know, the primary side. The rear port is for a brake booster.

[yellow1098Greg]

Yes that is how my PVC is set up to the front of the carb