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!

[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/...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.

[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.

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?