What you running...PCV...breather...?

What you running...PCV...breather...?

Postby Mr_Bowtie [OP] » March 15th 2015, 3:22am

Currently running just a breather on the driver's side and thinking that the motor might benefit from adding a PCV valve on the driver's side and put my breather at the end of my fill tube that is coming off the passenger's side valve cover. Or get new covers with more ports in them. My current breather is filthy and full of oil.

So, what is everyone running? Options? Suggestions?

Also my 350 is carb'd.

Thanks, Nick
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Re: What you running...PCV...breather...?

Postby Mmusicman » March 15th 2015, 12:43pm

My PCV valve in on my passenger side cover, and the breather is on the stock oil fill tube on the DS. Sounds similar to what you want to do.

One thing for certain.. and PCV valve is an essential part of the system. It draws cylinder blow-by gases from the crank case and the vacuum helps to prevent seals and gaskets blowouts and oil leaks. Negative crankcase pressure may be good for a little free extra economy and horsepower too.

You can see my PCV valve on left side behind alternator.. and breather on top right:
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Re: What you running...PCV...breather...?

Postby Mr_Bowtie [OP] » March 15th 2015, 2:09pm

Thanks for the feedback......I am gonna definitely set mine up like that. My engine compartment is dirty(crap coming out of breather I think) and the motor has moisture on the dipstick so seems like it's not breathing/venting enough. It's also that time of the year too I guess with weather changing.
The breather with tube back into the carb would prolly be a nice addition too. Hopefully I got some ports open on my carb....

I was also thinking previous owner might have the breather on a valve cover without a baffle too....I gotta check that out.

Beautiful motor you got there Mmusicman!!! :rockon:
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Re: What you running...PCV...breather...?

Postby WoodButcher » March 15th 2015, 2:27pm

Mine is a TBI with the passenger side PCV vented to the inside of the air cleaner. The drivers side also has a vent piped into the throttle body but it has no flapper or filter. My pics show the chromed caps but I kept this setup same as stock. The drivers side was just a rubber / plastic tube originally.
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Re: What you running...PCV...breather...?

Postby Mr_Bowtie [OP] » March 15th 2015, 2:38pm

Glad I asked cause my setup is not doing the motor any good....thanks guys!
I got a list of stuff I wanna get done on this thing. :rockon:
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Re: What you running...PCV...breather...?

Postby Mmusicman » March 15th 2015, 3:27pm

Mr_Bowtie wrote:The breather with tube back into the carb would prolly be a nice addition too. Hopefully I got some ports open on my carb....

There should be two large vacuum ports at the base of the carb (one front and one rear). I would expect the front port is going to the brakes vacuum booster... mine is. The rear port on the carb is there for the PCV. If however it is being used already, there should be an available vacuum port on the manifold (probably a hex plug). This is where I'm getting my PVC vacuum from (rather than from the back of the carb). This manifold vacuum port is located directly behind the carb.

I wanted to use the breather in the air filter for the return.. but there was no way to do this AND have the oil filler tube in the opening on the DS valve cover. So I used a breather in the fill tube as was intended with this breather. Note: these cheap Spretre valve covers have internal baffles.

Mr_Bowtie wrote:Beautiful motor you got there Mmusicman!!! :rockon:

Thanks.. I kept is simple and clean. It's a joy to have! Real easy to work on too!

In this photo you can see where I have the PCV attached to manifold (braided line)

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Re: What you running...PCV...breather...?

Postby Mr_Bowtie [OP] » March 15th 2015, 6:58pm

Okay cool!!
I will check out my intake cause my vacuum ports are being used. Brakes are on the rear of the carb and the other vacuum port splits to two smaller lines. Probably for some accessories I have to investigate further.

I have nice valve covers the hole where my breather is does have a baffle so I will put the PCV there going to a vacuum source. Then get a breather that will fit snug in my oil fill tube..or modify the oil cap to hold one tight...cause there is a lot shaking under that hood.. :rockon:
Last edited by Mr_Bowtie on March 15th 2015, 7:18pm, edited 1 time in total.
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Re: What you running...PCV...breather...?

Postby Mmusicman » March 15th 2015, 7:03pm

Mr_Bowtie wrote:Then get a breather that will fit snug in my oil fill tube..

The standard valve cover breathers will fit the tube.. including the rubber grommet.
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Re: What you running...PCV...breather...?

Postby Mr_Bowtie [OP] » March 15th 2015, 7:20pm

Okay...that makes it easy.
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Re: What you running...PCV...breather...?

Postby Lumpy » March 15th 2015, 7:27pm

I'm not entirely sure if I know how the air flows in a PCV system.

On my stock V6, the valve side (passenger side) runs to a large vacuum port on the front of the TBI. The non valve side vent (driver side) goes to a nipple on the air cleaner spacer. That air cleaner spot is constantly oily and gunky.

On the "passive" side (the non-valve side) is the air going IN to the valve cover or coming OUT of the valve cover?


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Re: What you running...PCV...breather...?

Postby Mmusicman » March 15th 2015, 7:51pm

Lumpy wrote:On the "passive" side (the non-valve side) is the air going IN to the valve cover or coming OUT of the valve cover?

Well that's a good question! Ideally, it should go in on the passive side. It may however, go either or both ways.. depending on idle, cruise, or acceleration (during a lack of strong PCV vacuum). Other possibilities include a PCV valve that is not working properly, that is could cause blow-by out the passive side... since crankcase pressure is exceeding what the pcv valve is pulling. A worn engine may also produce MORE blow-by than what the PCV system is designed to pull.

Image

Typically, air is drawn in though the air filter, then enters into the passive side, pulls thru the crankcase, and back out the PVC side. This is called a "closed system". "Aftermarket breathers" (open systems) work similarly, passing fresh air into the passive side as well. Older stock systems with a filter screen inside the air cleaner but outside the filament would be an older form of hybrid (open and closed), since excessive reverse flowing gases would still be most likely drawn into the air filter.

The passive side breather inside the air cleaner may actually serve a dual purpose.. since it is now part of a closed system. If blow-by exceeds what can be pulled thru the PCV valve, then it would be forced out the passive side as well. Since vacuum exists here too (especially under hard acceleration) gases would still be pulled from crankcase back into the combustion chamber (in this case thru the carb) from either passive or PCV side.

The objective of the PCV system is not only to "breathe" air through the crankcase.. but rather keep the crankcase under a vacuum condition. While idling or low rpms.. air goes in through the "passive" side (due to strong PCV vacuum). But under hard acceleration there is a minimal vacuum on BOTH sides... less at the PCV valve and perhaps more at the passive air cleaner side. If pressure in the crankcase builds faster than the PCV valve can remove it.. then it will be expelled thru the passive side. In the case of closed stock system, gases and pressure will simply exit and be drawn into the carb inside the air filter.

Having vacuum (on either side) during hard acceleration would probably be most beneficial, due to pressure from hard blow-by. The aftermarket breather may actually be a compromise (open system).. but is still a good one. We know you certainly don't want positive pressure in the crankcase under any conditions. Vacuum in the crankcase may be essential.. but drawing out fumes and spent gases is critical to reducing sludge build-up and oil contamination.

The PCV valve, besides blocking backfires, will actually meter the amount of air it pulls. Idling and low rpm produce strong vacuum.. pulling hard on the PCV valve. It has a tapered pintle which reduces some of the flow caused by the strong vacuum. If this didn't happen, you would run extremely lean at idle, causing a poor running/idling condition. Under cruise speed or stronger acceleration, the vacuum draw on the PCV valve is less.. raising the valve to a more open condition.. causing easier flow. Either way.. the flow (and vacuum to crankcase) is metered.

My breather actually has a slight restriction in it, which I believe is somewhat beneficial in helping to maintain negative crankcase pressure or vacuum. I'm sure there is plenty of good reading on this.
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Re: What you running...PCV...breather...?

Postby Mr_Bowtie [OP] » June 4th 2015, 10:42am

Thanks for the help guys.....got my PCV all hooked up. Breather fits perfect in oil tube like ya said. My oil will hopefully stay cleaner now!!! :rockon:
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