Pcv or not to pcv?

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fast68chevy

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Rick and Bruce are correct, there is PCV on non road draft tube motors for a big reason. your motor oil and bearings and etc will suffer without propert ventilation throughout the crankcase. you have to be able to remove the moisture from inside the crankcase or you will have sludgy and acidic oil and damage to internals over time. manifold vacuum 3/8" in one V/C and filtered return in the other. unless it is an old school road draft tube before 1968 or so motor. but iif you wanna be "smart" and run no proper working pcv and have moistureized oil and sludge and acids in your crankcase. then well, its your motor.. good luck lol
 

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The only drawback I've heard of on a PCV system (and why some people disable it) is because sometimes you can get oil in the PCV system. This only tends to be an issue on newer vehicles, especially with direction injection. If the PCV is connected to the intake before where the gasoline is introduced it can foul up components of the intake. Some people install an oil catch can or disable the PCV entirely. The oil being recirculated through the PCV system can foul the intake valves, but with carbureted, TBI and port injection systems gasoline still passes over the intake valves and cleans them. This doesn't happen with new direct injection systems. I don't feel bypassing the PCV system or installing a catch can is necessary on these older vehicles.

On GDI engines, you have to use Top Tier gas as well as frequently clean the intake side of the head. The top tier gas has additives to help keep it clean. On my Turbo HHR, I have pulled the intake 2-3 x to clean it. Now, I run Top Tier gas and use GDI cleaner every 5-10k miles. The car makes 330hp out of a 2.0 which is amazing but a lot of upkeep. The newer systems, I believe, added an injector in the intake to wash the valves which should have resolved the issue.
 

dsteelejr

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The newer systems, I believe, added an injector in the intake to wash the valves which should have resolved the issue.

I’ve heard that the engineers caught on to what was happening there and newer GDI models have both port and direct injection and it will alternate between the two depending on driving conditions to keep those valves clean.
 

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I run breather on passenger side and pcv on the drivers side valve cover.

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SirRobyn0

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I'm going to preface this by saying I did not read though all of the posts. I've made a career out of being an auto mechanic and I'd hardly say I know everything, but I want you to know that this response comes from those years of experience, and understanding. Yes there was a time automobiles ran nothing more than a breather, but there was also a time when most engines were shot in less than 100K. I'm not saying it's all to do with the PCV I'd say hardly, but they did play a roll. You NEED to have a PCV valve in one valve cover and some sort of a breather in the other. The breather can either be the direct type or hose to air cleaner doesn't matter.

Two reason you HAVE to have a PCV valve. #1. It helps to suck moisture and other contaminants out of the engine. Moisture and other contaminants gets in there from everywhere, from the air that comes in the breather to stuff that gets by the rings. You start the truck and it warms up, without a PCV most of that is just going to get churned around inside the engine and get more contaminated with some of it possibly getting out the breather. Shut it off and let it cool and that crap settles in the oil! With a PCV at idle and part throttle, the PCV valve will pull some suction into the engine and the breather will let in some fresh clean filtered air to circulate out the old contaminated air and bring in fresh.

#2. I have seen vehicles with mild to moderate oil leaks or burning solved by replacing a clogged non-functioning PCV valve. I'm not saying that an engine will or won't use oil without a PCV I'm just saying I've seen some leakage solved with a new PVC valve. Food for thought anyway.
 
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Frankenchevy

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Your carburetor wants that vapor.
I doubt it will ever tune correctly with that port plugged.
Huge difference between the driver side and passenger side cylinder head...damn. One blows and one sucks yes?

Yes.

* I dont know anything about big blocks though...

In my my mind the issue still isn’t solved.

I will say I did a fair amount research online when I was setting up my system.

I found way more engine pros recommend a PCV valve.And just like Shorty noted on the passenger side.

I think you’re on your own here.Good luck!

Dang, I didn’t think it mattered. I thought the vacuum of the intake created vacuum in the crank case either way—so long as you have a breather on the opposite side to allow the air to flow through.

So what say the experts who have an actual reason to one side or the other, does it make a difference?

My mind is blown, lol
 

Rusty Nail

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They got experts in here? Dang! I didn't know...unless you're talkin about Bucket...he seems to know a bunch of stuff. Or maybe Bruce knows..or Rick maybe?
What about Robyn?

I feel like this may be a trick.

It's not gonna change a damn thing if it is.

Looking at a SBC V8 from the front, the crankshaft rotates clockwise. It weighs a bunch and has big assed weights hanging off of it, yes? Yes. Displaces a lot of volume inside the crankcase and it spins. - It moves a lot of air that must have somewhere to go.

As it spins up the passenger side, those weights are pushing air. As it spins down the driver side, those weights are pulling air. Into and out of the engine for example's sake. Read this as ring seal.
Ring seal contains the horsepower made in the combustion chamber. Keeps it and contaminate (blowby) from entering the wet sump oiling system. This is both the why and how there is a PCV on one side (driver) and a breather on the other (passenger)

Rather or not that is true, that is how I think of it. Do a simple test for yourself.

Put a pcv in both valve covers , tell US what happens.
Conversely put a breather in both valve covers and tell us what happens.

PCV valves make horsepower because they - improve ring seal and reduce blowby.. They introduce vacuum into the crankcase improving ring seal. Dry sump oiling makes more power creating more crankcase vacuum than a wet sump.
Ever wondered why some drag racers for example utilize vacuum pumps? They are sold in Jeg's or at Summit...INDY cars operate under negative crankcase pressure in example..there's no breathers - it's all sealed.

Look I don't know much about it but I think it's cool you asked me. Thanks. I'm certainly no expert and any number of those dudes prolly knows better than I. Maybe you'll get some other help later.:shrug:
 
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SirRobyn0

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In my my mind the issue still isn’t solved.

I will say I did a fair amount research online when I was setting up my system.

I found way more engine pros recommend a PCV valve.And just like Shorty noted on the passenger side.

I think you’re on your own here.Good luck!

I can't image there would be a difference in passenger or drivers side PCV location. Unless there is a difference in the baffling or hole size on the valve covers side to side, which might vary depending on if factory or aftermarket covers are in use. I'd like to know the reasoning on that as well.

Personally I would not have engine work performed by any builder who recommends not running a PCV, I guess maybe the one scenario I could see where no PCV would actually be valid is in an engine with so much overlap that little vacuum is created such as a race motor, but in that scenario longevity of the engine doesn't matter.

Dang, I didn’t think it mattered. I thought the vacuum of the intake created vacuum in the crank case either way—so long as you have a breather on the opposite side to allow the air to flow through.

So what say the experts who have an actual reason to one side or the other, does it make a difference?

My mind is blown, lol

Just as an FYI, on the PCV location thing, my 1984 C-20 305 with factory valve covers has the PCV in the drivers side and breather in the passenger side. This is factory as confirmed by the vac diagram under the hood. Not sure if it is for all years, engine sizes ect.
 

Frankenchevy

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They got experts in here? Dang! I didn't know...unless you're talkin about Bucket...he seems to know a bunch of stuff. :shrug:
Yep, that’s the guy!
 

Michael Benardo

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I can't image there would be a difference in passenger or drivers side PCV location. Unless there is a difference in the baffling or hole size on the valve covers side to side, which might vary depending on if factory or aftermarket covers are in use. I'd like to know the reasoning on that as well.

Personally I would not have engine work performed by any builder who recommends not running a PCV, I guess maybe the one scenario I could see where no PCV would actually be valid is in an engine with so much overlap that little vacuum is created such as a race motor, but in that scenario longevity of the engine doesn't matter.



Just as an FYI, on the PCV location thing, my 1984 C-20 305 with factory valve covers has the PCV in the drivers side and breather in the passenger side. This is factory as confirmed by the vac diagram under the hood. Not sure if it is for all years, engine sizes ect.
 

Michael Benardo

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The crankshaft spins clock-wise, so a slight vacuum will be generated on the driver's side and pressure on the opposite side. If you put the PCV in the driver's side and the breather on the opposite side, you are working against that fact, so I would put the PCV on the passenger side, unless you have a diagram that shows otherwise.
 

Turbo4whl

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Sure are a lot of posts in this thread to reach a simple answer to @82sbshortbed 's question. Again, I will say yes.

Don't know if I qualify as an expert, but I know I am a professional as they have been paying me for almost 50 years to fix trucks. So I'll tell a story:

Back in the mid 1960's before the PCV became mandatory, GM experimented with the 305 V6 engine, found in only GMC trucks. This engine has 2 PCV valves, one threaded in each head. The breather was on the oil fill tube located in the intake manifold, going right to the engine valley.

Part of the standard tune-up was to remove both valve covers and replace the 2 PCV valves. Fit new valve cover gaskets and install.

I am going to guess (no expert) that this system did not work as well as GM had planned since I don't recall other engines plumbed this way.
 

SirRobyn0

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The crankshaft spins clock-wise, so a slight vacuum will be generated on the driver's side and pressure on the opposite side. If you put the PCV in the driver's side and the breather on the opposite side, you are working against that fact, so I would put the PCV on the passenger side, unless you have a diagram that shows otherwise.
That does make sense. As stated before, my diagram indicates drivers side for PCV.It's good to know the theory at least.
 
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Rusty Nail

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