[Moedog07]

55twoten I have ran the Mopar style pcv cap successfully on various types of engines. Usually I run an inline PCV valve instead of the 90° elbow. It seems to work well.

 

[MikeB]

From what I understand, the most important job of positive crankcase ventilation is to suck out and burn blow-by gases (some always get past the pistons and rings) to prevent them from contaminating the oil.

However, if you frequently change oil, like in a race car, you don't have to worry so much about oil contamination. In that case, some type of static breather system will work.

 

[Hafrod]

You should use baffled valve covers with a PCV valve or it will suck the oil right into the engine. I thought I had a bad new motor and it ended up being a PCV valve with MT valve covers with no baffle.

 

[nad427]

Green rodder...that's great! well, I like to max the amount of fresh air/fuel mixture in my induction system...as far as I know, oil mist is only good for detonation...if you can make more power out of it I'm all in

Hi Mikko,
Your points are well understood, and you're right about potential detonation, and also there's probably a tiny power loss.
In the OP's post he did mention "for street cars".

I know guys who run PCV's with no breather at all on the street. The theory being that the vacuum pulls the crankcase to at least even if not to a negative pressure. I tried to explain to them that at upper R's the valve closes, but it fell on deaf ears. I got curious though and tried it myself a couple of times. I didn't notice any difference from my usual way so from then on I went back to my valve plus breather, as it also gave me an oil fill by pulling the breather. I like the oil fill on the drivers side myself.

I had a major oil use problem with my 396 that I solved.

fiftyfive210,
I could be wrong but in your first pic it looks like the placement of the PCV hole might be right over a rocker, at speed it would spit oil right up into the valve. In your 2nd and 3rd pic with your 'test' contraption it's obvious that you drilled out the blank cover hole and plugged the first one. That alone might have helped. There's also the possibility that your valve might have stuck open. I had that prob once myself. It took a while for me to find out that mine was only partially closing.

Also, on an unrelated subject (sorry), your intake looks like a Holley Strip Dominator. I really like them things, but I found through experimentation that my 396 ran FAR better on the street with a good dual plane, even an aluminum GM intake worked way better. I was bummed, but couldn't argue with success. I did find however that the Holley did work good on 468 plus motors. If you get bored sometime try a dual plane on your 396 just for kicks.
Dan

 

[topdog]

Don't know of any reason to have a PVC valve or to have a hose connected from a breather to the air cleaner.. Tossed both when I put the 406 engine in , but kept a breather in each valve cover. Breather hose to air cleaner helps if you are pushing a little oil. You must have breathers otherwise there is a strong possibility of oil leakage, engine needs to be vented. The orginal engine has to vent sources 1. the filler cap 2. road draft tube.

 

[JT56]

I have thought using a pvc on one valve cover and the other one using a puke tank with a breather on top. This is a good topic.

 

[fiftyfive210]

Hi Mikko,
Your points are well understood, and you're right about potential detonation, and also there's probably a tiny power loss.
In the OP's post he did mention "for street cars".

I know guys who run PCV's with no breather at all on the street. The theory being that the vacuum pulls the crankcase to at least even if not to a negative pressure. I tried to explain to them that at upper R's the valve closes, but it fell on deaf ears. I got curious though and tried it myself a couple of times. I didn't notice any difference from my usual way so from then on I went back to my valve plus breather, as it also gave me an oil fill by pulling the breather. I like the oil fill on the drivers side myself.



fiftyfive210,
I could be wrong but in your first pic it looks like the placement of the PCV hole might be right over a rocker, at speed it would spit oil right up into the valve. In your 2nd and 3rd pic with your 'test' contraption it's obvious that you drilled out the blank cover hole and plugged the first one. That alone might have helped. There's also the possibility that your valve might have stuck open. I had that prob once myself. It took a while for me to find out that mine was only partially closing.

Also, on an unrelated subject (sorry), your intake looks like a Holley Strip Dominator. I really like them things, but I found through experimentation that my 396 ran FAR better on the street with a good dual plane, even an aluminum GM intake worked way better. I was bummed, but couldn't argue with success. I did find however that the Holley did work good on 468 plus motors. If you get bored sometime try a dual plane on your 396 just for kicks.
Dan

Yes, thanks for the tips! Shortly after I got the car and realized it was using oil I pulled the PCV and saw no baffle. I knew that couldn't be good. Also as you mentioned, the location was bad. The combination of short valve covers and HV oil pump probably swamped the valve. I moved it to the top of the cover to get it away from the oil and I added a baffled rubber grommet. That along with the Mopar oil separator did the trick. It still uses about 1 qt every 1300 miles, but I can live with that.

Regarding the intake, I couldn't agree with you more. I was kind of surprised at the lack of power below 3500 rpm with this engine since this is a pretty stout build. The only thing I can attribute it to is the intake. I had a Strip Dominator on my hot rod (468 BBC) and it ran awesome, but this one is not good at all. I do plan on installing a dual plane. I was looking at the Eddy Performer Air Gap. It doesn't look as cool but I heard that it works well.

 

[1956 Sedan Delivery]

Hi Mikko,
Your points are well understood, and you're right about potential detonation, and also there's probably a tiny power loss.
In the OP's post he did mention "for street cars".

I know guys who run PCV's with no breather at all on the street. The theory being that the vacuum pulls the crankcase to at least even if not to a negative pressure. I tried to explain to them that at upper R's the valve closes, but it fell on deaf ears. I got curious though and tried it myself a couple of times. I didn't notice any difference from my usual way so from then on I went back to my valve plus breather, as it also gave me an oil fill by pulling the breather. I like the oil fill on the drivers side myself.



fiftyfive210,
I could be wrong but in your first pic it looks like the placement of the PCV hole might be right over a rocker, at speed it would spit oil right up into the valve. In your 2nd and 3rd pic with your 'test' contraption it's obvious that you drilled out the blank cover hole and plugged the first one. That alone might have helped. There's also the possibility that your valve might have stuck open. I had that prob once myself. It took a while for me to find out that mine was only partially closing.

Also, on an unrelated subject (sorry), your intake looks like a Holley Strip Dominator. I really like them things, but I found through experimentation that my 396 ran FAR better on the street with a good dual plane, even an aluminum GM intake worked way better. I was bummed, but couldn't argue with success. I did find however that the Holley did work good on 468 plus motors. If you get bored sometime try a dual plane on your 396 just for kicks.
Dan

I agree 396 should have a performer or a weiand strealth could make 30 to 40 hp more on a 396.
In about 1992 I went from a Holley strip dominator to a weiand stealth on a 427 and it made a massive difference I think about 3 or 4 10ths at the drags which is around 30-40 HP.

fiftyfive210 I also agree that the first hole you had the pvc in , in those rocker covers is the one for the breather the second one you used is for a pvc.

Just for the record I use a PVC in my 396 and also my 454 because i have to in Australia.
I dont know if it makes any difference but if my car was race only I would just use breathers and no PVC.

 

[midnightrider]

hmm lots of different ideas on this one...prompted me to research further, here is what I found:

"correct" pcv system set-up requires a fresh air source as well as the pcv valve, to be as far apart as possible so as the air flows between the two it can be mixed with as much of the contaminated internal air as possible. The vacuum source connected to the pcv then pulls air from the fresh air source (the opposing valve cover with either an open breather or a hose connected to the air cleaner), thru the motor and thru the pcv to be routed back into the manifold. From the posts it seems there is much confusion as to when this happens. My understanding is that at high vacuum (idle or cruise) the valve is nearly closed, coinciding with the low amounts of blowby at idle or cruise. As vacuum decreases coinciding with more throttle and thus more blowby, the valve opens then allowing the contaminated air to be routed back into the manifold. At WOT and very low vacuum, the valve is all the way open, but with little or no vacuum the contaminated gasses escape thru the other breather either to the atmosphere or if connected to the air cleaner they are then sucked in thru there.

If I am correct here I think I will make a compromise, here is my logic...I will use a pcv on one cover since I do want some sort of active way to draw contamination thru and out of the crankcase....but I will not attach the opposing breather cover to the air cleaner, and instead just use an open breather there since at WOT when I'm looking for the most power I will not allow the contamination to enter the air cleaner via that route...of course the PCV will be open, but with little or no vacuum I may not be drawing a large amount thru there. (Ha, with the open breather right next to the air cleaner, I may be sucking it in anyway!..but at least it won't be directly routed to it)

I also learned that the various PCV valves are in fact calibrated to close based on an anticipated amount of vacuum...So it looks like the PCV to use for a low vacuum producing cam is from Year One products part # FP1003, used in LT-1 and L-88 vettes back when those motors were making some power. Again if I'm understanding this correctly, this PCV valve will require less vacuum to stay closed or nearly closed at idle and cruise, thus not giving you essentially a large vacuum leak at idle.

Then one more thing I'm wondering about...Assuming you have a pcv system correctly setup... have the carb manufacturers compensated in their mixture settings based on you having a pcv system in place that will always be introducing additional air into the system?...in other words if you remove the pcv and thus remove air, are your factory Holley, Quick Fuel etc carb jetting and bleeds affected?

some weigh ins needed!

 

[Rick_L]

Yes you have the right plan.

I've also recently seen some ads for a "performance" PCV, but the only thing it can do is act similar to the high performance OEM setups you mentioned.

One thing I've never considered was the difference between a breather on the intake side, vs. connecting to the air cleaner. I suppose that at high rpm, with some blow by, you get some oil vapor back into the intake. I'm not sure whether that's a serious deal or not, but I understand the logic.

 

[finn210]

Everything affects to A/F ratios, I would guess that pcv does too...it is like controlled vacuum leak after all. I was amazed how much difference even air cleaner made to mixtures and mine is really free flowing with big element.
Anybody else see the possible problem when running functional pcv that at high rpm low vacuum situation the crankcase ventilation can be very compromised. I would love to see some high performance boat engine crankcase breather systems and how they work.

 

[fiftyfive210]

I will use a pcv on one cover since I do want some sort of active way to draw contamination thru and out of the crankcase....but I will not attach the opposing breather cover to the air cleaner, and instead just use an open breather there since at WOT when I'm looking for the most power I will not allow the contamination to enter the air cleaner via that route...

That's exactly how I have it and it works well for me.

Again if I'm understanding this correctly, this PCV valve will require less vacuum to stay closed or nearly closed at idle and cruise, thus not giving you essentially a large vacuum leak at idle.

I've always wondered why it doesn't act like a big vacuum leak since its connected to what is essentially an open air source.

 

[Rick_L]

I've always wondered why it doesn't act like a big vacuum leak since its connected to what is essentially an open air source.

The reason it's not a big leak is pretty straightforward. The hole that the air passes through in the pcv valve is pretty small. That's why it's "controlled".

 

[nad427]

It becomes apparent that I had my vision of vacuum/no vacuum backwards...oh well. It is observable though, that a running motor with no PCV at car shows will usually show the "wisp" out of the breathers much more than one running the valve, so there must be at least a small amount of draw. The ugly picture of a car pulling in puking vapor out of the draft tube is more than I can appreciate. My internal thought is always.."put a valve on that thing man"!


finn210,
Don't know how they do it now but back in my drag boat days me and my boat buddies just ran usually 2 breathers. On both of my blower motors it seemed to work well.
Also, Smokey Y did a lot of research on air cleaner size and design. If I remember right he found that 14 inch worked good, but also found there was a lot to be gained by the proper shape of the air cleaner base. I wish I could find the article because it seems to me that the numbers he found with right shape were astounding.

 

[finn210]

Dan, the air cleaner I have works like velocity stack...it is circle track style and my engine made more power with it than without.
You wont find me pushing that oil smoke up in the sky...top notch ring seal is the key...I went great lenghts to get that right. Half filled cemented block, "stress" honed cylinders etc.

 

[nad427]

Dan, the air cleaner I have works like velocity stack...it is circle track style and my engine made more power with it than without.
You wont find me pushing that oil smoke up in the sky...top notch ring seal is the key...I went great lenghts to get that right. Half filled cemented block, "stress" honed cylinders etc.

I understand your anality about the seal Mikko. But you gotta admit that there's no way that rings can seal ALL the pressure, no matter how precise. Then there's time and wear to take into account. Running a PCV valve is sorta like putting a bandage on to make an effort to control some of the vapors. There's hardly nothing that makes a motor appear worse than having the "blue wisp" at a car show.

As far as air cleaners go, I'm sure Smokey would have liked to run something like yours, but he had factory GM hood designs to work around. It's amazing what that guy did given the times and what he had to work with. The air cleaner base and top design is just one. What about the anti-common sense approach of intake runners being smaller than head ports to help stop reversion? Or the big one to me is the hot air/fuel motor...that actually worked!!!

 

[hddude]

you talk about air cleaners, how many guys have the usual 14X3 on? i think it`s K&N`s site, but there`s a math problem for the correct size air cleaner. usually, the 14X3`s are to small. my little 355, with the standard 14X3, was choking, according to this. so imagine all those high horse engines, from the factory with 14X3`s, choking!

 

[nad427]

you talk about air cleaners, how many guys have the usual 14X3 on? i think it`s K&N`s site, but there`s a math problem for the correct size air cleaner. usually, the 14X3`s are to small. my little 355, with the standard 14X3, was choking, according to this. so imagine all those high horse engines, from the factory with 14X3`s, choking!

Your point is funny.
It's even funnier imagining the HP Fords and Chryslers getting pulled by "choking"Chevy cars.

As far as K&N goes...they want you to spend way too much for their product, then go run down John Force!!

 

[hddude]

do ya think K&N made up that equation for the proper size air filter? i`m not telling ya that they are right or wrong, and i`m not even sure i saw this on there site. but, i know i saw it somewhere. and, seems to make sense.

 

[hddude]

and, i don`t know what you mean by, being pulled by choking chevy cars.