Breathers and PCV valves

Andy CobraII · Sep 17, 2004

Gentleman,
Just got a nice set of cobra valve covers and was
wondering the best way to install. One of them has
about a 1.5" breather tube on it, while other is flush.

My original setup has a hose going from drivers side valve
cover under carb to intake. The passenger side had a cap
on it with a 2" hose connected to nothing. It had an aftermarket
open airfilter. I now have an OEM airfilter.

Do I install the valve cover with no tube onto the driver side
and run that into the intake, then install the cover with a breather
tube on passenger side and put a hose to the air cleaner? I assume
the PCV valve is in line to the intake, right?

Any help on an effective, emissions legal setup would be appreciated.
If you have a pic of your engine that would probably tell the story.

thanks
andy

Wart · Sep 17, 2004

Andy CobraII said:
Gentleman,

Any help on an effective, emissions legal setup would be appreciated.
If you have a pic of your engine that would probably tell the story.

thanks
andy

I'm assuming a V8?

The oil fill cap on the left bank has the PVC valve. IIRC the factory had a metal tube between two coupling hoses, one coupling hose at the carb spacer, the other hose ont he valve in the valve cover cap.

The tube/ hose on the right bank went to an air strainer/ filter located in the main filter pan. That this hose has been open means you have been sucking unfiltered dirty air into the right banks rockers. may/ may not cause you problems with wear.

I have all these parts kicking around here ....... somewhere.

If you're going to use the PVC there needs to be a filter on the banks cover oposite the PVC. Elsewise your going to suck dirt into the engine. The filter doesn't have to be in the main filter pan, it can be a mini filter on the cover or on the end of the hose.

If your not going to run a PVC (contrary to your intent, I know) you'll still need a breather such as found on old engines. These breathers are filled with a coarse metal mesh that's suppose to catch the oil mist in the blow by that's going through the breather. It's a nice thought. Ever wonder why the right side engine compartment was relitively rust free?

Blue Thunder · Sep 17, 2004

I drew up a typical PCV system in paintshop awhile ago, and still have it on my site.

That 70 Car · Sep 17, 2004

Thanks

A similar diagram came with the covers. Wondered if the II's
had anything strange/different. It looks like if I follow a standard
clean-air in one side, and fumes burnt at intake I should be alright.

thanks for the help.

andy

ps. sorry, yes I was speaking of a v-8 car.

zwhitr · Sep 20, 2004

Blue Thunder said:
I drew up a typical PCV system in paintshop awhile ago, and still have it on my site.

Don't mean to be critical but isn't the flow going in the wrong direction out of the air cleaner??

77sleeper · Sep 20, 2004

zwhitr said:
Don't mean to be critical but isn't the flow going in the wrong direction out of the air cleaner??

nope otherwise you would vacuum pack the engine

Wart · Sep 20, 2004

You don't want to "T" the booster inline with the PVC.

Blue Thunder · Sep 21, 2004

zwhitr said:
Don't mean to be critical but isn't the flow going in the wrong direction out of the air cleaner??

No, the air filter should have virtually no vaccuum signal at all. (unless it's hideously dirty) It's merely acting to clean the air being sucked into the motor from the opposite side.

Blue Thunder · Sep 21, 2004

Wart said:
You don't want to "T" the booster inline with the PVC.

Why not? Are you afraid of accumulating oil in the booster?

Wart · Sep 21, 2004

Blue Thunder said:
Why not? Are you afraid of accumulating oil in the booster?

No.

I would rather have full manifold vac applied to the booster.

I also like having a dedicated source for the booster.

Something about having my booster getting it's vacuum in a blead air circuit. Especially since the bled air is controled by a cheap valve. How much vac will that valve allow to be created anyway? Probably enough to work the brakes long as the engines running.

Finally, it's poor form.

If it works for someone else good for them. Hope they have strong legs.

Ricky D · Sep 22, 2004

I agree , it makes sense....I have a separate line for the booster but never realized in case of failiure...you might end up with an open vac line

Since we are talking about vaccum and pvc.... I always wondered If when you have a Cam with a kinda loopey idle...it might cause a problem with the correct fuction of the pvc?

I have a B cam,it has low vaccum at idle,besides having trouble with carb adjustments...because I have not enough vac...I correct the situation by opening the throtle plates a bit ,but I end up in the transition circuit.... and even with the cam on the shooter adjusted,I still get a lean condition when I nail it,It is short but give a light stumble,somebody told me to drill hooles in the butterflys on the primary to compensate for the low vac to give it more air and then I could back off on the throtle to get a satisfactory idle without ending up in the transition slot... what do you think?

And I noticed that my pvc doesn`t seal right..it rattles,I changed it for a new one with the same result.Is there a way to get a PCV that would work better with less vaccum or should I just get rid of it....emissions is not a problem in quebec What do you guys do?

TheEvII · Sep 22, 2004

First off. I agree that it's not a great idea to have your booster vacuum sharing a vacuum source with anything else.

I have a B cam,it has low vaccum at idle,besides having trouble with carb adjustments...because I have not enough vac...I correct the situation by opening the throtle plates a bit ,but I end up in the transition circuit.... and even with the cam on the shooter adjusted,I still get a lean condition when I nail it,It is short but give a light stumble,somebody told me to drill hooles in the butterflys on the primary to compensate for the low vac to give it more air and then I could back off on the throtle to get a satisfactory idle without ending up in the transition slot... what do you think?

I have a 750 Edalbrock and I drilled holes in the butterflies in order to get a leaner idle and make carb adjustment easier but this won't help your bog. Bottom line is you're probably still running lean and you should jet up the carb if you'd like to get rid of the lean condition. After that you can decide if you should drill holes in the butterflies because once you do that, there's no reversing it.

As far s the vacuum goes, some people run a vacuum reserve but I don't think that will help your PCV situation.

Ricky D · Sep 22, 2004

TheEvII said:
First off. I agree that it's not a great idea to have your booster vacuum sharing a vacuum source with anything else.

I have a 750 Edalbrock and I drilled holes in the butterflies in order to get a leaner idle and make carb adjustment easier but this won't help your bog. Bottom line is you're probably still running lean and you should jet up the carb if you'd like to get rid of the lean condition. After that you can decide if you should drill holes in the butterflies because once you do that, there's no reversing it.

As far s the vacuum goes, some people run a vacuum reserve but I don't think that will help your PCV situation.

I get a lean spot but then I run at 12 :1 afterwards,I have a K&N af meter in the car... I run rich at full throtle and idle is fine because I leaned it with the idle mixture screws,but I think that since I `m in the transition slot,it might mess up my adjustments.Off idle,the adjustment screws have no effect ?Right,And there is no air blead adjustments on Holley 4150 as far as I know,so like you said I should change the jetting,but I suspect my stumble because my transition circuit is ineffective.

I have a 6.5 powere valve...that too is a problem...I wanted to put a 4.5 because my vaccum signal is weak.

I think i`ll pay a carburator expert to Dyno tune the car,it seems like i`m runing in circles right now....I`ll watch...I see that alternative like a carb 101 course....

The car still runs great but I know it`s not as crisp as it should be when I floor it

welder4956 · Sep 22, 2004

The hose from my PCV valve runs from the right valve cover to the connection on the base of the carb and the filler cap has a built in filter. The brake booster is connected to the manifold vacuum tee on the back of the intake. If you route the hoses that way, there should be no issues with sufficient vacuum for the brake booster.

77sleeper · Sep 22, 2004

only girls need vacuum brakes

welder4956 · Sep 22, 2004

76_Cobra_II · Sep 22, 2004

Blue Thunder said:
I drew up a typical PCV system in paintshop awhile ago, and still have it on my site.

Mine doesnt look like this at all.... Mine has the push in filter on both sides. Is that bad? I bought it that way and I dont know any better if its wrong. I have a 4B Edelbrock carb and manifold. Aftermarket open air cleaner that is like 8" around. I do notice that it doesnt take long for steam/smoke to be seen coming from the push in filter caps. LET ME KNOW! OH, and when Istep on the brake pedal, I can hear my engine rev up just a little bit every time. Maybe just enough to be a 1/2 to a full RPM. Is that bad?

77sleeper · Sep 22, 2004

76_Cobra_II said:
Mine has the push in filter on both sides. Is that bad?

they will smoke under certain circumstances and can spill oil at high RPM for sustained periods

77sleeper · Sep 22, 2004

76_Cobra_II said:
Mine has the push in filter on both sides. Is that bad?

they will smoke under certain circumstances and can spill oil at high RPM for sustained periods

IICrazy · Sep 23, 2004

77sleeper said:
they will smoke under certain circumstances and can spill oil at high RPM for sustained periods

jeeze, what a post whore.

Thats how I run mine, it only smokes after i run it for a while.

Breathers and PCV valves

Andy CobraII

New Member

Wart

I'm Mad as HELL and I'M not Gonna Take it ANYMORE!

Blue Thunder

That 70 Car

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zwhitr

77sleeper

GO BUCS!

Wart

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Blue Thunder

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Wart

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Ricky D

TheEvII

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Ricky D

welder4956

77sleeper

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Breathers and PCV valves

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