PCV valve setup

[DANNY8]

I wanna plumb the PCV back into the intake but not 100% sure how to go about it. So far I've set it up so both rocker covers go into one line, which then goes to the catch can, then the catch can is just venting to the atmosphere. Can I just run a line straight from the catch can to the spacer under me carby?

Or do I have to actually use a PCV valve in the line somewhere?

Also, the line from the charcoal canister, does that just get hooked up to a vacuum port on the carby?

 

[VK SL 3800]

What ive heard people do is run the vent to a vacuum port and have a line running from the bottom of the catch can and modify the fuel pump blanking plate to have a return line for any oil to go back to the sump. (unless youve got a mechanical pump).

The charcoal canister line runs to a vacuum port on the carby and is purged under certain conditions. < Straight from my workshop manual
So im guessing its not under vacuum at all times.

 

[Guzzoline addict]

Leave it the way it is or ,Run one line from a rocker cover to the catch can and have the can venting with small filter ,then run a line from a pcv on the opposite rocker cover to manifold vacuum. You can not run both rocker covers inline.

 

[DANNY8]

Here's a pic so ya can see wat I mean with how I have the PCV setup at the moment.

I have both rocker covers going into a t-piece then into the catch can which vents. But I wanna run a hose where the air filter on the can is to the base of the carby to make it legal. I'm not to worried about having a drain back system for the oil just yet, just wanna get the pcv sorted. If I run a hose straight from the can (where the filter is) to the base of the carby, wat will that do to my vacuum as it will be getting the pressure from the crank case, obviously not enuf to make the intake pressurised, but will it work against anything?

 

[ari666]

ok its early, so if this answer is wrong, ima blame coffe-withdrawls:

PCV should be attached onto the large vacuum port on the rear of the base of your holley, and it has full vacuum drawn from the base of the secondarys. you MUST have a PCV (but in your case 2, one in either rocker cover) or you will be losing manifold vacuum by constantly sucking in crank case fumes. now the reason i am not sure the answer is right is cos' for the life of me i cant remember which way the pcv closes... from memory if you suck on the pcv it locks? and if you blow on it its free? or is it the other way round.

cant remember, sorry useless answer.

 

[dirt drifter]

i think the pcv is open under vacuum/light load running then closes up under no vacuum/high load running so that no oil gets mixed with the incoming air/fuel when the motors copping a hiding. oil mist can induce pinging apparently.

danny8, i see no problem with running a decent diameter bit of hose with a pcv valve from your catch can breather to the carby vacuum port

 

[Guzzoline addict]

Just noticed i got i wrong in my first post so ignore that. I think to make it legal ,You run one hose from the pcv valve on a rocker cover to the the catch can then a hose from the catch can to manifold vacuum,then have a hose from the opposite rocker cover to the air fliter(You might get away with just having a fliter on the rocker cover). Just make sure you dont have any vacuum leaks on the catch can.This way air should get draw in one rocker cover and vacuume the crank gasses out the other ,while catching the oil before the vacuum goes into the manifold

 

[DANNY8]

Thx for the replies.

Just noticed i got i wrong in my first post so ignore that. I think to make it legal ,You run one hose from the pcv valve on a rocker cover to the the catch can then a hose from the catch can to manifold vacuum,then have a hose from the opposite rocker cover to the air fliter(You might get away with just having a fliter on the rocker cover). Just make sure you dont have any vacuum leaks on the catch can.This way air should get draw in one rocker cover and vacuume the crank gasses out the other ,while catching the oil before the vacuum goes into the manifold

Just sussed out a vid on youtube which pretty much said everything that u said. It said that the PCV valve must be setup so the vacuum opens it, not the crankcase pressure.

Will I lose power from having it hooked up? As if it's sucking in air, the pressure from the crankcase would normally be getting sucked through the carby?....as in if the PCV is vented how I have it at the moment, there would be more air going through the carby? So having the PCV hooked up properly is pretty much a big vacuum leak hey?

And I'm still not sure about the charcoal canister. I don't understand this 'purge' thing lol. Again it seems like it works as a vacuum leak. As the charcoal canister is hooked up to the fuel tank, so vapours flow through, but then the tank's breather is gonna be sucking in air to compensate.....so yeah, it would be like a vacuum leak??

 

[ari666]

there is meant to be a little metal filter on the front of the quadrajet. it has two lines, one is the fuel in and the other is the carbon-can return. without that filter the carbon-can will be incomplete, so you may struggle with that one.

 

[Guzzoline addict]

Not a 100% sure on how it effects performance,but i think its just a vacuum leak. On standard engine the loss of vacuum doesnt effect it that much .A stardard engine has lots of vacuum at low revs and as long as the vacuum leak effects all cylinders equally( e.g the pcv valve is attached under the carby and not on a intake runner ,so the lean effect can be tune by the carby)it should be allright.However your motor doesnt look stock ,so it might have low vacuum already,making the pcv valve not function properly.