Inliners International Forums General Discussion Engines need pcv advice

About to order a new aftermarket valve cover, and just looking for the correct way to use a PCV in my 66 292 engine. I have a Clifford intake, no ports drilled in it. I like the look of the side breathers with the 90 degree adapters. Can anyone give me the best way to setup a PCV system on an inline 6 - I've read a few different ideas and just want to order the valve cover with the correct holes cut into it for best performance.

Here's my 1978 setup.



Same manifold port as the vacuum line to the EVAP canister (never could figure out why there are two vacuum valves on it, and one seems to be control by the same temp valve as the EGR). I'm not sure where these manifold vacuum hoses go when you switch over to a Holley 390cfm and either Clifford or Offy intake?

Looking at pictures of the Offy intake online, it looks like there is a port in it to put a fitting in to connect the hose from the PCV to. On the Clifford pics, I can't see where the PCV hose is running to, carb or manifold?

Looking for information on my Evap valve questions I found this article:

http://www.allpar.com/fix/fuel/evaporation-control.html

It sounds like the difference between the two valve Evap canister on the Chevy L6, and the single valve canister on the V8, is that the purge valve is located on the canister in the L6 and part of the carb in the V8. Am I correct here? When one switches from the Monojet to the Holley 390cfm carb, is the purge valve part of the Holley carb? The article recommends replacing the original Evap canister on old cars, as the carbon filter element breaks down and gets sucked into the engine during operation. Or to at least put a fuel filter on the line. So if you swamp a Holley on it, should you just swap out to a new replacement V8 single valve Evap canister and decluter some vacuum lines?

Looking at the routing of the system, it looks like the purge valve and EGR valve are running off ported vacuum on the carb that is controlled by a thermal valve on the water neck. I'm assuming this thermal valve opens when engine coolant is warm and allowing the vacuum to open the EGR valve to let exhaust gas into the manifold as well as draw fuel vapor from the EVAP canister into the same manifold port as PCV. When vacuum is low during idle, both the Evap valve and EGR valve close. And that the other valve on the canister is connected to the line to the fuel bowl in the Monojet, and the vacuum to close it when the engine is on comes from the shared intake manifold port as the PCV and Evap purge valve use. Am I correct in this operation?

BTW, for all those who say just toss the Evap canister, the line to my gas tank was disconnected by the firewall when I got my '78 Camaro. And for months my attached garage smelled of gasoline, with the odor drifting into my basement office when the door was open, until I discovered the disconnected hose. Once I reconnected it, no more gasoline smell. So it's kind of essential for those of us with attached garages.

Obviously with the Clifford and Offy intakes, the EGR valve has to go. And unless you use the stock 292 HD truck manifold with built in valve, the EFE has to go as well. Headers, Langdon manifolds, and the budget 292 tractor replacement 2.5" manifold can't use the EFE, so you just plug the hole for the thermal sensor in the engine block. However I don't see any reason not to keep the thermal sensor and delay valve on the water neck for the HEI vacuum advance.

I had a strange idea of reading the instructions, so I found the Holley model 4106 #0-8007 instructions on Summit Racing. Which had a diagram for the 390cfm carb:



Looks like the carb already includes ports for the PCV and HEI vacuum advance hoses right on the carb. There's another port labeled full manifold vacuum, and recommends it for the Thermac air cleaner, but I'm not sure if it should also be used for the Evap canister? I don't see a line to hook the fuel bowls to the Evap canister tho? Or any indication that the 390cfm carb has the purge valve built in for the Evap system?

Went out into the cold garage and refreshed my memory on the vacuum hose setup:



On my '78 Monojet and integrated head, the HEI vacuum advance hose and THERMAC air cleaner both share a tee off the port on the lower throttle body in the picture. The thicker hose from the float bowl to the EVAP valve is above that. And then the vacuum hose on the upper right goes around to the water neck thermal valve, then goes to a tee where it connects to the EGR and to the purge valve.

That's a little different than the diagram above recommends. From the stock setup, it would seem like the "Full Manifold Vacuum" port should be for the THERMAC and HEI advance, and the labeled "Timed Spark" should feed the Evap canister. And the PCV port would be for the tee for the purge valve and PCV.

But now I see the bowl vents labeled on the Holley diagram. So I guess there is no Evap connection for a Holley, that part of the Evap system can just be deleted. Just the canister and an external purge valve are needed to contain the fuel tank fumes.

@49fastback Well no one has responded about PCV hookup. If you have the Holley 390cfm, looks like you just use the manifold vacuum port at the bottom of the throttle body. You didn't say if you had power brakes too. The Offy has a port for the power brake connection on it, but I don't know if the Clifford does?

Were there any other vacuum accessories you were planning to run on it? HEI advance? EFE flap in the stock manifold? An Evap canister or just a vented gas tank?

49fastback,
I think the answer you are looking for is, use a breather that has a PCV built into it. Push it into the adaptor bolted to the side of VC. Use a regular breather on the other adaptor.

Tom, some of the reading I had done indicated that maybe the PCV needed to be below the level of the breather. So, that's why I was wondering if there is a better or different way of running the PCV. My original thought was to just use two of your adapters and do as you are saying - breather in front and pcv breather in back and plumbed around the back of the valve cover to the intake side. I'll be ordering that valve cover soon!

Hmmmmm.....I never heard anything before or gave the breather to PCV valve placement. On my '78 integrated head, both the PCV valve and the little elbow for the vent are both in the top of the valve cover. The vent elbow attached to a hose to the filter in the air cleaner assembly, and the PCV attached to a hose running down to a port on the manifold that is shared with the Evap hose. The non-integrated valve cover, the breather hose attaches to the side of the cover with the PCV valve in the same spot as mine. So the factory puts the vent at the same level or lower than the PCV valve, although the filter for it is always higher in the air cleaner.

I would have assumed the manifold vacuum would pull air through the crankcase from one to the other no matter what the orientation?