Hey guys, I've put a LY6 into my Chevelle. Can someone tell me if the way I have the motor vented is good enough? I'm thinking it is not as the front of the valley cover has started pushing oil out and I'm getting oil seeping out around the oil pan bolts (not the gasket) after only 700 miles. The engine hasn't used any oil and doesn't smoke and all the data looks great. I've got lines plumbed together out of both valve cover nipples and into the catch can then out of the catch can and into the throttle body. The line on the throttle body doesn't feel like it pulls much vacuum though. Any advice is welcomed. Picture of the engine below.

 

Is the line to the throttle body hooked up to manifold vacuum, or is it before the throttle blade? It needs full manifold vacuum to draw effectively. And it should be pulling filtered, measured (by MAF) air into one valve cover, thru the engine, and out the metered hole in the other valve cover, to the catch can, then into the manifold vacuum port.

 

My drawing sucks but below is how I currently have it plumbed with the Mike Norris catch can and per Holley this is a PCV passage on their Holley EFI Throttle body. The 2 black lines represent the stock valve covers, the blue lines represent the hose into the catch can and the red line is the hose out of the catch can into the throttle body. In the beginning I had a breather on the passenger side valve cover. Also the engine is speed density not MAF.

 

Where's your fresh air inlet? Need to develop an air flow pattern that sweeps the crankcase. Seems like what you done is just let the engine build crankcase pressure and spill out the top.

 

I'm open to any advise y'all got. I thought having the breather on the other valve cover would do that.

 

Cruise conditions are different than full throttle. Cruise has vacuum, full throttle doesn't.

Cruise: You want to set up an air flow path that sweeps the crankcase. Vacuum is your friend in this situation. Air moves from High pressure to Low pressure. The High pressure zone is the outside atmosphere. And the Low pressure zone is the engine intake manifold (that's in vacuum during cruise).

1. Let fresh air come into the valve cover. Either take the air from the engine air filter box, or mount a filter to the valve cover. Both are sources at atmospheric pressure. It's more environmentally friendly to use the air filter box so that the engine burns any gases that vent out the valve cover.

2. Connect the valley PCV hose to intake manifold. This is the low pressure side that completes the air flow path. Air comes in the valve cover --> sweeps the crankcase --> travels up to the center valley and into the intake manifold. A catch can is used to intercept and collect oil that might come out the valley cover.

Full Throttle: There's no more manifold vacuum and the manifold is at the same pressure as the valve covers (atmospheric). The crankcase pressure goes even higher (more blow-by past pistons) and the crankcase gases & oil droplets spew out every orifice of the engine.... Valve covers, valley PCV hose, weak seals.... whatever and wherever it can escape. This is when venting the valve covers saves the day.

1. Racers will reconfigure the PCV. They unplug hoses from the manifold and add vents to both valve covers. The catch can is used to intercept and collect oil from the valve covers. Racers might also add a vacuum pump on the valve cover in order to evacuate the crankcase.

2. Street car will still have the PCV system meant for cruising. Crankcase pressure & oil droplets will vent out PCV valve, valve cover, wherever it can. This is when things get oily messy for some people. Most the oil will come through the PCV valve in the valley cover, so people tend to favor putting the catch can on that circuit. Valve covers have pretty decent oil baffling and very little oil is lost that way. More venting of the valve covers helps with the oil loss situation through PCV hose (uncorks the engine so crankcase gasses can escape through valve covers). The way the factory does it is the 1LE cars have a big vent that screws down in place of the oil fill cap. The vent has an oil separator and ties into the fresh air intake (air filter box). If the oil separator isn't enough and oil puddles out of the vent, then that's the time to consider a catch can on that circuit too.

 

It looks to me like the port on the throttle body is meant to be a supply air for the pcv system. That line should go to the passenger side vc. There should be a line from the driver side vc to the catch can and a line from the catch can through a valve/orifice to manifold vacuum.

 

The line on the throttle pulls some vacuum, I have verified that by putting a hose on it and running the engine.

 

This weekend I put a small K&N filter on the drivers side valve cover then just hooked the catch can only to the drivers side valve cover then to the throttle body.

 

Question: Do you want to utilize the intake manifold to pull air through the crankcase "PCV" or would you rather not have all the blow by and moisture going back into the intake manifold to decrease your octane and gum up your engine?

If your answer is yes then run a sealed catch can off of one of the valve covers, "Usually the driver side as the newer LS valve covers had an orifice built into it" and then to the intake manifold or if you have a valley cover with built in PCV then run the sealed can between it and the intake manifold. If your running valve covers that just has a 3/8" line connect with no orifice then you may need to run an inline PCV valve and as for the other valve cover just run a 3/8 line from it to the throttle body or the air duct before the throttle body.

If your answer no then I'd suggest investing into one or two breather cans and running each valve cover to a breather can. I'm utilizing one breather can with 10AN lines of each valve cover on the 427 and other than having to drain water out of the can during the cold months all has been good.

 

I have used the Norris can and the line from the driver valve cover should run to the top of the can and the bottom outlet of the can should go to the intake manifold. The passenger valve cover should run to the throttle body or the air duct before the throttle body. Another trick is to use RTV sealant to make a cone up on the threads at the head of the bolt and then run them down on the pan and the other covers.

 

That's just setting up a miniature air loop where fresh air comes in the filter and goes right back out a few inches away. It's not sweeping the crankcase. Also might act like a vacuum leak as far as the engine is concerned.