I yanked my intake manifold off since I needed to relocate my oil sending unit to behind the intake and I was rather shocked at what I saw when the manifold came off

Mind you I have a catch can on my motor (that I put on even before I fired it up) so I thought that I would be safe from oil injestion but that just doesn't seem to be the case. Here's a quick pic looking at #6 intake runner. I wiped the top half of it so that you could see how much oil is really there......how disappointing

And in case you're wondering, this motor only has about 2000 miles on it and it is not driven hard at all...it's my daily driver. Doesn't appear to use oil or smoke.

 

Your thread title says, "sucking oil"

The last sentence in your post says, "Doesn't appear to use oil or smoke".

Whats the deal?

Anyways, I think catch cans are bullshit, they do nothing. Catching a few drops means "nothing."

You need new valve seals by the looks of that runner.

.

 

yes, catch cans do work otherwise theyd never be used.. also its very possible to eat oil so it doesnt smoke but is a noticeable loss

 

Agreed.. our ls7 has the same issue unfortunately

 

John B, do you have a picture of how you ran your catch can? I need to add one to my ls7 Headed 427 also. When I was on the road course last time I was having alot of problems with sucking in oil from the valve cover. When you are in a hard right turn to much oil stays up in the valve cover and then get sucked into the motor.

 

How much oil are you collecting in your catch can? Maybe your PCV valve is bad? I'm collecting about a teaspoon every 300 miles on a stock internal motor.

 

Why are you even running a PCV setup on the motor?

 

I think I have tried everything, diff valve cover PCV setups, catch cans, LS1, LS6, LS2 valley cover and all anyone could dream up but believe oil in the intake is a fact of life.

 

It isn't "oil" persay passing through... it is the vapors making their way through and collecting up, which unfortunately is going to be there no matter what.

I put a breather on my 408, the vapors are still there, just being released to the atmosphere instead of back into the combustion chamber.

 

Are you wicking oil down the threads from the rocker arm bolts? These bolts fully enter the intake runners on C5 heads, I'm not sure about the LS7, but I wouldn't be the least bit surprised if they do. At high vacuum such as idle or normal cruise, you can pull a fair amount of oil past these threads. Use ARP thread sealant and see if this helps.

Chuck

 

not second guessin you but I am about to start a LS7 project and found that if teh lines are crossed on the dry sump, it will suck a lot of oil. I plan on using a filter style catch can, to catch the oil vapor trapped in the air, if that dont work, I plan on using an electric air pump and seal the intake off from PCV system.

 

I mounted it on a bracket off of my custom A/C bracket (pic enclosed).
There isn't one with the catch can.
I haven't looked yet....I'll have to open the can and take a peek.
Shouldn't be. I haven't looked but I don't believe the intake bolts pass through the intake runners on these heads.
The lines aren't crossed

 

This could be part of the problem. All the catch can does is pull the oil from the air, if you don't run a PCV valve then the intake will be pulling air from your crankcase all the time. It should only pull air when the crankcase is trying to push air out with positive pressure (Positive Crankcase Ventilation). Does the LS7 have a valve hidden somewhere else maybe?

All I do is open the petcock on the bottom of the can and let it drain into some paper towels. I do this fairly often. It helps if the engine is warm because that stuff tends to get fairly thick. Of course, if you have never checked it and with no PCV valve the can could have filled up. If that's the case then your intake would be sucking liquid oil strait into your intake. That wouldn't be good.

 

The OEM set-up has one I believe. Good point, I may just add one and see what happens...can't hurt!
Just checked it and it has about 2 ounces of oil in it.

 

I also need to investigate the PVC set up so I would be interested in what you discover. The catch can needs to be "uphill" from the tank. The vapors and goo that condense in the line can then run back into the tank when the car sits and cools. Probably not going to effect oil in the intake too much unless you do put a PVC from the overflow to the intake. Then you could get puddling in the line from tank to catch can and it could get drawn into the intake.