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I saw the exact same thing.
I took the catch can off my car and my oil psi shot up 4lbs.
John,what causes too much vacum in the crankcase?
How can u eliminate it,breathers?
Ideally you want a little vacuum in there. The pcv normally does this. If you remove the pcv, and use a breather, then any pressure that builds up just goes out through the breather. You never see any vacuum then, if the pcv is removed. But you may get some blowby and oil coming out of the breather and getting on the engine or firewall.
The reason it affects the oil pressure, is because the oil is constantly escaping out of the bearings. If you had 40psi of oil pressure at regular atmospheric pressure inside the engine, for example, and then somehow you could pressurize the inside of the engine to 40psi, theoretically the oil couldn't get out because the pressures would be equal, with the air pressure trying to hold the oil back. But the oil pump would still be pumping, so the oil pressure would continue to build up until the oil started getting out again. And if you have a vacuum in the engine, it is trying to suck the oil right out of the bearings, so the oil pressure is less in that case.
The old rule of thumb for oil pressure was 10psi per 1000 rpms, to protect the bearings. I don't know if that rule bends a little for the LS1 engine or not... As long as your oil pressure is within factory specs, I'd say don't worry about it varying with or without the pcv connected.
(a plus of having a little vacuum in the crankcase, is less resistance seen by the backside of the pistons, and a little less air friction seen by the crank) At 4" away from crank centerline, when turning 6000 rpms, things are moving at over 209 feet per second, or 143 mph....
John,I have my valve covers tee'd and one pcv valve in the stock location working for both valve covers.Do u think it would benefit me to elimenate one side of my pcv and adding a breather to that cover?
Some people dont like running a breather and a pcv together.
Whats your take?
__________________ JS 2010 Toyota Corolla S Bone Stock
if you go with a breather you need to remove the entire PCV otherwise you will get unmetered air (air that didn't go through the MAF) into the intake manifold and this will cause issues with your tune.
I would rather have a breather and no PCV as it prevents any oil from getting into the intake system. I had to run a PCV on my old engine because it had some cracked pistons (had to keep it driving till summer/class was out) but I will run a breather on my 388 for the above reason.
The only time the breather sucks is if you have lots of blowby because the oil will smoke and come out the breather and billow out under the hood (ask me how I know this... ).