Volume III, Issue 5, Page 22

Oil Control

It’s better in the crankcase than in the atmosphere.

The slow transition of my car from a near-race car to street car continues. My latest escapade is that I discovered my car had a real thirst for oil through the positive crankcase ventilation (PCV) valve.  During a routine oil check, I discovered the engine was a couple quarts down. Since I had just changed it about 500 miles ago, I was immediately concerned. Reports of a puff of smoke during deceleration at the track started to make sense now. 

I pulled the throttle body off the intake manifold to find just what I feared…and hoped for. I was hoping to find oil in the intake manifold because the alternative was much worse. I really didn’t want to go chasing valve guide or piston ring problems. But I didn’t have to: I could practically see my reflection in the shiny oil inside the manifold plenum. 

I was using a set of cool billet aluminum valve covers, along with a racy looking PCV valve on the driver’s side cover. I had plumbed that to a vacuum port in the intake manifold. And man, did it flow a lot of oil!  The reason is that the PCV valve wasn’t baffled and that it actually sits right over top of the #7 exhaust valve pushrod. Without any baffling, and with good vacuum (the Lunati Voodoo cam really keeps engine vacuum up), it was pushing oil to the tune of a quart every 200 miles or so. I had two problems to solve: a lowered oil level that could lead to engine failure and burning oil at the expense of horsepower. 

The fix was pretty obvious: time to ditch the billet valve covers and use factory parts. I snagged a pair of GM’s original covers from a fellow at LS1Tech.com, a new PCV valve from the Chevy dealer, and I set to work. There have been reports of excessive oil consumption via the PCV on the LS1 from the day it debuted in the 1997 Corvette, so I asked my friend Mike Norris for some advice on how to proceed. I don’t have a factory throttle body, so it wasn’t obvious to me how to go about it.  I didn’t want to just connect the PCV back to the same port in the intake manifold with a properly baffled valve cover if I would have the same problems early LS1 engines had. Mike told me that lots of people use a catch can between the PCV and the intake manifold to collect the oil rather than burn it.  

The idea is that the baffling will greatly reduce the amount of oil being sucked out of the engine, and that the catch can will collect the small mount that does.  And the two together will keep the intake manifold flowing gas and air, not oil.  

There’s more to this story: since air is being sucked out of the engine, air needs to be allowed to flow in as well.  Factory cars use filtered air from behind the intake air filter, but that can also provide a non-baffled path for oil to flow from the crankcase to the intake.  Instead, I’m using a small dedicated filter connected to the air inlet nipple on the passenger car valve cover. 

The challenge is to take this new plumbing and make it attractive.  I’m still working on that, either by hiding it under the air filter or by running under the fuel rail. 

I am really looking forward to driving the car without having to check the oil level every time I take it out for a spin. That’s OK for race day on a race car.  It’s a real hassle on a street car. 

 

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