rolley89

Ok, here is what I have going on.

I swapped an LQ9, ls1 intake, cold air kit, long tube headers (all the rest is stock) into a 67 Chevelle.

I had a DTC code come on (lean bank 1 and 2) Looked at my Short term and long term fuel graphing and it was off the charts. After looking everywhere for intake leaks, I finally pulled the tubes off the intake that lead to the right and left valve cover, capped the holes on the intake, and left to tubes open to atmosphere.

The lean conditions went away and the DTC cleared, YES!!! went for a cruise, got on it a few times, got home and oil was puking from under the car..... Blown rear main seal....

My oil pressure reads 60 psi, connection is at the Holley pan for my VHX gauges (not sure how accurate that reading is)

My question: By pulling off the valve cover tubes from the intake, would that cause a main seal to blow?

How should the valve covers be vented? under vacuum or can they be fitted with a breather?

I have no PCV system, working from scratch here, thought the tubes to intake was all that was needed..

Any help is greatly appreciated. Pictures of the valve cover venting would help too.

Thanks guys!

S10xGN

iTrader: (11)

Mine puked too, I realized after I replaced it that my aftermarket covers were not vented. After adding a breather to each cover, the new seal has never leaked a drop. I might have been able to get by just by adding the breathers, maybe you will too. They were just some "top-fuel" 60's looking finned breathers...

rolley89

I will probably have to go the route. I just want to make sure, cause the work to replace a rear seal, on a garage floor and Jackstands...is not fun...

S10xGN

iTrader: (11)

Just pull the valve cover filler plug and drive it, should be enough of a vent to tell if the seal needs replacing...

ckpitt55

iTrader: (4)

The PCV system works by drawing out crankcase gases using manifold vacuum, but you also need a clean air supply from the throttle body to backfill what you're pulling out of the crankcase.

Since you've disconnected everything that would stimulate flow, maybe the gases are stagnant in there and just built up to the point that they blew out your seal. How many miles are on the LQ9? Leakdown numbers?

As for what was causing the lean condition...apparently you had a leak somewhere in the line connecting to the intake since it went away when you capped it, preventing unmetered air to enter. Did you find any cracks / tears in the lines you disconnected?

bczee

iTrader: (12)

If you removed the PCV System / Tubes and plugged the ports. There would be no way for any internal back pressure to escape. The results of a closed system is usually blown main (and/or other) seals.

Using breather would have prevented it.. but having a PCV system not only helps the emissions but also to create a vacuum inside the crank case, if enough vacuum is there, it also helps to seal the piston rings... If your worried about oil being sucked into the intake... use a catch can inline with the PCV Before it gets back to the intake.

If you left the fresh air tube on and plugged the PCV ports. It is possible the oil and vapors were being sucked into the intake via the fresh air tube. If using breathers, the fresh air tube should also be removed and plugged.

Good luck on the seal replacement now. Let us know how things work out.

BC

rolley89

There is 100k on the motor, leak down numbers? I have no idea. All tubing was new, with the only possible leak being the filler cap directly on the cover (not using the plastic elbow)

rolley89

Motor had no PCV components, I plugged the egr hole on the intake and ran a tube from each valve cover into the intake, after the MAF. Is that the normal way to go?

truckdoug

iTrader: (25)

nah that just draws from metered atmospheric pressure air

you gotta draw vacuum on one side of the system. it's typical to use manifold vacuum, ie on the engine side of the throttle body.

i ended up with catch can in my system. these motors can move some oil around!

pdsq98gt

You need to hook the nipple on the right valve cover to the port on the throttle body. Then the port on the rear of the left valve cover hooks to the port on the right of the intake just behind the throttle body. You can run a hose around the back of the intake to it. This is assuming you have stock lq9 valve covers.
Here's s pic of mine. You can see the hoses on the throttle body. The one that disappears goes around the back of the intake to the left valve cover.

rolley89

Thanks guys for the input. I have a DBW throttle body, so it doesn't have a port. So I ran both hoses to the throttle body. And came up lean. If the hoses were in front of the MAF I bet the codes go away, but I have never seen them run in that fashion.