Guess I'll have to take a look on my LB7 as that probably hasn't ever been touched. I've never dug much into the CCV system on an LB7.
LLY: CCV Scavenging VS Vented to Atmosphere
- Thread starter Bdsankey
- Start date
Guess I'll have to take a look on my LB7 as that probably hasn't ever been touched. I've never dug much into the CCV system on an LB7.
its part of the reason i made modifications to keep the lb7 accesory bracket when i went to an LLY top end. i wanted that factory catch can/vent
Yeah, when I built my motor, I powdercoated everything, and took the factory separator apart to clean after coating. It is really simple. PCV comes in from the left side and hits a single baffle to force the vapor/oil to turn hard downward. The liquid oil (mostly) falls out of suspension and pools at the bottom. The remaining vapor comes back up to the right of the baffle, and out the vent tube that turns back down to the ground. The liquid oil builds up until there is enough weight to open the check ball in the drain valve, and returns to the crankcase.
There is a small (1/4" or less) hole drilled in the back of the catch can portion of the accessory bracket that I believe to be a safety relief in case the outlet tube gets plugged or freezes or whatever. It didn't seem to let any dirt in, probably because it aims at the block and air would have to take a circuitous route to get to/from that hole.
Anyway, at ~300k miles when I pulled mine apart, it was covered in a thin layer of oil residue, and otherwise clean & clear of debris. It had a small amount of liquid oil sitting at the bottom, probably not enough weight to push the check valve open yet.
The only issue I have with the design is the single baffle doesn't do a good job separating oil on a motor with more blowby than stock, as my truck gets some oil out the vent tube that will eventually build up and drip on the driveway. I think routing the vent to the exhaust would solve this, but I don't want to draw a large suction either, as that would probably make the oil separation worse than it is. So maybe I just want a T into the exhaust, not a venturi fitting?
Took my LB7 pvc apart also on the motor build but I plugged the hole in the back drilled/tapped and used a pipe plug if it needed to come out. Mine had oil mist/dirt residue on the motor from the hole in the back before the rebuild. Haven't seen any i'll affects yet, was also thinking it was a afterthought or a just in case hole. I drilled/tapped the fill cap for a transducer to check crankcase pressures under load just haven't got around to setting it up to log yet.
ah interesting!
you know, even with my old block having a hone only and running the 160k miles pistons back in it (loose piston to wall clearance), a broke oil control ring (found one popping a piston out, wasnt from carbon build up at the top either as i clean all that off to see if there is broke rings) and what i consider alot of blow by, i never had any drips. my centerlink, block, trans lines, and frame had a good oil coating build up over 60k miles but that was it.
just t-ing in wont do anything. wont give any suction to the tube and would probably put exhaust into the breather instead. you need the venturi affect to draw a vacuum. i would maybe install a ball valve on the breather instead so you can control how much vac it causes. but honestly, if you put the crank case under vac, you should see less oil coming from that tube than more as windage will be less.
I ran the scavenge setup on the Chevelle. It pulled too much oil out and made a mess in my exhaust. I’ve since switched to a catch can mounted to my radiator support with 2 breathers and baffles in the tank with an oil return line back to the pan. Seems to work much better just need to clean the breathers every so often.
Are you running any kind of check valve? I'm guessing the billet LB7 covers don't have one anymore.
No check valves. Just the sheet metal oil splasher thingy on the rocket shaft assembly. I bent that thing up towards the hole hoping it would help with the oil, but it didn’t. The current catch can works well for my setup.