Joshboody

I posted in Tech section for feedback and wondering if anyone here sees a bunch of oil usage?
https://www.corvetteforum.com/forums...on-advise.html

I'm consuming about 5qt during a track day... 4 sessions at 20min. Car runs great.
- smoking mainly on throttle, but more initial puff during corner exit or rev match gear change.
- 2 catch cans maybe catching 1/5 the total usage
- changed valve seals to 1pc with mild cam... but don't remember if usage increased after.

Always just assumed oil was blowing past clean side at WOT, but with 2nd CC added recently this is not the case. So I'm guessing the rings and will just run it til it breaks.
- compression test, 1 cyl about 10% down.
- Cold leak down 6 - 9%
- spark plugs look good... no oil fouling

2001 C5 LS1 (10/2000), 110K miles, >50 track days

Thanks for any advise!

davidfarmer

I can't think of anything good that would be causing this. You have a healthy block (for now), I'd probably consider refreshing it while you still have a good core. Engines aren't as easy to find as they used to be.

truth.b

I agree with David. My drysump LS3 had 126K and let go recently. Up until it died I saw little to now oil consumption at the track or on the street. Currently in the rebuild process and long story short it was much easier/cheaper to rebuild it than to get a new motor. In the end, I'll have a stronger motor with a healthy block and a known history.

fatbillybob

I have many thoughts. 1st please post pic of your catch can hoses set up.

TrackAire

Wow, that's a lot of oil. I would highly recommend looking at how the catch can set up is routed. If incorrect, it will drink oil like crazy....I've seen people lose engines due to a "tuner" installing the catch can incorrectly.

Let's hope it is something as easy as this. Post pictures of how the hoses are routed into and out of the motor/catch can so others can take a look.

Good luck on finding the solution!!

Joshboody

Thanks for the feedback. I hear ya on rebuilding... rebuild or part out and buy racecar... decisions.

I'll take pic of the CC setup when I get home.
- 2004 LS6 pcv conversion routed to CC.
- Added 2nd CC recently, expecting a bunch of oil but just some.
- manifold looks pretty clean with flashlight
- vacuum at dipstick with clean side plugged, 10" hg and climbing / 0" with clean side open... so seems working correctly, during idle at least.

I use this style but ebay sourced... little diff oil media I think.
http://www.mikenorrismotorsports.com...atch-cans.html

sccaGT1racer

From what I seen on the ls1. Its probably got a broken piston. They like to break the ring land between the top and second ring. If you catch it soon enough it will clean up with a .005 overbore. Summit has some nice pistons now for the application.

froggy47

You think it'll still run hard for those minutes with a bad land? That's actually a tuff little engine if so.



I'd have thought it would grenade.

Joshboody

There's no obvious signs of 1 cyl worse off. Leak down and spark plugs are consistent.

Joshboody

Pic of my CC setup
- Left side CC, upper hose routed to VC... can’t see in pic
- capped both side rear VC nipples like LS6
- right side CC routed between LS6 valley cover and manifold vacuum.


This is how LS6 is plumbed, just with CCs inbetween.

fatbillybob

What I have learned about the LS pcv is no one really understands the whys. Many think they do. That's why catchcans keep coming up every few months when a new person start tracking or gets a new motor. All I can say is baring a real engine defect there are motors that make the right HP and torque and blow lots of oil and some that blow no oil and some that blow some oil. The LS motor is the box of chocolates you never know what you are going to get after the rebuild. No one really understands why because if they did we could build perfect HP/torque producers that blow no oil and these threads would not exist.

That said what I would do is go on the dyno and see if you are making the right HP and torque. If you are then the motor is fine. You can refresh but where do you draw the line? I personally draw the line at rebuild or just run it until it needs a rebuild and that means I'm no longer making the right HP/torque.

So assuming your numbers are good when a motor blows no oil you can race without catchcans. That is how my original '04 LS6 motor was. It used no oil! Then there are motors that blow a little and the typical catch cans you see like you you set up or various mighty mouse setup work. Then you get the real oil burners. I have had the real oil burners and learned what to do from other crew chiefs with oil burners and here is what you do. If you got a real oil burner switch your catch can PCV system from Positive crankcase ventilation to passive crankcase ventilation. I wrote a thread while exploring this called ultimate catchcan on this board. It was an infantile thread but had nice pictures. It tells you how I made a passive crankcase ventilation system. Basically the goal is not to plumb into the suction side of the intake. I use zero oil by the way and really do not need the drainback into the dipstick tube since I use no oil. If I plumb the typical catch can way like you have in your picture I will suck oil just like you bigtime.

A second way to control the oil is to combine the typical catchcan setup ala mighty mouse with a home made oil baffle pan placed into the valley. This makes the oil vapor condense and drop back into the valley before it gets sucked out the 0.040" orifice PCV venturi at the valley cover. This home made baffle is like the baffle in the oil pan or in the passenger valve cover. It basically acts like an oil separator to slow down the amount of oil that can leave the motor.

If I am rebuilding a motor or just got one rebuilt I would add the valley oil baffle because the engine would already be out and easy to access. If the motor was already in the car I would just make a passive crankcase ventilation system.

Anyway, I hope that gives you some ideas. That's all I got.

sccaGT1racer

Here is what a crankcase vent system that works. Ive been using this system on wet sump road race cars for 20 years.

sccaGT1racer

Ive had 3 ls 1/6 engines with broken pistsons and rings lands in my shop over the last year. They were all autocross/hpde cars that see rpm's and hard use. They all still ran but had various signs of failures.

Joshboody

I don't think this is CC ventilation related... I'm only catching 1/5 of the usage in my CCs... unless oil is blowing past the CCs. Really seems to be rings, but its uniform between all cyl based on leak down and spark plugs.
I could see issue with CCs creating higher pressure and "pushing" oil past the rings. But compared to others with breathers, I should be flowing more vapor.

FatBilly, I like your idea of a dyno to assess the engine.

wtb-z

What were the other signs of failures that brought those motors in?

sccaGT1racer

Intermittent check engine light with a misfire code stored , smoking under accel and decel, random slight knocking noise, using excessive oil.

maj75

I had this exact issue with a new motor in my ‘99. I was using almost a quart every session. Catch can would almost be full. Took it back to the shop and they changed the LS6 valley cover. IIRC, they said a baffle in the valley pan fails and allows full vacuum to the PVC system which pulls too much oil out of the crank case and into the intake tract.

After the valley pan was replaced my oil consumption is back to normal. Maybe a tablespoon in my catch can after each session. Nothing discernible on the dipstick.

fatbillybob

Something in the valley cover is an interesting possibility which also explains why the homemade extra valley baffle seems to cure blowing too much oil.

Joshboody

Update, discovered my eBay clean side CC may not be working properly so I’m pulling it. Potentially higher volume oil is going through clean side at WOT than determined initially. Still a bunch going thru motor though. Eliminating the 2nd CC for now.

My thinking for next routing:
- currently 1 clean side hose from intake to single VC port, like LS6
- I’m thinking to tee 2 (or all 3) VC ports and rout to intake... this way 1 VC baffle isn’t handling all the flow.
- DR side VC doesn’t have baffle though... maybe check valve or separator could work only at that 1 port.

Joshboody

Update 2
- catch can prob fine, but took the filter media out
- looks like front seal is leaking... thought was catch can at first.

Testing today
- added second clean side vent from both rear VCs tapping the air bridge (pic below)
- this seemed to work well in minimal or no front seal leak
- ran 15psi gauge to dipstick... seemed less pressure with 2nd vent but hard to tell at WOT looking at gauge. Maybe 0.5psi vs 0.2 between 1 and 2 clean side vents.
- blocked intake and just passively vented... this puked crap ton oil from front seal... nixed this idea.

Smoking
Only time I can see smoke is after WOT to upper rpms and let off, then give “slight” gas... this produces a CLOUD. Happens with blocked intake so definitely rings or seals from the high vacuum.
Rings or seals?? I can see reasons for either with vacuum pulling oil.

I’d love to try a finer pressure gauge, like inches of water, but they spensive! One concerning part with gauge is the fluttering needle when letting off at high rpm... of course closer to 0 you are the better.

Anyway, next action I’m not sure yet. Prob drive for a bit with the 3 vents to the intake watching the front seal.