H/C/I/E C6 Z06 smoking under WOT
 

Hey all, im having some trouble narrowing down whats causing my Z to billow out some smoke under WOT pulls. Im also getting some very LIGHT smoke at idle (as in the sunlight has to be in the right spot for me to see it). The car consumes about a quart to a quart and a half of oil between oil changes. Im running mobil 1 5w 20 currently but i have ran the VR racing 20w 50 before and still had the same issue, also currently have a catch can on the car. Ive replaced the valve guide seals and performed a leak down test which came back good yet the problem still persist. The car runs great power wise, traps 10.45 at 133/135 range which seems to be on par with car z06s with similar mods, i just want the car to stop looking like the union pacific going down the track. Heres a list of mods if it helps anyone point me in the right direction.....thanks to anyone that can help

AHP heads milled .040
MSD intake
LS7R cam
TSP longtubes and catless mid
Flex fuel sensor (e85 and 93 mix)
Catch can (dont know the brand)
NW102 TB

Dont want to go sideways on your thread but...wtf are you running 5w20 for?!

Not all brand catch cans work the same on our (dry sump) cars. Have you pulled the TB and looked inside your intake manifold to see if you have oil in there?

yea I've had the manifold apart recently and didn't see any excessive oil in it...maybe a light film but not small puddling or anything of that nature. Back of the throttle body didn't really have any oil on it either

well I believe the cap says 5w30...and at the time when I went to the parts store they only had 5w20 Mobil 1, I personally dont think it makes a big difference with the amount I drive it.

Smoke under power is almost always ring seal

that's what I've been told. But the leak down test came back good and the car has 55k on the clock. Could it still be a ring problem that a leak down wouldn't catch?

thats fairly low miles as well. have you done a leak down on yours yet?

What was the actual leak down rate? Probably rings or valves unless your somehow pumping oil into the intake.

Really? Who said that 5W20 was good for an LS7? First thing I would do is install the correct oil.

A difference of "10" in the upper temp weight range is fairly significant. And the "amount you drive it" has nothing to do with the type of oil you should use. Ugh.

This is what blows my mind. GM says 5w-30 for the Gen V LT1 but 0w-20 for the same motor in the truck, (L86.) Now, GM is telling you not to put 5w30 in the LT1 but instead their new lower SAPS 0w-40 ESP, but the 0w20 is still good for the same motor in the trucks. They're sounding like the Broward County Board of Elections here, I just don't think I trust them. Emissions will always be secondary to the longevity of my motor when it comes to motor oil.

Interesting viscosity levels between 0w40 and 5w30, not a huge difference. But look at the 0w20, that's a huge difference compared to 5w30. Sure, the L86 is tuned for a truck, has a slightly different intake and exhaust manifold, but its otherwise an identical long block with the same internal tolerances.

https://cimg6.ibsrv.net/gimg/www.cor...f54b683ffb.jpg
https://cimg0.ibsrv.net/gimg/www.cor...9218ccfe58.jpg

That is the irony of it all - they are the exact same motor otherwise; exact same long and short block. Sure, there is more cooling in the trucks and they are tuned differently, but they are otherwise the exact same camshaft, cylinder heads, 11.5:1 compression ratio, main bearings, VVT, AFM, etc. The intake manifold is different (taller for more low-end power) because there is more room in the trucks under the hood, and the exhaust manifolds optimized for use in the trucks.

Lower weight oil = emissions regulations to reduce MPG.

to each their own I guess. I know the owners manual specifically says not to run a 20w oil but I have personally seen people run and praise the VR racing oil on their ls7. So take your "ugh" and move along