Let's see if this makes sense to anyone here. I have a 1998 Trans am that at 224,000 miles would only use a tad over half a quart of oil every 3,000 miles including leaks. After having a complete rebuild done the engine is now using 1.75 quarts every 3,000. Both the shops that were involved with the rebuild, one did machine work and the other everything else, say that is normal for an ls1. Really? A rebuild causes the loss of an extra 1.25 quarts of oil every 3000? Anyone care to a crack at this one? Any suggestions on what may have caused the extra usage? I'm all ears or should I say eyes.

 

Define complete rebuild please

 

What was done during the rebuild? Was the block honed with torque plates? Did you use the factory rings? New pistons? The word rebuild gets tossed around a lot. A lot goes into a properly rebuilt engine as you are finding out the hard way. I've seen many many engines that ran worse after so called rebuilding. Rebuilding a LS1 that holds up and doesn't use oil is a highly skilled job. The factory built thousands of new engines and had oil usage problems, you can imagine rebuilding same engines that don't use oil a challenge. I hope you find your answer but I seriously doubt it without a complete going over. Could be a simple valve seal issue or piston rings or how it was honed etc. so much needs to be considered. How much leak down do the cylinders have? If you check it do it at TDC and BDC, both matter ALOT. In defense of the machine shop-engine rebuilder these engines are a ball of trouble to start with, anyone that can rebuild one that uses less than 1 qt every 2k is doing good IMO.

I personally use over 2qts every 5k easily in EVERY LS1 car I've owned 5<last one for me> after this one ***** the bed I'm buying a Chrysler product. My Jeep has over 250k and still runs like new. Friend of mine has a Charger that he beats the living **** out of without any of the bs issues GM cars always develop.

Lifter noise-failure Oil-usage Rear failures Next time it rains open the hood and watch the water run all over the engine from the windshield cowling that has about 40 freakin holes in it! I could go on but Christ can't gm build anything that holds up? HELL NO they don't give a rats azz! If they cared about their customers they would have never dropped the fbodies in the 1st place.

My 01 WS6 with 36k easy miles had a bad axle, oil usage problems 1qt every 1-1.5k, bad torsen carrier, broken tilt steering, bad power steering pump, leaking water pump gaskets, bad lifters, broken driver power seat, and now at 88k its using oil like hooker in a hotel room. AND the tilt steering is broken again AND the torsen carrier is one legging again. ****** JUNK!

 

Complete disassembly of block, vatted, bored, honed with torque plates, new pistons, bearings, rings etc. 3 angle valve job new springs, guides and seals. Also upgraded to the ls6 pcv setup.

 

I'm inclined to think it's a problem is with the Rings and/or the hone done on the bores, but it could possibly be a valve seal/s damaged when installed.

How do the spark plugs look, and do they all look the same..?
I'd also check the crank case pressure. There should be some vacuum pull on the palm of your hand when placed/removed from over the oil fill cap hole while the engine is idling. If it positive pressure trying to push you hand away then it's clearly a blow-by problem and I'd do a leak down check on all cylinders to see if you can narrow it down to jus a few cylinders.

 

What new pistons....hypereutectic or forged
are you sure it was bored as the max material removal is only .005" or ten thousandths total bore increase
reason I ask this is that most likely a shop only power honed it out to size If they didn't start with coarse stones, then medium, then fine, with perhaps a final flapper wheel stroke or two, it will have a ring seal issue. either they aren't seating or the moly has been wiped off the primary ring.
Bore finish simply can not be overlooked or shortcut...its WAY more than just getting it to a size hole that the piston fits into.
ANY top notch engine builder will tell you that there can be as much as 20-30 horsepower between a "that'll do" job and "the right way"...not to mention the oil consumption, burning plugs, smoking, high emissions crap.

 

Suggestion - after running it for a bit, like after you get home from work, take the throttle off and see if you can smell a bunch of oil in the intake. Maybe the PCV is defective, and you're oil consumption is through the intake. Easy enough to check, though rather unlikely.

Also, assuming you've already looked for heavy leaks, but it's pretty easy to break a brand new oil pressure unit on the back of the intake during installation. Ask how I know...

 

You had it bored? Why was there a problem with the bores? What pistons and rings were used? Do a leak down and compression test then post up numbers.

 

Is the ring gap correct? What about your clearances? Also do you have any pics of the bore job before it was all put back together? Or any pics of the build that might help one of us to better decide what cpuld possibly be the reason why you're using more oil?

 

Just thought about something...
Which LS6 PCV system do you have ???
The original "old" style IIRC still needs a PCV valve in line in the TB hose
The "new" style uses a fixed orifice (restriction) which is located on the inside of the valley cover.

 

That really bites. Like others have said I am inclined to believe that it is a ring sealing issue.