Hey guys, I've done some searching around to get an idea on what im getting into and what my possible best solution is.
Brief Info: I have a 2001 Z28 M6 with 110K miles. TSP torquer v2 cam, long tubes, ls6 intake, I was told "ls7 valve train" (I think he maybe ment just ls7 valve springs), ported/polished stock ls1 heads. Stock bottom end. I think thats the main stuff for the engine.
The problem/situation: I've had a a bad oil consumption issue as well as a rich smell from the car ever since I got it. I was told from the previous owner that the issue was from him changing to 60# injectors as well as having the heads ported and polished without having the engine retuned. I got the engine retuned and made some improvements. This is where we noticed the problem. After making a pull on the dyno, as the engine was slowing down there was a LOT of smoke coming from the exhaust. We pretty much ruled it down to valve stem seals or piston rings. I figured it was piston rings since it wasn't smoking under acceleration. Over time came to realize that after around 1500 miles or so it needs about a quart of oil. After a little over 3000 miles and this last time I went to add oil I saw that the oil was PRETTY dark so I'm thinking its piston rings.
Possible Solutions: From what I've read about reringing and honing and bla bla bla, it looks like I should rering it and atleast deglaze the cylinders. Ive heard that if I hone the cylinders there is a chance that I will have to do larger pistons. My goal is to make a little bit more power than I am now (402rwhp/389rwtq). I was thinking I might do high compression pistons but Im not sure what to look at. I know wiesco has some +12cc dome pistons as well as diamond racing has a set of high compression pistons (I believe they are +10cc).
I am not sure what my best route is. I dont want to spend the money on doing a stroker kit. I was only looking at spending the money on new pistons and possibly rods... I dont really want to do boost later on and not worried about spraying. Long run goal is to have a bitchin hot rod that I will daily drive. Im not worried about it having SUPER streetable characteristics... its a hot rod for damn sakes...

 

If you are looking for more compression its much cheaper to get smaller cc chamber heads, rather than getting new pistons which will have to rebalanced with the rotating assembly...also dome pistons might limit the cam you can run..

 

Might not be piston rings as much piston clearance, Might want to check it carefully because I know lots of GM shops replaced piston rings in LS engines without solving oil usage problems. Get one loose piston or a worn piston like number 7 and there goes the oil out the tailpipe.

Also a loose-worn piston will allow lots of combustion crap to contaminate the engine oil. One of mine had a loose no 7 piston and I had high oil consuption and black as coal oil all the time. I managed to get almost 100k out of it before the piston broke, but it used alot of oil.

 

any certain way to diagnose a worn/loose piston or piston ring issue without digging in the engine?

 

If you are going in to rering anyway its not much to measure the bores and pistons. If there are any worn or loose you will see the wear on the piston and cylinder walls. You could use a bore camera and take a look in each cylinder to see if there is excessive wear in any bores. Sometimes a leak down test can give a general idea but is nothing like pulling the heads off and checking things. The spark plug in worn cylinders will look oily, might want to pull them all and see how they compare to each other. Will give some idea which cylinders are using oil. Classic LS1 worn cylinders are number 7, 5 and 8.

 

Try the rocker arm bolts.

Usually the first thing everyone does when they port these heads is to remove the bump inside the port underneath the rocker. When you do that, the bolt protrudes into the port, and if thread sealer is not used, the vacuum will pull oil into the engine. If the seller told you it had an LS7 anything in the valvetrain, chances are no one put thread sealer on those threads.