Oil consumption of more that a quart per 1000 miles or so is (and should be) excessive.
Here is what GM will tell you to do. First, do an oil consumption and dye test (for leaks). The customer will come back with low oil, no leaks and concerned that you are stalling. Then, you will want to fix the lifter guides if they are 'loose', usually new cylinder heads accomplish this but you can get a local machine shop to do the job much cheaper and you may do rings, etc. Once again, the customer will return a little agitated this time. You will now want to replace the engine, and your rep will not, so WATCH OUT. You've already spent a couple thousand buck screwing around and this is the third time back for the same problem.
What should you do? Here's my suggestion. On the first visit, do the dye test and consumption survey and DOCUMENT. Obviously, a 1qt. leak will be obvious (on the driveway) but do the test and consumption survey FIRST. If the problem is real, the second step may be to replace the engine. Why? The cylinders may be out of round, and if they are, there's nothing you can do except a replacement. Pull the heads and have each cylinder measured and DOCUMENT, pictures are a good idea too. There are specific tollerances in the service book (don't know them off hand) and if any cylinder is out of tollerance, the replacement will fix the problem. lIke I said, not every car has the problem as do the new assemblies.
Let me know what you find out.
scott
[This message has been edited by sallen1 (edited 06-16-99).]