Rebuilt LT1 that burns oil?

[94_Formula]

I have a 1994 Lt1 it currrently has 4,500 on a rebuilt engine. At 128,000 a head gasket wen't so I pulled the motor and sent it to a machine shop which I've done prior business with before. Now at 4,500 it burns oil actually it burns 48 ounces in 1000 miles. If anyone knows why this is happening please post what they think.



Thanks,
Joe

[fastTa]

Did they re-hone the cylinder walls? Did they replace the rings? Did they replace the valve seals?

Sounds like to me if you are using that much oil that the piston to cylinder wall clearance tolerances were not matched properly or at worst case scenario they did not even touch the cylinder walls leaving them slightly out of round. The "outside" (side opposite of camshaft) of the cylnder wall is called the thrust side. This is the side of the cylinder wall that takes the most wear from the way the piston is naturally thrust against this side of the cylinder wall. The higher the mileage and the harder the motor was used the more this will eventually create the cylinder wall to lose it's perfect cylindrical shape. This doesn't allow the oil ring pack and even the other rings to make proper contact with the entire cylinder wall and thus allowin oil to "blowby".

Usually a rebuild consists of at least a light bore that needs to be done with at least a torque plate, and a fininsh hone. Normally most machine shops will bore .030" over making the overall cylinder bore 4.030". They then should use a piston designed for a 4.030" bore. Ask your machine shop to give you their finish tolerances on the cylinder bores. Each cylinder should not mic out to more than .0002" tolerances in any instance.

Also have you checked for any external oil leaks? Just make sure gaskets such as the oil pan, timing cover, rear main seal, and intake manifold are externally oil free.

Didn't know you were getting a book did you!