I bought a crate motor for my truck in 2004.  I was gone for 18 months over seas and I put 16,000 miles on the motor in the last four years.  My number 6 piston was burning oil like crazy.  I had to put in a new plug every 2 or 3 days.  I took the heads off thinking it was a value.  The heads turned out to be in great working order.  

I pulled the engine and broke it down.  Turned out that the rings were installed wrong.   The pistons looked good and the walls on the block had no ridge.  I bought a set on sealed power rings to install on the pistons.  

But having one huge problem--the Oil rings fit on the pistons but when I try to compress the rings and install them the rings won't go in.  The groves on the pistons where the oil rings go are bigger that the compression ring groves.

I was told that there are two different size oil rings for the aftermarket crate motors.  I never heard of this.  Can any one help with info. or with the right part nubers to buy.   I am getting no help from GM or any GM parts dealers ships in town.  Even the GM dealer where I bought the motor are pushing me aside.  

What engine do you have?  

The engine is a 350.  The motor was made in mexico and Im not getting any help from Watson Chevorlet Dealer in Tucson Az  or getting any help from GM Corp.  I kept getting told that is not there problem and I need to pay a dealer to look at the block and have them fix it.  I'm thinking about buying standard pistons and installing them.   Will there be any size problems?   Any one out there that can help  

Has the block been bored out? Are they GM pistons? The only difference in oil rings that I know of is , standard and low tension. Low tension are the same rings but the spacer is smaller in diameter, for less radial tension. Are you shure your not working with a .030 ring in a standard bore, or a .030 in a .060 bore and so on.  Standard   350 pistons measure, 4.00 in. , so measure your pistons, do the math, and find out if you have the correct rings. Is this a GM reman. or a cheapie from Auto-Zone? I have seen some shady work even in the GM remans. Post your findings, curious to hear your results. Good Luck.  

If I get this right the oil ring grooves in the piston are not deep enough for the rings to go in deep enough to be flush with the piston.If thats your problem look for a replacement ring set for shallow oil ring groove. I ran into that when reringing my 88 blazer.There were standard and a shallow oil ring set listed.Hope this helps .
Jon