They did not have any core Duramax engines so I sent them mine to rebuild. They did not clean the block, painted over dirt, rust and old sealer. Returned to me with broken studs and bolts in the wrong places. I dealt with the irritation and put the engine together anyways. I put the engine in the truck, got everything hooked up, started the truck, got it up to operating temp. and noticed a pretty bad coolant leak coming from the pass. side of the engine. After two hours of searching with a flashlight and a mirror I found that it was coming from the freeze plug behind the motor mount. If anyone reading this has worked on a duramax then you know the time involved in it. DO NOT make the mistake of calling this company, you will have a better chance of getting a good ham sandwich from them before you get a good engine. After reading this if you are still dense enough to order from them, after T.S.H.T.F dont bother calling their warranty department, they'll never answer or call back.