I paid a Turbo Buick specialist a lot of money back in the 90's to build a engine and install it for me. With the transmission rebuilt, fuel pumps, cooling system, exhaust, turbo, injectors, aluminum heads, roller rockers, cam, JE Pistons, BMS rods, down pipe and several other things I don't remember I had spent $15 k . I told the shop owner I wanted to keep my stock engine since there was nothing wrong with it and was charged for a "core" for the block but when I went to pick my car up they had disassembled the engine and I was told he had sent my old block to the machine shop and it had already been bored for another customers build. Instead they had cut a couple of my rods and they were in a box with the pistons. This had me pissed to begin with but the damage was done. I was told to take it easy on it for the first thousand miles to let everything break in. Within 300 miles driving Ms Daisy style the transmission stator broke leaving me on the side of the road. That was replaced for free but I was accused of not breaking it in properly. By 1k miles I had taken it back to the shop that installed the engine because I was hearing what sounded like light rod knock. I was told that the roller rockers were just louder than stock rockers and everything was fine. By 3K miles I had obvious rod knock and the shop owner informed me on the phone that there was no warranty since it was considered a "race build" so I tore it down myself. Turns out I had the "best your money can buy" aluminum heads that cracked. The manufacturer blamed the builder and said the heads were over torqued. The shop owner said he had followed the torque specs and I was left with a very expensive lesson. Since that experience I haven't let anyone touch any car I own. I will buy a manual or search the internet. I've made plenty of mistakes but I've learned from each of them. It's unfortunate but you can't take these cars to just any mechanic.