I'm going to put a rebuilt engine in my 2004 Chevy.  How is Remanns?

Remanufactured engines are only as good as whoever remanufactured them.

A properly remanufactured engine is virtually as good as new: the entire engine is dismantled, all parts get checked against original specifications and are either machined or replaced to match the original specifications. The cleaned parts are then reassembled in the correct order and repainted as necessary.

It’s not a cheap process, and a properly remanufactured engine typically costs around half the price of a brand new one. But they also have the longest warranties: typically 12k miles or one year, whichever comes first.

Cheap remanufactured engines can be as bad as having a powerwash, oil and filter change, and then repainted. Those ones are a scam because they are just salvaged engines with shiny paint and often carry just a one month warranty with loads of get-out clauses.

There are legitimate cheaper alternatives which only rebuild the cylinder head after checking that the pistons and bores are in good order. They’re not guaranteed for as long as a fully remanufactured engine but are a lot cheaper.

For a 2004 Chevrolet you probably aren’t looking to spend much. If so, I’d just fit a good salvaged engine which has been seen running and has had an oil pressure check, and wet and dry compression tests. 

Many salvage yards don’t do any of that before resale, but they will give you a limited warranty of a few days to fit and check the lump if you ask before purchase, and will mark all the bolts and screws so that they can check you’ve not swapped or removed any parts. Those types of warranties are very limited: they won’t refund your fitting and removal costs, they won’t refund any delivery costs, and you have to pay to return the faulty lump to them and you have to pay for delivery of the replacement.

I always fit salvaged engines to a test stand and test them as I described and observe them starting and running *before* I attempt to fit them to the car. That also allows me to check for any oil leaks which may have been hidden if the supplier washed the outside of the engine before supplying it.

i would get a mechanic to help you out