Not to steal this thread, but I once built an engine for a friends 63 pickup. Budget build .030 over valve job on stock heads, new pistons, RV cam, lifters, rings, bearings etc. I was putting it together when he showed up with a box of garage sale parts - polished early finned aluminum heads, chrome front cover and a really cool aluminum scoop that had operating butterflies to look like unit off a blower motor.
All good and then he brings out this polished water pump. I couldn't put my finger on it but it looked somehow not right to me.
Long story short, finished up with some used Hooker headers that I had cleaned up and coated with VHT (charged him 50 bucks - and I paid 10 at a swap meet!) and cherry bombs, clamp on exhaust pipe out the back and I shoved on little chrome tips from a sink trap - fired right up, sounded great and after a couple hundred miles he changed the oil and it was clear as honey. New oil, new filter and he was off on a weekend trip several hundred miles away.
Got a call several hours later and he told me, "That #$%^& engine you built for me just crapped out!" He was not happy (nor was I as I drove out to pick him up.) Couldn't tell much in the dark but I did manage to tow him home (he didn't say a word for sixty miles) and told him we needed to wait until we both cooled off a bit before saying anything more or pointing fingers. Next morning the damage was assessed - water pump shaft broke, pump seized causing belts to fry, fan went into the radiator and made a real mess.
Had the radiator rebuilt, put on a new out-of-the-box rebuilt GM water pump (that I painted and in my shop). The friendship was a good one and we got things all talked out - he paid for the radiator, antifreeze and new belts - I gave him the pump and wouldn't take anything for my time.
We both learned a big lesson - he learned that I really did know my stuff about engines (ran that truck for ten more years and sold it with that engine still in it) and I learned to say, "No!" when it comes to parts that I have not bought or at least vetted.
Bit of a rant, but I'm real sure others here can say, "Oh man, I had the same kind of thing happen too!"
Regards All,
Glenn