You can bend a cam or a crank. I addition to the ways Shurkey mentioned you can bend a cam just by leaving it sit in one spot with tension on the valve springs.How does one "bend" a cam or a crank? They are tempered steel, are they not?
My best guess here is that either the cam gears are heavily worn or they are not correct to begin with.
Uhm... I'll add this, though: We put timing sets on both of my Wife's POS's and they were TIGHT going on. Less then 1000 miles later, both chains have stretched and feel all dangly.
This is why if you have an engine sitting around for a long time you shpuld always back the rockers off untill they are loose.
You can bend a crank or a cam just by leaving them laying flat on the bench long enough.
Hardening or "Tempering" is more about making those surfaces machinable and wear resistant.
But it makes them more brittle.
The bending is caused by one side of the material being in compression while the opposite side is under tension.
One side is being pushed together while the side opposite is being pulled apart.
Thus, the bend.
There should be some slack on one side of the chain.
There is a spec for that.
But not loose enough to skip.
A couple of things come to mind.
Are you buying the same timing set from the same place over and over or are you trying different manufacturers?
It is quite possible these days to get into an entire run of bad parts.
Sometimes from different stores who use the same supplier but its just in a different box.
And sometimes just by a bad catalog number they keep selling the wrong part.
The only time ive ever had a similiar problem was decades ago on an aluminum 215 buick.
It had chewed its cam bearings to the point that I could move the cam up and down by hand.
Its a really odd problem to have on a SBC
Let us know what you find out