Engine valves aren't soldered or even welded; they're replaced. You seem
to believe that this is a small repair - like a leaky radiator - it's
not - it's a big, costly mess. That's why the car was so cheap.
Here's what will be needed - more or less:
New timing chain(s)
New cylinderhead gasket
New valve cover gasket
New coolant
Oil change and filter
New camshaft
Some new camshaft bearings
Some new valves
Some new valve guides
Some new rocker arms
New valve stem seals
Alternatively, a used cylinderhead from a wrecked car would be a
substitute for the last six parts plus the labor to install those parts
on your car's cylinderhead. The chains and gaskets etc. are required in
either case as is the shop labor to remove and replace the cylinder head
and timing chain.
At the end of all this pain you'll hopefully have a running engine -
then the question becomes: What about the rest of the car? What else
needs to be fixed so that it's roadworthy?????
If you have limited time and limited $$ the best alternative might be to
sell this hulk, for that's what it is, and move on to something that's
running and can be driven now.
Final thought. A local community college may have an auto shop class
that might be interested in using this job as instruction for its
students. That means weeks, not days, to repair it; the labor is free
but not the parts.
Hope this puts the situation into focus.
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