I'm sure glad I didn't spend Money on replacing my front heating core.  I
hear it's spendy having a machanic put one in. All I really needed was a
simple engine rebuild to relieve the back pressure from my cooling system.
The pressure thing tends to happen when you have cracked heads.  So now that
the heads have been replaced 3 times in the last 4 years.  I deceided to
overhaul the bottom end by a very specialized machine shop.  The heater now
blows hotter than I ever expected.  All for the small price of $2800 after
taxes.
Now the PROBLEM.
When the engine is at idle for about 5 to 10 minutes, it starts getting real
uneven, starts sputtering and stalls.  Is it the O2 sensor?.