Torsion Bar Relief Valve Problems

[fwoody2000]

I am currently having problems with a torsion bar relief valve. In the past the valve has lifted light, chattered or had too long a blowdown. If the blowdown is adjusted the valve seems very sensitive to it, i.e. 5% setting change can result in the valve changing from 19% blowdown to almost no blowdown where the valve will simply simmer and not fully lift.
I am looking for any advice or past experience on what the problem could be?