I have a 429scj in my 70 Torino. The engine was rebuilt in 93 and I believe we put in a Melling HV pump. My mechanical guage is fluctuating at rpm's over about 1800 and holds a constant pressure of around 50psi at rpm's below that. Is the HV pump causing this ? The pressure fluctuates between 30 and 50 psi. Thanks for any help!