Radiator Cap Pressure for GS400

Discussion in 'Street/strip 400/430/455' started by Patent Pending, Sep 4, 2016.

  1. Patent Pending

    Patent Pending Well-Known Member

    My existing cooling system has a 13' cap and has been running a bit hotter than I'd like here in S. Florida (215-220). Radiator started oozing a bit too from the core, so it's time to replace/upgrade. Just ordered a new aluminum radiator, new hoses and 180 thermostat. I've searched the forum and didn't find anything relating to the proper radiator cap. Service manual says 14-17'. Should I stick with 13' or replace with 16'?
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    I think the AC Delco cap is 15 psi, but 13, 14, 15, 16 psi cap will work just fine. I don't think it really makes much difference. The reason for keeping the cooling system pressurized is to elevate the boiling point. I think you'll find most are 16 psi.
  3. shiftbyear

    shiftbyear Well-Known Member

    Alan, for every pound of pressure provided by the cap, the boiling point is raised 3 degrees at sea level. So a 15# cap will increase the boiling point of pure water 45 degrees. Other things to consider, maybe a high flow thermostat and high flow water pump. Check internet for proper coolant bleeding procedures. Last but not least, make sure your engine grounds are good, believe it or not if the grounds aren't good, electrolysis may cause current to flow through your coolant looking for a ground. Good luck
  4. Schurkey

    Schurkey Silver Level contributor

    Pressurized cooling system makes the water pump more efficient, too. More pressure is good--as long as you aren't over-pressurizing hoses, gaskets, seals, etc.
  5. Patent Pending

    Patent Pending Well-Known Member

    Thanks all. Good advice all around.

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