Cooling issues, water pump question

Discussion in 'Troubleshooting & Diagnosis' started by brewquest, Sep 14, 2017.

  1. brewquest

    brewquest Member

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    0
    Jul 19, 2012
    Denver, Colorado
    Hey guys,

    This is a bit of a long shot here but I am wondering the diameter of a water pump pulley for a 73 Chevy SBC (Camaro, Vette)

    I am wondering because I can not keep my car under 200 degrees and after swapping in a march pulley kit I think the one I have is too big so it spins the impeller too slow.

    GM Engine Block number - 3970014

    Ive been chasing cooling issues for this car for a while now. If this isnt the fix Im thinking its internal to the motor.

    Things Ive tried

    • 3 new radiators. This newest one is a 3 row aluminum.
    • Different size electric fans with shrouds. The current setup is a pull fan with a shroud that covers about 90% of the radiator. Also, added a push fan on the other side, just for fun. They pull 18 amps
    • A remote transmission cooler
    • Wrapped headers
    • Advancing the timing, with vacuum advance. Currently at 34, up to 50 with advance
    • A/F ratio about 12.5 to 1
    • Flushing the system. Using a vacuum system to put new fluid in (several times)
    • Pulling the thermostat, also a 160 and a 180 temp
    • Filling the radiator on a hill, with the car jacked up to remove all bubbles
    • When I removed the original fan shroud with clutch I regret not keeping them. Im pretty sure the car ran hot then. I only added a thermostat by the headers afterward.
     
  2. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

    8,813
    133
    Nov 4, 2004
    Ringgold, GA
    Have you verified the sending unit and gauge? Are you getting hot enough to puke fluid out? You can use a non contact thermometer to give you a good idea. I seriously doubt it's an issue with the pulley since hundred of thousands are using the same size (stock) without over heating.
     
    budro6968 likes this.
  3. brewquest

    brewquest Member

    40
    0
    Jul 19, 2012
    Denver, Colorado
    I have used a infared thermometer to check temps of the block. It starts running like crap about 212 (boiling point of fuel) so I think its accurate. Its not puking fluid out. My current pulley from march is 6 1/4in dia. Im thinking of going to the junkyard and pulling something smaller.

    Checked on march performances website and they do sell high flow pulleys. Might be what I need, just pricey at $108

    http://marchperformance.com/chevy-s...ratio-6-rib-serpentine-water-pump-pulley.html
     
  4. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

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    Nov 4, 2004
    Ringgold, GA
    What water pump are you using?
     
  5. brewquest

    brewquest Member

    40
    0
    Jul 19, 2012
    Denver, Colorado
    Cheapo Auto zone pump, 40 bucks at the counter. Long
     
  6. brewquest

    brewquest Member

    40
    0
    Jul 19, 2012
    Denver, Colorado
    So now, I am wondering and struggling with the math. Currently I have a 6in crank shaft pulley, to a 2 3/4in alt pulley with a 6 1/4in water pump pulley. If I change that to a 7in crank pulley with the same 2 /34in alternator pulley and then a 5 1/4in pulley what kind of percentage increase on the flow at the water pump would that make? Holy math...
     
  7. 74BIBELOT

    74BIBELOT Veteran Member

    If you also replaced the crank pulley(small) that could be your problem, remember this pulley is the DRIVE pulley and the other ones are the DRiVEN pulleys, you are right on your math... keep thinking... lol!
    Regards
     
  8. 74BIBELOT

    74BIBELOT Veteran Member

    7.00 /6.25=1.12x1000rpm=1120
    6.00/6.250=0.96x1000 =960
    160 Rpm/turns less at 1000.
    Hope this make sense!
     
  9. brewquest

    brewquest Member

    40
    0
    Jul 19, 2012
    Denver, Colorado
    Ok, I'll take a shot

    Currently we have 6/6.25=.96

    Upgrade crank pulley 7/6.25=1.12
    1.12-.96=16% increase

    Upgrade wp pulley 6/5.25=1.14
    1.14-.96=18.2% increase in flow

    Upgrade both pulleys
    7/5.25=1.33
    1.33-.96=37% increase

    I just ordered both. This way I can start small and go bigger if there isnt enough change. Thanks guys!
     
  10. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

    8,813
    133
    Nov 4, 2004
    Ringgold, GA
    I'm betting that water pump is an open impeller type and the water is cavitating in the pump. You could pop it open and see if it has an anti cavitation plate attached to the impeller.
     

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