Running hot

Discussion in 'Small Block Tech' started by Brad W, Sep 22, 2018.

  1. Brad W

    Brad W Miles from nowhere...

    I was adjusting my idle mixture screws on the '72 350-4 today and after I got them set I took the car for a test drive. The car ran great except for some slight pinging under heave acceleration. I have the car pwoer timed but I think I need to back off the timing a little.

    Anyway, during the test drive I noticed my gage was above 190 which I've never seen this car do, I headed back when I was seeing 195 I was excepting to see the temp drop but it acted like the thermostat wasn't opening.

    When I got home the temp was pushing 200 but not over, whe I turned the motor off and open the hood everything look good but when I tried to squeeze the upper radiator hose it was hard as a rock. I replaced the thermostat about a year ago with a 185 and never had a problem with over heating until today.

    I don't remember the name or quality of the thermostat I stuck in there. Could it be the that it went bad so soon? I'm thinking the first thing I should do is replace the thermostat and see what happens then go from there.

    If anybody has any suggestions I'd like to hear them.


  2. BuickV8Mike

    BuickV8Mike SD Buick Fan

    Make sure the vacuum advance is working. Lean carb will also make it run hotter. What fan do you have? Flex fans run cooler. Straight water helps.
  3. Brad W

    Brad W Miles from nowhere...

    I didn't know a lean carb will make an engine run hotter. I wonder if when I readjusted the mixture screws I made it to lean? The problem did start right after I adjusted the carb. I thought I did it correctly. I started with the screws out 2 turns out from close, then turned the screws in until the rpms dropped about 50 rpms then I turned the out 1/4 turn. Engine seams to run ok but maybe like you said I'm running too lean.

    I did change the thermostat but have not run the engine. I'll see what happens tomorrow and if that doesn't fix it I recheck the mixture screws. I'f the doesn't help I'll redo the dewell and timing.

    Thanks Mike!

  4. TrunkMonkey

    TrunkMonkey Well-Known Member

    The mixture screws only meter air flow at idle. They do not meter fuel.

    If all you did was change the idle, you might be lean at idle and the car could run hotter at idle or in traffic, but that should not change the off idle, driving/cruising at RPM over 1500 or so.

    Chasing a problem like this after making a change by changing something else, can be a long journey back to undoing what you last changed.

    Whenever possible, "go back to zero", undo what you did and put the car back to the state it was before you had this problem. Then make one change at a time and get the results, before you change another thing.

    Sometimes situations arise that you cannot do this, but when you can, it will almost always be the easier path, and less frustrating.

    Since it was carburation you adjusted, check your vacuum lines and the carb linkages to make sure there are no vacuum leaks, and then fast choke, and no linkages are bent or binding.

    And in order.

    Correct timing. Timing is (almost) everything.
    Then make sure vacuum is solid, no leaks.
    After that, you can start with carb adjustments. (given that the carb has a good baseline so the car will run.)

    Hope that helps.
  5. Marv Marksberry

    Marv Marksberry Well-Known Member

    Just an FYI,
    Water turns into steam at 212°F. Mixing traditional ethylene glycol antifreeze with water in a 50-50 ratio increases the boiling point to 223°F, which is close to the operating temperature of an engine. ... The high boiling point ensures that the coolant remains liquid at all times, enabling consistently effective cooling.

  6. BuickV8Mike

    BuickV8Mike SD Buick Fan

  7. alec296

    alec296 i need another buick

    Only 2 turns out is pretty lean , I would suggest a vacuum gauge and tune for higher vacuum. But idle mixture doesn’t affect wide open. That may be timing too high . Heat creates pressure so the hose being under pressure after a drive is normal. I would back down timing 2 degrees at a time until it does not ping.
  8. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Yes, but the cooling system operates under pressure, 14-16 psi. That alone raises the boiling point of 100% water to 250*. Ethylene Glycol actually decreases heat transfer, which is why they tell you on the back of the container to not use over 70% A/F. The less you use, the better, unless you need the freeze protection. Distilled water plus Red Line Water Wetter gives you the maximum heat transfer plus corrosion protection.
  9. Brad W

    Brad W Miles from nowhere...

    The car had a/c which i removed so it has the 7 blade fan. I'm running 50/50 a/f and water.
  10. Brad W

    Brad W Miles from nowhere...

    Thanks for the help Michael, so I recheck everything and I did not have the vac line to the advance hooked up when I did my test drive! So I hooked the vac line back up then backed the mixture screws out 1/4 quarter turn then went for a test drive. No over heating and no pinging! thant made me feel good

    But I think what I'm going to do my next day off is to is to reset the dwell, re do the timing and then readjust the carb. that way I'll know where everthing is. I changed the points and condenser about 6 months ago so I'm sure there're ok.

    TrunkMonkey likes this.
  11. TrunkMonkey

    TrunkMonkey Well-Known Member

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