Stock 350 Operating Temp

Discussion in 'Small Block Tech' started by Rich Skylark, Jul 29, 2020.

  1. Rich Skylark

    Rich Skylark Gold Level Contributor

    My 68 stock original is running on the warm side the last few weeks since emerging from hibernation the last few weeks . Last few weeks have been typical summer temperatures with an abundance of humidity, the car is running 195- 215 sitting in traffic. Bringing up the RPM’s will drops the temp 10-15 degrees.’ On the hwy and at night the temp is in the -80-190 range . I flushed the radiator ( with water ) 6 weeks ago to get the old antifreeze out and put in new thermostat ( 160 ) . Anything else I’m overlooking Water pump changed 5 yrs ago as well as radiator boiled out at that time . Car sat for. 3 + yrs and I’m remembering 185 degrees as the ceiling .
     
  2. Eric

    Eric Founders Club Member

    Wait for Larry the Wizard's response on here and follow his instructions to the T!
    He helped me figure out my high temp problem and I have never looked back. He's a great guy and knows his stuff!
     
  3. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Rich,
    Lots of guys have problems with their cooling system losing control of engine temperature. That is what is happening in your case. The thermostat sets the operating temperature of the system. If everything is up to snuff, the temperature should never exceed the thermostat rating by more than 5-10*. The stat begins to open at it's rated temperature. It is fully open about 20* above that rated temp. Normally, the thermostat will open and close to varying amounts as it tries to keep the temperature at which it is rated. Once it is fully open, allowing the maximum amount of coolant to enter the radiator, and the temperature continues to rise, it has lost all control.

    The biggest problem in most cases is guys wanting to stick with their old radiators. I don't care what you do to an old radiator, flush, boil, whatever, all you'll have is a old, at least partially clogged radiator. Brass copper radiators get clogged by solder bloom. Solder bloom is a reaction between the coolant and the solder used in those radiators. It looks like white scale inside the radiator. There is a reason all new cars use aluminum radiators. They are better. Aluminum is not as good a conductor of heat as brass/copper, but it is stiffer, so the tube sizes in an aluminum radiator can be up to 1 1/2". Brass/copper being soft limits tube sizes to about 5/8" max. A 2 row aluminum radiator with 1" tubes is all most engines will ever need. Before buying an aluminum radiator, ALWAYS check the tube size. 1" minimum is what you want, and 2 rows maximum. If you see a 3 or 4 row aluminum radiator, don't waste your money.

    Assuming you have the right fan shroud and good clutch fan, the next thing is ignition timing. Retarded ignition timing causes more heat from the combustion process to go into the cooling system instead of pushing the piston down. The 68 and 69 cars were commonly initially timed at 0* (TDC). Vacuum advance was connected to manifold vacuum, so it was always there, boosting that timing by 14-18*, even at idle. At cruise, it would supplement the mechanical advance so the timing was in the mid to high 30's, if not 40*. That helped the engine to run cooler. Unfortunately, ignition timing seems to be one of the most misunderstood topics for lots of guys. All they know is initial timing. That is where it begins and ends for them. It matters what the timing is at idle, as well as going down the road at 60 MPH. You need to check the vacuum advance. It may not be working.

    The main purpose of anti freeze is in it's name, freeze protection, and corrosion protection as well. Ethylene Glycol does not transfer heat as well as good old water. The more you use, the worse your heat transfer is. That is why the back of the container says no more than 70%. Less is better, especially in the summer. 100% water is best, but you do need freeze protection in the winter depending on your location, and corrosion protection is important as well. Products like Red Line Water Wetter let you use 100% water or less anti freeze if you want, yet provide the corrosion protection.
     
    Last edited: Jul 29, 2020
    Dwayne B and MrSony like this.
  4. 1987Regal

    1987Regal Well-Known Member

    X2 on tube size, I over looked my old when I bought it. It was a champion 2 row with 3/4 wide tubes. It doesn't sound like much but across-the-board that's a lot you're losing a half inch of cooling per row. And you might be chasing an issue you thought you took care of. 2 nd and final radiator is a northern brand.
    Josh
     
  5. alec296

    alec296 i need another buick

    Sounds like you need a little more air flow. It may be fan clutch is weak, or radiator is starting to plug. Or even timing may be low, vacuum advance weak.
    check timing at idle with and without vacuum advance. Start there. 215 is not actually hot yet, modern cars run that for emissions. But can be a sign of something going out.
    Boiling out radiator 5 years ago, and if it’s not a daily driver, it can be plugged already.
     
  6. Rich Skylark

    Rich Skylark Gold Level Contributor

    Thanks for the info guys, a lot info to go over . The radiator seems to be a good move to make . Timing on my car is questionable due to timing chain due for a replacement. Will keep you updated.
     
  7. Rich Skylark

    Rich Skylark Gold Level Contributor

    First things first ,
    the fan clutch is shot, new one on the way. What’s the most direct method for checking vacuum advance function?
     
  8. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    The VA should be hooked to manifold vacuum. When you unhook the hose with the engine running, it should hiss, and if you have a timing light hooked up, you should see the timing mark move at least an inch or so. The idle will slow noticeably when you unhook the hose if everything is working.
     
    Rich Skylark likes this.
  9. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    I could have easily checked it for you tonight.:D Before we got kicked out of course.
     
  10. Mark Demko

    Mark Demko Well-Known Member

    Go for a new radiator, even when I was a preteen, I remember my dad had the radiator in his 75 LeSabre “fixed” it was boiled or soldered or something, it didn’t work for long.
     
  11. Rich Skylark

    Rich Skylark Gold Level Contributor

    I’m looking at it now b4 it gets too hot .with the advance disconnected The timing mark is showing up approx 1/2” below ( off the mark ) . Moving it back to the center of the tab “ 0 “ my idle increased 250 RPM’s . Going for a short hop locally to see I can detect a difference
     

    Attached Files:

  12. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    I'll say it one more time. With the timing light attached, engine at idle, disconnecting the vacuum advance should move the mark, and cause the engine idle to drop. There should be strong suction at the disconnected hose.
     
  13. Rich Skylark

    Rich Skylark Gold Level Contributor

    Disconnecting the vacuum advance at idle didn’t have any effect on the mark or lower Rpm’s . I timed it by ear , and a few test drives - not the most scientific but yielded some positive results . Suprisingly the car runs noticeably better with the timing mark at the top line on the mark. The service manual says 15 if I’m reading it correctly . The idle went up 250 rpm’s which I corrected on the carb . By way of digital tach I’m at 640 in park and 520 rpms in gear . Driving around town stop and go the car runs smooth as it always did but way more pick up and no pinging heard . This is with 89 octane gas . Also for the entire cruise the car didn’t go above 185 degrees. Still going to change the V Advance and see what that yields . Any other thoughts anyone might have keep them coming !
     
  14. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    When you disconnected the vacuum advance line, did it hiss, was there suction?

    BTW, you just did what I explicitly tell guys NOT to do, adjust the initial timing without any regard for the total advance.
     
    Last edited: Aug 1, 2020
  15. Rich Skylark

    Rich Skylark Gold Level Contributor

    No hissing no suction , strange ; I have a new vacuum advance , would installing that be my next step ?
     
  16. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    You have the hose hooked to the wrong port on the carburetor. Hook it to a port that hisses, that's manifold vacuum. Your VA might be fine.
     
  17. 1987Regal

    1987Regal Well-Known Member

    Put a vacuum gauge on it, I wonder if you got something else going on. You should have some hissing, suction, rpm difference. A new vacuum advance will not fix it if don't have vacuum
     
  18. Rich Skylark

    Rich Skylark Gold Level Contributor

    The other day I put a vacuum gauge on the vacuum advance , pumped it up, and highest # I can get was 15 lbs . At that point the VA couldn’t hold that pressure and began to leak down Am I correct in that my VA is no good & needs to be replaced ? Also discovered my thermovacuume switch is functional- I had the hoses in the wrong order .
    When disconnecting hose from the VA plenty of suction and idle does slow.
    As I said in my previous post ,’since advancing the time to 2degrees ,car seems to be running a little smoother and definitely is noticeably quicker with more pull & no detectable detonation. After I install the new VA I have to check the total timing advance . Also interesting is car is running cooler in this heat , around 180-185’max . An aluminum radiator is in the near future and verified I have the correct shroud .
     

Share This Page