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Hot Rods Why does my SB overheat/ run hot?

Discussion in 'The Hokey Ass Message Board' started by BaBa, Jul 9, 2021.

  1. BaBa
    Joined: Jun 2, 2011
    Posts: 114

    BaBa
    Member

    Thanks F-One those are good thoughts. I put manifolds on it from a mid 70's pickup. Always thought I should switch them out for headers because it might help the cooling but maybe that is the wrong way to go?
    I think after reviewing all the input I'll check the vac advance, check timing, check the gauge, see about relocating the AC condenser for better air flow and if that doesn't solve things, get a Zips adapter and go with a mechanical fan and shroud.
    You guys have pointed me in the right direction that I have an airflow problem since the overheating (if it is really overheating) is occurring at slower speeds. Wasn't a big problem when I lived on the central coast when temps were in the 70's-80's. A little more critical in AZ when it hits triple digits!
    Thanks again for all input!
     
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  2. Lloyd's paint & glass
    Joined: Nov 16, 2019
    Posts: 4,900

    Lloyd's paint & glass
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    I believe it's because the lower temp thermostat is staying open and not keeping the water in the radiator long enough to cool down.
     
    bchctybob and Desoto291Hemi like this.

  3. That what I have always stated... Running a "COOLER STAT" in AZ is NOT the trick. A 195 stat, slow down the water pump depending on your rear gears (could be spinning to fast), Let that coolant sit in that rad a few xtra seconds to cool down !

    MY OT DD was running 215-220 yesterday in stop and go, 195-210 in the summer with a SBC w/ac on in the summer get used to it...
     
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  4. anthony myrick
    Joined: Sep 4, 2009
    Posts: 8,117

    anthony myrick
    Member

    Sound good to me.
    It overheated parked. Ran warmer than I thought it should while driving but didn’t overheat.
    This same radiator was cooling a 352 fine. Swapped in the 302 and then had issues.
    Runs perfect with the hotter thermostat.
    Crazy stuff.
     
  5. Lloyd's paint & glass
    Joined: Nov 16, 2019
    Posts: 4,900

    Lloyd's paint & glass
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    I wondered myself if i should have put a 190-195 in mine
     
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  6. Budget36
    Joined: Nov 29, 2014
    Posts: 6,767

    Budget36
    Member

    Hmnn, if you are able to keep coolant in the radiator for a longer time period, wouldn’t it stand to reason the coolant would stay in the block longer and get even hotter?
    That’s what a TStat does, right? Stops coolant flow until it heats up enough to begin flowing.
     
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  7. Mr48chev
    Joined: Dec 28, 2007
    Posts: 29,597

    Mr48chev
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    My buddy had that going on with his Model A with a small block in it. His electric gauge was reading 268 but scaring me to death he could remove the radiator cap while it was running and it didn't even have the least bit of steam come out. With a temp probe the Walker radiator rep at the show showed us that the coolant was 3 degrees above the thermostat rating sitting there at an idle with a hot engine.

    Still if it is 100 + and the engine isn't overheating on the road with a load on it but the temp goes up at low speeds most likely it is due to air flow issues. First thing I would do is find the specs on that fan that is on the truck and see how much air flow it is actually rated at.
    I full and well understand the AD truck fan issue with engine swaps though. Most of the time a mechanical fan sits way too low on the radiator with an engine swap unless you have a small block with a Zips riser on it to raise the fan up where it needs to be. Even with my 250 six the fan sits way too low.
     
  8. BaBa
    Joined: Jun 2, 2011
    Posts: 114

    BaBa
    Member

    The fan is rated at 2500CFM It seems to move a lot of air. Just looked over the truck and the vac advance was plugged into the carb. It was a good 10 years between the time I junked the Camaro and when I finally got around to building Baba so I didn't remember where the various hoses went. Plugged into the manifold now.
     
  9. Jacksmith
    Joined: Sep 24, 2009
    Posts: 644

    Jacksmith
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    I run an aluminum hi-flow shorty water pump on my 327 in the '39. It's got a thick brass radiator on it and only a 4 blade steel fan with no shroud. The car does not over heat... in fact, I had to go to a 180 thermostat to get it to good operating temps. I believe the radiator and the pump are the reason. Air flow, fluid flow + cool.
     
    firstinsteele likes this.
  10. sdluck
    Joined: Sep 19, 2006
    Posts: 2,750

    sdluck
    Member

    Do you have a timing light?
     
  11. Blues4U
    Joined: Oct 1, 2015
    Posts: 5,701

    Blues4U
    Member
    from So Cal

    Sorry guys, but that's not how it works. Once the thermostat opens up, be it 180 or 195, it's open, and the coolant is flowing. Changing to a higher opening t-stat will not cause an engine to run cooler.

    Exactly, if the coolant is in the radiator longer, than it is also in the engine longer, getting hotter. It's simple logic.
     
  12. Lloyd's paint & glass
    Joined: Nov 16, 2019
    Posts: 4,900

    Lloyd's paint & glass
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    So take the thermostat out?
     
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  13. johnold1938
    Joined: Apr 19, 2009
    Posts: 409

    johnold1938
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    from indiana

    get rid of the electric temp senser !!
     
  14. Jacksmith
    Joined: Sep 24, 2009
    Posts: 644

    Jacksmith
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    Taking the t-stat out can, in some instances like on a long trip, cause the engine to over heat because it's not being cooled long enough in the radiator.
     
  15. Blues4U
    Joined: Oct 1, 2015
    Posts: 5,701

    Blues4U
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    from So Cal

    Then you defeat the purpose of the t-stat.
     
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  16. Guys, if the radiator is undersized or dirty inside and /or there is not adequate air flow through it, it gonna run 220 or better in the summer.... 160, 180, 195 stat, gutted stat , no stat, 1/2 , 3/4, 1 inch restrictor etc, probably not going to make a bit of difference,...in my experience.
     
  17. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 3,396

    2OLD2FAST
    Member
    from illinois

    Just so you know , there is no industry standard for measuring the CFM of an electric fan , those " ratings" are nothing More than advertising hype ! Remember in the 60's when stereo amps were rated "IPP" ( instant peak power) ? Another advertising hype BS Number
     
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  18. clem
    Joined: Dec 20, 2006
    Posts: 3,408

    clem
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    true, this is how I set my timing, on the side of the road on it’s first run, one hand on motor, other turning distributor, - amazing how quick the temperature changes !

    so has this resolved your problems ?
     
  19. anthony myrick
    Joined: Sep 4, 2009
    Posts: 8,117

    anthony myrick
    Member

    The 302 I had issues with the 180 thermostat ran hot on the way to work after I pulled the thermostat out once. I’ve had this 302 since high school. In my ignorance, I tried to fix a bad radiator by removing the thermostat.
    It went from running hot at idle to running hot driving.
     
  20. BaBa
    Joined: Jun 2, 2011
    Posts: 114

    BaBa
    Member

    BINGO!
    As mentioned above, it was a good 10 years between cannibalizing the Camaro and putting everything in Baba. I had hooked up the vacuum advance to the carb. Changed it to the manifold.
    So yesterday it was a balmy 107 so it was a good day to try the cooling system. Ran it in the shop for about 1/2 hour at idle and it stabilized at about 220. Took it out for a short cruise around the neighborhood with the AC cranked up full and it stayed at about 230. This is much better than previous when on a less stressful drive it would peg the gauge at 260. Problem solved.
    Now I have to figure out why my speedo quit working...
     
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  21. sdluck
    Joined: Sep 19, 2006
    Posts: 2,750

    sdluck
    Member

    Still never addressed the the dist timing.
     
    Last edited: Jul 12, 2021
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  22. jaracer
    Joined: Oct 4, 2008
    Posts: 1,114

    jaracer
    Member

    Back in the 70's Ford had a thermostatic valve on the thermostat housing that would switch the vacuum advance from ported to straight manifold vacuum. It was to help cool down the engine if it started running hot setting in traffic.
     
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  23. FrozenMerc
    Joined: Sep 4, 2009
    Posts: 2,736

    FrozenMerc
    Member

    Ahhh, the myth that is fan ratings. The question you need to answer is at what pressure drop is that 2500 CFM occurring. Chances are it is at a pressure drop the fan can not possibly produce with a radiator in front of it. Any Fan company that does not publish the Fan Performance Curve is not worth it's salt.

    From Spal (The only electric fan I would ever use).

    [​IMG]
     
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  24. Blues4U
    Joined: Oct 1, 2015
    Posts: 5,701

    Blues4U
    Member
    from So Cal

    Anecdote. On some forums they say "Cool story Bro". Way too many possible variables to try to draw much of a conclusion from it. The bottom line is, slowing the coolant down will not make it runn cooler, if anything it will do the opposite.

    I'm not savvy enough on the thermodynamic principles at play, I just know enough to be dangerous. But having read up on this subject many times, those engineers that are savvy in heat transfer have said repeatedly that slowing the coolant down will not improve cooling system performance. It has to do with temperature delta between engine and coolant, and between coolant and radiator, and the greater the delta T the greater the heat transfer efficiency, and so there is greater efficiency at the inlet of the radiator than at the outlet, so the faster you can get the coolant out of the engine and to the radiator the more efficiently the system will transfer heat from the coolant to the atmosphere.

    There is also the subject of laminar flow of the coolant through the radiator vs turbulent flow, and that turbulent flow is more efficient at transferring heat than laminar flow, and to get turbulent flow requires velocity. There is the Reynolds Equation for determining required velocity, anyone can google that for more information, but the bottom line is, slowing the rate of coolant flow has the opposite effect of what is desired in heat transfer.
     
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  25. anthony myrick
    Joined: Sep 4, 2009
    Posts: 8,117

    anthony myrick
    Member

    Never studied law


    ain’t no scientist either.
    But I do know what happened when I removed a t-stat. It ran hot. It ran hot with it. Just changed when it ran hot. Radiator was stopped up.
    I usually use the thermostat prescribed by the factory and let the radiator shop wizards do the math.
    My tractor hasn’t had a thermostat for about 10 years. No issues yet.
    Thermostat hung open on my 61. Took forever to warm up and didn’t run very well until it did.
    I guess every situation changes the variables.
     
    Last edited: Jul 12, 2021
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  26. Do you have the application for this shorter pump; sure would be handy.

    I came across a Corvette (?) pump with the 3/4" shaft in the past; but it wasn't shorter than a regular pump.
     
  27. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 3,396

    2OLD2FAST
    Member
    from illinois

    To the best of my knowledge , 5 5/8" & 7 1/4" are the only two sizes available for a gen 1 SBC , most are 5/8" shaft , a few corvettes had 3/4" shafts .
     
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  28. sdluck
    Joined: Sep 19, 2006
    Posts: 2,750

    sdluck
    Member

    Once again a guy doesn't want to fix his car or learn anything and can't use the search feature.Won't answer question and doesn't own a timing light.
     
    Tman likes this.
  29. anthony myrick
    Joined: Sep 4, 2009
    Posts: 8,117

    anthony myrick
    Member

    I’m old fashioned.
    I fit the engine with every thing on it with a radiator during the build.
    If the engine needs moved back then the cutoff wheels fire up. Spend a week worth of evenings moving my latest swap back 1 1/2.
    I have 2 inches clearance with a mechanical fan. Runs almost too cool.
    Worth every second it took
     
    Last edited: Jul 14, 2021
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  30. bchctybob
    Joined: Sep 18, 2011
    Posts: 3,094

    bchctybob
    ALLIANCE MEMBER

    Before you tear into anything I would get a mechanical temperature gauge and/or a laser thermometer (I have a Craftsman), do a little sanity check/calibration of the gauge with hot water and plug that into the place where your temp sender goes. Run the truck and see if your temp gauge is telling you the truth. I've found that electric temp gauges can vary significantly.
    While it's unlikely given the size of the engine compartment in those trucks, be sure that the hot air can get out easily. In my Chevy 350 powered Jaguar sedan the air was packing in at average road speeds. I formed two big louver-like outlets in the back of the inner fender panels and the running temp dropped to normal. With all the good radiator and fan stuff up front, I just wasn't exhausting enough air.
     
    Tman likes this.

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