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SBC running a little hot???

Discussion in 'The Hokey Ass Message Board' started by justice, Sep 23, 2003.

  1. justice
    Joined: Sep 12, 2003
    Posts: 110

    justice
    Member
    from Ohio

    Well, my engine is starting to run hot for some reason.
    It only has a few hundred miles on it.
    I have replaced the thermostat. I have an electric fan that is running fine, and the radiator was flow/pressure checked before I put it in.
    I have already replaced the manual guage and tested the new thermostat. All the air should naturally bleed up into the '51 radiator top tank (higher than the thermostat housing.)
    The water pump isn't leaking from the weep hole, but I guess it is next on the swap list.
    The engine has been holding 180 degrees parked or at speed since I built it. It started heating up only at highway speed lately, but now it stays hot when ya slow down too.
    I haven't had one do this to me before.
    Oh well, things that make you go, "Hmmmmm?"
    If you guys got any ideas, fire away.

    Justice
     
  2. Petejoe
    Joined: Nov 27, 2002
    Posts: 10,838

    Petejoe
    ALLIANCE MEMBER
    from Zoar, Ohio

    Well if you have adjusted the carbs or timing lately that may be the culprit. Too lean or too far advanced can cause overheating. I'd also flush the system again. Could be since the engine is newly rebuilt, something broke loose and doing some serious plugging. Good time to put in a high volume pump while your at it. A few things to look at.
     
  3. a/fxcomet
    Joined: Mar 31, 2001
    Posts: 554

    a/fxcomet
    Member
    from Eugene, OR

    Have you tried full manifold vacuum for the vac advance?
     
  4. How hot is hot? 180 is barely warm.With a pressure cap in traffic,220 shouldn't be a problem.Has it boiled over?
     

  5. Hey Justice,
    If you suck hot air from the engine compartment back thru the radiator you'll tend to run hot.

    Make sure you close off the sides, bottom, and space between the hood and top of the raditor so you can only suck fresh air in from the front outside of the car and you will notice a huge difference in temp.

    The stock sheet metal usually does a pretty good job of this - somtimes that gets discarded over time. Also get a fan with the most CFM that you can find.

    I put a 2750 cfm 16" fan on mine and it runs way cool - I have a 180 thermostat, but it often shows cooler than that on the gauge when crusing the highway - hope this helps - the sheetmetal did the trick for me - I recently got stuck in a 3 hour traffic jam and idled the entire time and never got over 190 or so - and it was hot. Pigeon Forge sucks.
     
  6. hudson_hawk
    Joined: Aug 27, 2002
    Posts: 647

    hudson_hawk
    Member

    i had my sensor mounted on the block and got new headers and it ran 20 drgees hotter until i moved it [​IMG]
     
  7. Deyomatic
    Joined: Apr 17, 2002
    Posts: 3,095

    Deyomatic
    Member
    from CT

    Is your lower hose collapsing? What happens is that the engine "sucks" the fulid so hard in some cases, that the hose collapses.
    Does your lower radiator hose have a spring in it to prevent collapsing? My 55 Fairlane has one, I almost took it out before someone told me what it was. I'd never seen one before.
    I've replaced MANY radiator hoses on SBCs through the years, and NONE of them have ever had a spring in the lower hose to prevent collapsing.
     
  8. crclebrner
    Joined: Nov 18, 2002
    Posts: 30

    crclebrner
    Member

    If all else fails, you may want to check for an internal combustion to coolant leak. What you described sounds like it could be a head gasket starting to blow or a crack in the head forming. Hopefully that's not the problem but, it is easy enough to check. Just take the thermastat housing and the belt that drives the water pump off and with the motor full of water till it's just about to run out of the thermastat hole in the intake, start her up for a few seconds. There should be no bubbles or water movement what-soever.
     
  9. justice
    Joined: Sep 12, 2003
    Posts: 110

    justice
    Member
    from Ohio

    Thanks for all of the suggestions! I always appreciate it when you guys take the time to put your ideas in writing.

    Let me see if I can clarify things a little for the benefit of you guys who are tryin' to help.

    The car has run fine since I built it. Nothing has been changed. It just started running hot out of nowhere lately.

    It cooled fine earlier in the summer when the temperature was in the nineties. It would hold right on the thermostat at 180 degrees, even in traffic.

    I would think any problems caused by design or capacity would have surfaced right off the bat.

    The bottom radiator hose does have a spring. The fan worked fine when it the weather was much hotter than it is now.
    ALl the engines I have built ran right on their thermostat.
    If they didn't, I upgraded components until they did.

    I hate an engine that runs hot!!

    Justice
     
  10. justice
    Joined: Sep 12, 2003
    Posts: 110

    justice
    Member
    from Ohio

    Aww man!!! i was afraid someone else might think that too. That is the one possibility I didn't want to consider.

    I was planning on checking that this evening, but I don't even like talking about it.

    I bought brand new heads for this engine, so I will be pi$$ed if they are already heading south on me.

    Justice
     
  11. justice
    Joined: Sep 12, 2003
    Posts: 110

    justice
    Member
    from Ohio

    One more thing to help you guys think.

    When it first started doing it at highway speeds, I would just floor it for a second. Sometimes this would cause the temperture to drop rapidly to the normal 180-ish degrees. After doing this a couple of times, it would settle down around the thermostat setting and wouldn't do it again for the remainder of the ride.

    Justice

     
  12. I dont want to ask a dumb question but have you spun the water pump by hand to see if it was free? My caddy started running hot, and when I tried to turn the pump it was real stiff. I changed the pump and the temp came down. Still runs at 195 though, damn caddy 500's!
     
  13. Deyomatic
    Joined: Apr 17, 2002
    Posts: 3,095

    Deyomatic
    Member
    from CT

    Caddychris, 195 ain't bad, try running from Phoenix to Tucson and back in July with the temp needle glued to 218.
     
  14. jerry
    Joined: Mar 2, 2001
    Posts: 3,473

    jerry
    Member

    make sure that you haven't lost the diaphram in the vacuum advance on the dist.

    especially on the low speed overheating.


    jerry
     
  15. Coming home from Billet Proof I was Runing about 215 But that still aint too bad. I stopped for a soda and when I started it up it was like 240 or so. Once I got on the road it cooled back down to 210-215. 500's come stock with a 195 t-stat.
     
  16. Sam F.
    Joined: Mar 28, 2002
    Posts: 4,225

    Sam F.
    BANNED

    after normal operating temps ,check upper and lower hose, are they both hot?(if so then your thremosta is opening) does radiator feel hot ,move your over the front of it,,it should feel warm in all areas.a cold spot will mean a clogged row. a fucked waterpump will usauly give you a tell tale sign of weeping or screching or just plain loose when you grab a hold of the shaft(shut of of course)

    other than that timing can also be an issue and cause overheating or maybe even a misadjusted carb,but very rarley....good luck
     
  17. justice
    Joined: Sep 12, 2003
    Posts: 110

    justice
    Member
    from Ohio

    Caddy,

    Don't worry about sounding dumb. Heck I got more skin than that!
    Yep, the water pump turns OK without the belt.
    I think I found the problem last night. The short version is: bad thermostat & bad manual guage.
    Long version:
    It ran hot, so I swapped the thermostat for another one I had in my parts stash. It still ran hot, so I suspected my guage. I replaced the guage, and it still ran hot.
    I then suspected that the stat I got out of my parts cabinet might have been a bad one that I neglected to throw away.
    I took the original 180 stat and the 195 I replaced it with and tested them both on the stove.
    The 195 appeared to be bad. It didn't open up at all until well over 200 degrees. It never opened near as wide as the 180.
    This evening I'll put the 180 back in with some fresh anti-freeze/water and see what happens.
    Stay tuned for the outcome....lol

    Justice
     
  18. justice
    Joined: Sep 12, 2003
    Posts: 110

    justice
    Member
    from Ohio

    I'll have to check that this evening if I still have trouble with it.
    That is a good suggestion!! Thanks

    The distributor and vacuum advance are new, so hopefully that isn't the cause. However, we have all seen new parts fail.

    Justice
     
  19. smokindave
    Joined: May 30, 2005
    Posts: 391

    smokindave
    Member

    I found this old post here, so I didn't want to starty a new one. I have a newly rebuilt 350 in my '51 and it is running close to 210 with a 190 thermostat in it. From what I have read here and on other posts, this is OK. Am I right. I run a stock fan with a shroud and it has never boiled over. what temp would be a point of concern? the motor has been bored, and is around a 355. Any help would be appreciated.
     
  20. Hank
    Joined: Feb 18, 2005
    Posts: 234

    Hank
    Member
    from Wisconsin

    Have you checked the timing lately? It may have moved.
     
  21. MR.BROWN
    Joined: Apr 15, 2010
    Posts: 25

    MR.BROWN
    Member

    Make sure the lower hose has the spring in it. They rarely come with them new anymore.
     
  22. smokindave
    Joined: May 30, 2005
    Posts: 391

    smokindave
    Member

    The lower hose has a spring in it. The radiator is clean, I am just concerned that 210 is excessive. I am not looking forward to the summer if it is running that hot.
     
  23. Mr48chev
    Joined: Dec 28, 2007
    Posts: 28,779

    Mr48chev
    ALLIANCE MEMBER

    +1 Is it puking coolant when you drive? What thermostat do you have?

    210 is 2 degrees below the boiling point of water in a pan on the stove so it isn't hot as far as a small block goes under normal driving conditions. The 79 350 in my ot truck runs a 195 thermostat as standard equipment.

    If you have an electric gauge it probably isn't all that accurate anyhow from my experience.

    You may have a few bugs or other stuff in the radiator but it may also be that the outside temperature where you live is going up a bit now and the engine is going to run a few degrees warmer because of that. Unless it pukes coolant or acts up otherwise it isn't a problem.
    I checked and the outside temp in your area is in the low 80's and that shouldn't be enough to cause any issues with heating problems.

    If you aren't running a thermostat it may be that the coolant isn't getting enough time to cool the engine down like it should because it is flowing through it too fast but it shouldn't be that hot outside here in the states yet for that to cause a problem.
     
    Last edited: May 5, 2010
  24. walker
    Joined: Dec 29, 2008
    Posts: 217

    walker
    Member

    Be sure to check the temp with an actual thermometer, not just the gauge.
     
  25. knotheads
    Joined: Jan 4, 2007
    Posts: 499

    knotheads
    Member

    another thing to check on the sbc is water pump impeller. the sheetmetal impeller vains flair out and change shape after some use and reduce the pumping action. there used to be a plate you could buy and pop rivet on the back side of the impeller to prevent this.
     
  26. smokindave
    Joined: May 30, 2005
    Posts: 391

    smokindave
    Member

    Thanks for the replies. Everything on the car has been gone through (motor wise) or is new (water pump). The only thing I didn't have done was the heads, just because I ran out of money, and the heads can be removed with the motor in the car. It came down to time and money. My biggest fear is just overheating going over the Grapevine this summer.
     
  27. 32SEDAN
    Joined: Jul 30, 2008
    Posts: 1,295

    32SEDAN
    Member

    Could be an air bubble?
     

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