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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. sdluck
    Joined: Sep 19, 2006
    Posts: 2,750


    Keeps saying the timing set correctly but you don't tell us where it's at
  2. Do you have space between the condenser and radiator? If so, how much?
  3. chop&drop
    Joined: Oct 11, 2006
    Posts: 452


    I’m with “olscrounger”. I’m running a 350 SBC in my roadster with a Walker and Cooling Components fan and shroud. Never runs hot here in Texas.
    Lil32 and olscrounger like this.
  4. BaBa
    Joined: Jun 2, 2011
    Posts: 114


    Can't recall the timing setting I can look it up in the Camaro shop manual, if it runs hot and I set the timing a few degrees closer to TDC that should make it run cooler right?
    Not much space between the rad and condenser, maybe 1/2 inch? I have lots of room behind the grill so I can set it farther forward by fabricating some brackets.
    Desoto291Hemi likes this.
  5. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 27,016

    Jalopy Joker

  6. Mr48chev
    Joined: Dec 28, 2007
    Posts: 29,567


    74 Camaro thermostat .png I can never figure out why you guys piss all over your shoes over an engine running 200 degrees after you put it in an old vehicle when that same damned engine ran over 200 all the time in the vehicle it came in without and issue. 200 isn't hot for a 350. Puking coolant on the ground in traffic is hot for a 350. You don't have a 216 in it anymore sodon't react like it was a 216.
    From the 74 Camaro 350 thermostat listing on Rock Auto. Standard temp thermostat for a 74 Camaro is 195 and if that engine is running at 195/200 it is running at the normal operating temp for the Camaro it came out of.
    Last edited: Jul 9, 2021
    kevinrevin, jaracer, brianf31 and 4 others like this.
  7. BaBa
    Joined: Jun 2, 2011
    Posts: 114


    bchctybob likes this.
  8. Budget36
    Joined: Nov 29, 2014
    Posts: 6,739


    Anyone catch the part “when the gauge pegs it doesn’t boil over” or similar.

    Based on that statement I retract my earlier post;)
    firstinsteele likes this.
  9. Rand Man
    Joined: Aug 23, 2004
    Posts: 3,965

    Rand Man

    I like mechanical fans, and electric for backup only. Take one look at any stock fan blade and you can tell it moves more air than the electric. Fans are my business, but I’m not going to bore you with with formulas about pitch, diameter, etc.
    HotRod33, bchctybob, jim snow and 2 others like this.
  10. squirrel
    Joined: Sep 23, 2004
    Posts: 49,276


    Retarding timing will make it run warmer....but having it too far advanced can make it run warmer, too. It wants to be right. Sometimes playing with vacuum advance, to make it come on at idle, can help with idling temps, according to some folks. Never done much for me.
  11. jimmy six
    Joined: Mar 21, 2006
    Posts: 9,470

    jimmy six

    Jalopy Joe’s photo is what’s needed if your going to use an electric fan. Your only sucking air with yours system at about 60% of your radiators surface. A lot here find Lincoln electric Stock fans they really move air. There are really neat aluminum shrouds for almost any size radiator body in Summit, Jegs, Speedway for circle track. I’ve used 2 of them. One I turned vertical. You cut the hole after you find center on your water pump. Both use mechanical fans..
    One last thing that my car needed was a seal over the radiator and it’s mount to the hood. Then all the air is forced thru the radiator and condenser. Its made from light weight steel but aluminum would do. I bought a clip on seal with collapsible rubber from Mc Master Carr that fits on the metal. It really made a difference.
    One last thing, how’s your overflow? I start with 1” of coolant cold band mines full when I’m at 205 stuck in traffic. What’s your cap 15…20….25? 89009C9B-6428-400D-ACD7-5E2C72E03DCB.jpeg EF88786A-DEC3-4D51-B635-9E862AC2A57D.jpeg
    Last edited: Jul 9, 2021
    Sunday driver and norms30a like this.
  12. sdluck
    Joined: Sep 19, 2006
    Posts: 2,750


    What if the balancer shifted or wrong one or wrong year,time it with a vacuum gauge.Motor is no longer stock or in a smog car. Chevy had at least 4 different balancer and timing covers.
  13. SlamIam
    Joined: Oct 8, 2007
    Posts: 448


    Please forgive me if this is a stupid suggestion, but is the fan turning the correct way to pull air through the radiator? Have seen them hooked up with the wrong polarity
  14. blue 49
    Joined: Dec 24, 2006
    Posts: 1,408

    blue 49
    from Iowa

    '49 engine.jpg
    Your set up is very much like the one I did 30 yrs ago except mine has a brass radiator (a crossflow stood upright) and a mechanical flex fan (probably from a AC equipped AMC car). Mine worked out well and didn't get hot at all idling around GoodGuys-Des Moines in 90+ degree heat.

    bchctybob and Elcohaulic like this.
  15. If you were driving a '74 Camaro would you worry about it running 200*? Probably not.
    Definitely move the condenser. You can improve things by installing a shroud that covers the entire radiator (with the fan moved back a bit).
    What shape is the block in? Any rust? Try a THOROUGH flush and run a water/anti freeze mix (I've never seen a huge benefit to the 'water wetter' stuff. YMMV
  16. Had a similar issue with the 350 in the 49 Merc. It would run hot at idle and diesel when shut off. one day i noticed the vacuum advance hose. It was connected to the carb. I moved it to the manifold and that solved the issue.
    Rand Man likes this.
  17. Fabulous50's
    Joined: Nov 18, 2017
    Posts: 322

    from Maine

    I'll speak to the 4 row radiator:

    More rows in the same thickness radiator means less cooling and more resistance to airflow. A typical 3" thick aluminum radiator with two 1" rows has more surface area than the same 3" thick rad with four 1/2" rows.

    To the electric fan:
    A shallow fan has to spin very fast to achieve its rated CFM airflow. A fast spinning shallow fan has very little pull through a restrictive 4 row radiator. You need depth to get air velocity.

    anthony myrick, joel and SEAAIRE354 like this.
  18. BaBa
    Joined: Jun 2, 2011
    Posts: 114


    Thanks to all for the feedback. I'm going to print this whole thread out and work through the issues step by step (starting with the cheapest/easiest of course) when the weather cools down and I can spend some time in the shop. I knew the HAMB brain trust would come through.
    Thanks again!
    cactus1 and lothiandon1940 like this.
  19. David Gersic
    Joined: Feb 15, 2015
    Posts: 2,398

    David Gersic
    from DeKalb, IL

    I have pretty much the same engine, 37 Chevy so less grill area than you’re working with. Spal fan, because it fits.

    If you need more room, changing the water pump may help. There are long, short, and “Corvette short” pumps. The ‘vette pump will gain you about 1/2” over a standard short pump.

    Airflow through the radiator is one key. A shroud helps the fan pull more air through the radiator at low speed. Depending on the CFM your fan moves, the shroud could obstruct air at speed. Are you running hot at idle, or on the highway? Does the air have a good exit from under the hood?

    Overflow tank in use? Is it filling and emptying correctly? Or overflowing?

    Check (or replace) your radiator cap. Mine wasn’t holding full rated pressure. It never boiled over, but it did allow some bubbles to form. This raised the system temperature as seen on the gauge. With a new cap, I run 200F all day. But, I’m in northern Illinois, not Arizona.
  20. norms30a
    Joined: Jul 17, 2008
    Posts: 574


    Read Jimmy Six carefully, lots of info there. I have a Lincoln Mark 8 fan from a 1998 Lincoln and it has 7 very aggressive blades and is built into a shroud which fits my 55 Chevy pickup radiator about perfectly. I got mine from a guy on E bay. You can see pictures of them by going to e bay. Mine is variable rate speed-2 wire.
    olscrounger likes this.
  21. Looking at this photo, it looks like you could use a larger fan, and make sure it's pulling, it's easy to wire them up backwards HRP

    lonejacklarry and BigDogSS like this.
  22. I wonder if living in Arizona a engine driven fan along with a shroud may be a better set up, adding a zips riser you can raise the water pump up 5" to center a large metal fan in the middle of the radiator. HRP
  23. Tman
    Joined: Mar 2, 2001
    Posts: 34,448


    Spot on. I was thinking the same thing. Also, agree with making sure the gauge actually is correct.
  24. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 3,385

    from illinois

    If the " corvette" pump is shorter , where do you access pulleys for it ?
  25. anthony myrick
    Joined: Sep 4, 2009
    Posts: 8,112

    anthony myrick

    I had a 302 ford run hot after an install. I bought a 180 thermostat during the build and installed it. Looked up the factory thermostat. Originally it was a 190. Installed the190 thermostat and no boiling over.
    I really don’t know why. The 180 wasn’t stuck or non functional.
    The 350 I’m running now lives in the 210-215 range all day. No issues other than the occasional vapor lock.
    I recently installed a 500. Used a radiator built by Brice Thomas. Their scientists did the math for engine size, HP range and vehicle weight. (7500#)
    The radiator is aluminum with an industrial, large 2 row core. This aluminum one weighs almost as much as the copper one it replaced. The 500 runs 20 degrees cooler than the 350 did.
    Mechanical fan. No shroud.
    Tman likes this.
  26. David Gersic
    Joined: Feb 15, 2015
    Posts: 2,398

    David Gersic
    from DeKalb, IL

    The pulley goes on the shaft, like any SBC, but the shaft is also a different diameter.
  27. 200 with A/C, in July, in the Valley of the Sun? What's the problem?
    BigDogSS and Tman like this.
  28. The 39 guy
    Joined: Nov 5, 2010
    Posts: 3,054

    The 39 guy

    BUBBAS Truck.jpg
    So this avatar of yours is pretty fuzzy Ba Ba but it looks like you might have some extra bumper blocking your grill area. I had one of these chevy trucks set up similar to yours and I never did really get it to run cool on a warm day. It seems that the front end of this body style is just not real good at getting fresh air in and hot air out. So if you have anything in front of the grill I would recommend you get it out of the way. If your truck is real low to the ground that
    I think that also contributes to a lack of air flow through the engine bay. Hope you get it sorted out so you can enjoy your truck.
    bchctybob, Tman, impala4speed and 2 others like this.
  29. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 3,385

    from illinois

  30. F-ONE
    Joined: Mar 27, 2008
    Posts: 2,828

    from Alabama

    Reading through....
    It runs about 200 degrees, correct?
    It will go hotter than that, correct? You said you stopped and let it cool.
    So when that happened, how hot did it get?
    How did it do with the original 3100 radiator? The same? Was there improvement with new set up?
    Are you running headers or manifolds?

    My thoughts....
    What's the history of the engine? 1974? Could it be a 400?
    400s can run hot especially if the wrong head gaskets are used. I would double check the block numbers.
    400s can also run hot if overbored....they all can.
    I recommend a mechanical fan.
    Those engine bays are tight, I believe it would run a lot cooler with manifolds like ram horns or early 283/265 manifolds. Those tube headers especially long tubes dump a lot of heat in the engine bay. Manifolds are better to keep the heat in the pipes. Also headers will cook the starter.
    A short water pump and set up from a early 60s Chevy will give some more fan clearance.

    If it's running too hot with either radiator. It's got to be in the engine. Timing...engine bay too hot....problem with the engine......
    BTW, the performance of the aluminum radiators has been mixed.

    I know this has probably been checked, but other than a cracked flathead, my overheating issues have always been.....the water pump. They don't always weep.
    bchctybob likes this.

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