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347 stroker getting HOT

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  • 347 stroker getting HOT

    Thanks for reading this somewhat long post! I know there have been a ton of posts on overheating rebuilds, but I've yet to find the issue on my 347 stroker (carburated early 302 block). I have a serpentine system, with reverse rotation pump and matching timing chain cover, performer RPM heads and intake, edelbrock Thunder carb, high flow mechanical water pump, and 3 row direct fit aluminum radiator. I've confirmed that it is reverse rotation, running counter clockwise as you look at it. It's heating up to about about 15 minutes. It slowly creeps above that temp after 20 minutes, then I feel I have to shut it down.

    Here's an approximate timeline after startup (running in idle):
    - After startup, it reaches 160 at about 5 minutes. Thermostat opens. I changed the 180 to a 160 to see if it made any difference. It didn't, other than slightly slowing the heating up.
    - 7-10 minutes -- looks like it's going to stabilize as the electric fans kick on at about 200-210, then keeps on creeping up.
    - 12-15 minutes - hits 220
    - 15-20 minutes - hits 230, then, again, looks like it's going to stabilize. It then slowly starts to creep up, and I shut it down. I've never let it go past about 235.

    Step 1: I've tried two new thermostats, with no changes
    Step 2: Took a temperature gun to the thermostat housing and upper and lower radiator hoses to confirm the temp gauge was correct and water was actually flowing through the radiator. It all looked kosher
    Step 3: Added two more electric fans to see if it's an airflow issue. I initially put on 2 10" fans with a custom shroud, but the fans only covered about 60% of the radiator. I put on two more 8" fans to cover about 90% of the radiator (yes -- four total fans!!). That slowed the heating a little bit, but not much. If you're thinking that's crazy, it's because I can't go with one large fan due to clearance issues with the new setup.

    Next step: I ordered a new fan temp switch -- I'm thinking since the fans aren't kicking on at 185 (which is the temp switch I have), maybe it's getting too hot where the fans can't "catch up" once the fans kick on. I suppose in the meantime I could cross over the temp switch to manually turn on the fans at 185 to at least test my theory.

    Finally: if that doesn't work, I think I'll have to tear the engine back down to see if the head gaskets are on wrong. It is my first rebuild, but I used an 289/302 engine assembly manual which shows pictures of the proper way to install the head gaskets (not to mention, the head gaskets were labeled!), so I have a hard time believing I made this mistake...although it seems to be fairly common based on other posts I've read. Plus, if this were the case, wouldn't it heat up a LOT faster???
    Any suggestion on further troublshooting before I take my beautifully sounding engine back to pieces?
    '66 Coupe Frame Up In Final Stages
    347 Stroker, Tremec 3550, 9 inch rear, 4X power disk brakes

  • #2
    stuck thermostat may not be closing to allow time in the radiator to cool it before entering the engine again. does it cool down if your driving over 35 if so maybe its airflow issues with your fans.
    '66 Mustang Cp. (Met, Blue) 342-425Hp, 8" 3.55, C-4
    '86 Ford F-150 4x4 5.0 4 Speed


    • #3
      Thanks...that crossed my mind, but I've already tried 3 different thermostats since that's an easy/cheap fix for a common issue. I also thought maybe the high flow water pump and high flow thermostat could cause that issue (ie not enough time in the radiator), but I ran the old engine without a thermostat and never had problems. Do you think going back to a standard thermostat could make a difference?

      I also thought maybe the system had air in it, so I drilled a hole in the thermostat to help burp out possible air when filling it.

      I'll try getting it up to highway speeds to see what that looks like...just a little hesitant because my last road test (about 2 miles through the local neighborhood at about 30mph), I had to stop and shut it down for about 10 minutes to cool things down.
      '66 Coupe Frame Up In Final Stages
      347 Stroker, Tremec 3550, 9 inch rear, 4X power disk brakes


      • #4
        The head gasket it is a easy one, the head gasket has a tab that sticks out in the lower front corner. I attached a pic I found on the internet where you can see this tab sticking out between the head and the block, if the head gaskets are backwards this tab will stick out on the back side. It is only on the front end of the gasket so you will only see this tab on the front or the back, but not both, so if the tab is sticking out the front your head gaskets are on the right way, if they are out the back, well then you got them backwards. Do you have a spring in your lower radiator hose? The water pump could very well be sucking the lower hose shut. Also make sure the hose isn't kinked tightly to make the bend from the radiator to the water pump as this will restrict flow also. head gasket.jpg
        1970 mustang coupe restored with the help of my dad and lots of friends, 306, 480hp/392ft torque n/a pump gas, magnum T-56, 5.14's


        • #5
          Are you just getting this set up running for the first time?

          It may not be a water flow or air flow issue at all. What is your initial timing set at? Do you have a vacuum advance on your distributor and is connected ported source on the carb? Timing can also be a cause of overheating.

          Just a few questions to start.
          11 F-250 KR PSD - Wife's Daily Driver
          05 F-350 DRW KR PSD - My Daily Driver
          70 Torino GT 351C-4v with a "shaker"
          69 mach1 351W-4V engineless at the time!
          Mustangs and More Member #23
          Gearheads Member #177