Author Topic: Rebuilt Motor Overheating  (Read 999 times)

Offline bigben5054

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Rebuilt Motor Overheating
« on: April 26, 2020, 03:00:44 PM »
I recently rebuilt the 350 in my 1979 K20.  Flat top pistons .40 over, vortec heads, mild cam, Holley 670.  Nothing too exotic.  First time I started it and revved it up to 2000 to break in cam and it only went about 5 minutes before the water temp was pegged on the stock gauge.  Radiator was leaking too.  I shut it down.  I replaced the radiator (3 core) and also put in a new aftermarket mechanical water temp gauge just in case.  This time it only ran about 4 minutes before it hit 250 degrees and counting, so I shut it off again.  Wondering what might be causing this?  To fill with coolant, I just filled the radiator before starting, then topped it off after it had run a minute or so and put the cap on.  Wondering if I missed something there and maybe have trapped air?

Offline MIKE S

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Re: Rebuilt Motor Overheating
« Reply #1 on: April 26, 2020, 03:43:42 PM »
Couple of things come to mind. Remove the thermostat and try running it without one temporarily. If it still overheats fast it could be a circulation problem. Are you using a vortex pump? Serpentine belt pumps are reverse rotation. One more thing to check is the intake gasket. You say you are using vortex heads. Do you have the correct intake gasket for the intake you are using. Some intake gaskets are blocked on the rear water ports and can be put on backwards blocking the front ports for the crossover to the thermostat.

Offline bigben5054

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Re: Rebuilt Motor Overheating
« Reply #2 on: April 26, 2020, 07:00:25 PM »
Thanks Mike.  Problem is solved.  It just needed to run some more and let out a big ol burp.

Online VileZambonie

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Re: Rebuilt Motor Overheating
« Reply #3 on: April 27, 2020, 10:45:55 AM »
Best way to fill a new engine is to hook everything up except for the waterneck and fill the coolant all the way up to where the thermostat sits. Then install the T-stat and housing to finish filling. the next best thing anyone here should own is a spill free funnel. https://www.tooldiscounter.com/product/lisle-spill-free-funnel-lis24680?gclid=Cj0KCQjwhZr1BRCLARIsALjRVQOSzYpIvgxGSXl2X5tp5ZFqupsa_8DwD8DQmADyqYiVKa5AacGDcq0aAuvpEALw_wcB
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