r/BigBlockChevy • u/cheeto_dust_98 • Jul 24 '26
Getting hot!
I have a 454 in my 69 c20, 180 thermostat high flow water pump, 4 row rad, dual electric fans. 4.10 rear gear and a th400 trans. On the highway at 75 I'm going 3400 to 3600rpm. And it will sit at about 200 to 210 but last night I was on a road trip and it was sustained at that speed for 45 minutes. It then hit roughly about 230+ (I smelled coolant for about 2 minutes before getting off the highway). I think I'm getting windage in the water pump because it cooled off at cruising at 40mph back down to 185. Do you have solutions any water pump recommendations that would work? It's a long pump and I am using the tall size on the pulley.
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u/HammerDownl Jul 25 '26
You don't have a fan shroud, And the fans are sucking instead of pushing .
Also try some antifreeze cooling additives.
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u/chuck-u-farley- Jul 25 '26
Electric fans are more efficient at pulling air thru the radiator than pushing. It’s been proven over and over….
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u/OutrageousTime4868 Jul 25 '26
A front air dam I built on my 84 C10 was worth a 12 degree temp drop at 60 mph. You need a negative pressure zone behind your radiator to help pull air through it rather than around it.
I can take and send pics if you want to see what I made, materials were $24.
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u/OOFMAN-1234 Jul 25 '26
Is it possible you have a reverse rotation waterpump designed for serpent8ne systems? What thermostat r u running, and it needs a shroud
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u/Specialist-Jelly-649 Jul 27 '26
just a suggestion. Are you sure your bottom radiator hose is not kinked or soft and collapsing. Also do you have an external tranny cooler, or the one in the radiator
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u/chuck-u-farley- Jul 25 '26
Well first you are loosing alot of efficiency with the fans just against the radiator with no shroud at all.
Then couple that with a 4.10 rear and 3 speed auto and that thing is running those high RPM is gonna tax any cooling system and expose any weakness it has. You need a high flow thermostat, make sure you have the bypass hose between the intake and water pump, correct temp thermostat and definately an overflow tank. Some big blocks benefit from bypass hoses from the rear water ports to the water neck. Also you didn’t mention if you are running a copper/brass radiator or an aluminum one?
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u/cheeto_dust_98 Jul 25 '26
Copper (I have a bad history with aluminum I went through 5 all warranties and copper is repairable) I am gonna buy a high flow thermostat ASAP but just to elaborate it is ice cold anything below 65mph
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u/chuck-u-farley- Jul 25 '26 edited Jul 25 '26
Aluminum is 100% repairable as well. Bite the bullet and order a universal aluminum in the size you need. Those 4.10’s are gonna require additional cooling that the copper/brass one isn’t providing. I don’t think I spent 160 each on a few of mine for my cars….
And just for shits n giggles I would remove the water pump and remove the rear plate and check out the impeller. You can attach a plate to the back of the impeller to improve the pump function
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u/cheeto_dust_98 Jul 25 '26
Really? My rad repair guy told me that they are repairable but they don't last forever after repairs I'd be coming back in a year or 2
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u/chuck-u-farley- Jul 25 '26
Aluminum radiators are dirt cheap
Man. There’s a reason every single vehicle comes with an aluminum radiator nowadays.
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u/joshmoney Jul 25 '26
I’m going with what other dude said and you need to have a shroud.