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Old 06-26-2006, 08:56 PM
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overheating small block chevy

i finally took the old 305 out of my truck!replaced it with 350 4 blot main old style(orange block),first engine was completely rebuiltand ran real hot.so i removed it and put in the same old style 350with maybe 30k on it,that ran good,but still runs hot.only things from original 305 are the water pump and radiator,and carb.i also added a edelbrock aluminum intake,but its still going way to hot?????are the water pumps different?i am getting another radiator tomorrow and will try that.i replaced thermostat 3 times and heater core isnt connected.whats wrong????

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Old 06-26-2006, 09:06 PM
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What year truck? Need more info.
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Old 06-26-2006, 09:14 PM
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1986 k10 4x4.also has a 3 row radiator wich is 17x28 3/8 (heavy duty)i assume?????
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Old 06-26-2006, 09:14 PM
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i too had a severe overheating problem with my 350 engine. you may be on to something tho, with the idea of changing your radiator. i called walker directly, and they told me that i had the wrong size radiator installed, and when i put a new one in, with the advise of the walker people, all was well. the engine temp. is now perfect, and i even run air condition without any heat problems. best of luck, i hope you have the same end to your problem that i did. richard egan
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Old 06-26-2006, 09:28 PM
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the 305 that was in it never went over 215 degrees,and it had broken rings in #3 cylinder.i cleaned that same plug probably 3 times a year!i was hoping a rblt 350 would keep me from under the hood,but why would 2 different engines do the same thing????i cut cat off and tried that too,only to weld back on i might try adjusting the carb too.maybe its to lean for the intake???????????just guessing at this point!
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Old 06-26-2006, 10:03 PM
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That 305 running at 215 is too hot. I'll assume that engine originally came with a thermostat around 180 degrees. If the engine has a shrouded mechanical fan then it shouldnt run too much hotter than that. Maybe 185-195. That said, you've had an overheating problem with all three engines. The stock three row radiator is the standard radiator. The 4 row radiators are the heavy duty units. The radiator should be able to cool even a healthy 350 without too many problems. My Blazer should have the same radiator you have (or at least very similar), I ran the stock 3 row radiator for quite a while with no problems until it just recently developed a leak serious enough to warrant replacing it. It kept a supercharged 350 relatively cool with almost no problems. I decided to upgrade to the 4 row because I have plans for a bigger, more powerful engine in the future.

So...

Do you have overheating problems all the time or just some of the time? Does it only overheat when idling or moving at slow speeds? Or does it run hot even at higher speeds?

Are you running a mechanical fan on that engine? If so, do you have a fan shroud?

It could also be possible that the radiator is plugged and not allowing enough coolant to circulate. It could also be why the other poster said his problem was solved by replacing the radiator. Not necessarily because the radiator was inadequate but because the original one was plugged.

Last edited by Blazin72; 06-26-2006 at 10:59 PM.
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Old 06-27-2006, 05:26 AM
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yes it does have a fan shroud and a stock clutch fan,also 3 different parts houses were trying to sell me a skimpy 2 row radiator,saying that was oe.i learned in the past to never go smaller,i always went larger if possible.i can let this thing sit behind my garage idling all daywithout a cap even on.its onlywhen i put a load on it the temp. goes up.its the same when driving it,it only heats up going up hills,going down them it cools back down. i can look in the radiator with it running and see the coolant flowing through the top 6 or so rows,not sure about the rest of the radiator though.some of the paint is peeling off the side tanks like it was too hot at some point,also some corrosion where the core meets the tanks.well anyways i am getting a new one today,i hope it helps!tried a flex fan also and same thing.
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Old 06-27-2006, 06:50 AM
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Is the computer still in use on this truck?
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Old 06-27-2006, 07:02 AM
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Try changing the fan clutch and water pump. Both cheap items.
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Old 06-27-2006, 07:18 AM
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How may miles are on the fan clutch?? If its leaking fluid from around the temp spring its time for a NEW one. These thing will wear out. I would go buy a new HD clutch intended for use with an A/C and maybe flush the radiator.

If Im not mistaken the 86 305 specs a 190 degree Tstat. My 86 does but I run a 180. Im about to do the exact swap in my c10 as the 305 has over 170k miles on it.
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Old 06-27-2006, 11:17 AM
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elec fan that

sucka
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Old 06-27-2006, 11:25 AM
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A 350 with a 3 row radiator (if it is in good shape) and shroud should not overheat if everything is in good shape. The fan clutch, thermostat, cap, overflow and all else should be checked. Also, check for compression leaking into the water system by seeing if the antifreeze is bubbling really bad. It also really can reduce engine temperature by hooking the vaccuum advance to direct manifold vacuum so you get more advance at idle. This will give you more pep off throttle as well. Avoid flex fans because they will destroy your fuel mileage.
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Old 06-27-2006, 06:22 PM
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Quote:
Originally Posted by wildjeffpa
yes it does have a fan shroud and a stock clutch fan...
There's your problem right there. Guarantee you the clutch has worn out by now and is not engaging properly. Replace it and be careful when your busting the bolts loose from it, you'll have fun with bleeding knuckles! Those damn fan blades will slice ya open nicely.. not.. that I would know For future notice on whether to replace the clutch or not, when the motor is cold, you should be able to spin the fan relatively well. When the motor is hot, it should not budge and be very hard to turn. Also, keep your eye on fluid leaking out from the clutch. You can try flushing your radiator out well too once you get a new clutch just for assurance. If you want to fork over a little bit more cash, I'd upgrade the water pump as well but that's up to you.
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Old 06-27-2006, 09:25 PM
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hey,thanx for the info on testing the clutch fan!i put a new radiator in it today(was pooring down too)but i didnt melt!anywayz it seems alot better gauges didnt go over 215 but i didnt drive it to far,because the exhaust is so loud!will give it a good test tomorrow on the way to work!what an ordeal getting a radiator for a simple chevy truck.well hopefully it wont overheat anymore ,i been doin all this work just to be able to go on vacation this week.finally got my boat goin(1984 checkmate with a 235 hp v6 )ready for action!and my truck is givin me all this greif!i hope i found the problem,my boat wants to go to deleware!and so do i!thanx for the posts!hope i can get r done!fish on!
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Old 06-28-2006, 07:00 AM
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Would you answer my question please? If the computer is not active and you left the same HEI in it, it has no mechanical or vacuum advance and the timing stays exactly where you set it, this would be why it overheats. Does it get only up to 215 when climbing hills or does it run there constant? if it runs there constant it`s not the clutch fan, as a thermal clutch fan disengauges at highway speeds for increased fuel economy and it`s not needed at speed since air flowing cools it anyway.
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