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Old 06-12-2013, 12:45 AM
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sbc 305 Overheating issue Help!!!

Hey, I'm a forum virgin until now because I am at a complete stand still. '89 k2500 with a stock radiator. '83 305 with mild porting done, mild cam, edelbrock performer intake, 1406 carb. HEI ignition 160 stat, ceramic hooker headers. (My 355 munched some bearings, bad lesson on fuel pressure, long story...) Any who, the 305 is overheating. Timing is at 10 degrees, brand new water pump, back flushed/flushed the entire system and double checked radiator. I'm running twin electric fans. One is on a hard wired switch, the other kicks on at 190. It will reach 220+ in a matter of 15 minutes just driving through town but hovers around 200 going down the road at 60mph. Stat and WP brand new.Any thoughts would be greatly appreciated!

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Old 06-12-2013, 04:06 AM
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Common problem with 305's.Especially in a 3/4 ton which most likely has lower gearing rear.Running A/C,or,pulling a load only compounds the problem.I had an 84 305 that ran 200ish all the time.Installed a large radiator.It helped,but,would still climb above 200 working hard such as hauling,pulling a load,etc.
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Old 06-12-2013, 08:18 AM
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Change out the 160 stat. It's open all the time and coolant is continually circulating. You need the coolant to spend more time in the rad to get it to cool. A higher rated stat will be closed or partially closed enough to restrict flow.
Try a 180 or 195.
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Old 06-12-2013, 09:29 AM
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Quote:
Originally Posted by Hermann21 View Post
Hey, I'm a forum virgin until now because I am at a complete stand still. '89 k2500 with a stock radiator. '83 305 with mild porting done, mild cam, edelbrock performer intake, 1406 carb. HEI ignition 160 stat, ceramic hooker headers. (My 355 munched some bearings, bad lesson on fuel pressure, long story...) Any who, the 305 is overheating. Timing is at 10 degrees, brand new water pump, back flushed/flushed the entire system and double checked radiator. I'm running twin electric fans. One is on a hard wired switch, the other kicks on at 190. It will reach 220+ in a matter of 15 minutes just driving through town but hovers around 200 going down the road at 60mph. Stat and WP brand new.Any thoughts would be greatly appreciated!
Probably should of put a 383 in it, as that's the power direction an old 3/4 ton's engine needs to move in not smaller. It appears the engine just has to work too hard at speed on the road. However, consider this inspite of the radiator appearing functional, a general assumption can be drawn that an engine that cools fine about town but slowly overheats the longer it is driven at highway speed there is a strong likelyhood that the flow through the radiator core is insufficeint. This is usually the result of fully or partially plugged core tubes, this stiff just cannot be removed by chemical cleaners and backflushing. In the days of copper brass radiators the thing was delivered to a radiator shop where the tanks were desoldered to allow their removal. The core was then rodded with a steel or hard brass rod that is pushed through each core tube to chip out the scale. The tanks are then resoldered to the core. The soldering requires a furnace large enough to accomodate the radiator with careful temperature control, this is not something that's very succesfull on the backyard barbeque. Additionally, the process of rodding often discovers the fact that the scale and crud is the only thing holding the coolant in so these jobs often became a new core or complete radiator.

Bogie
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Old 06-12-2013, 10:59 AM
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I did start with a 195 stat. Went to a 180 now to the 160. The only thing I haven't tried yet is a new radiator cap. It's only 2 years old as with the radiator but I'll give it a shot!
Blue print 396 short block shipped out today. 305 just has to last me another week or 2.
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Old 06-12-2013, 12:52 PM
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305 heads are commonly cracked.

Russ
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Old 06-12-2013, 01:18 PM
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Gonna need a new bigger radiator anyway to cool that 396,so,go ahead n GET R Done !!!
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Old 06-16-2013, 05:35 PM
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are you running the serpentine belt system your 89 came with stock on the 83 engine? If you are and it still has the 83 water pump with a serpentine system the water pump would spin backwards. The serpentine systems use a reverse rotation pump. Just a thought.
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