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overheating chevy 350

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wkbrdrob

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I just spent the afternoon at a buddies house getting his truck ready for an upcoming wheelin' trip. He's got a 77 Jimmy frame (stretched 18 inches) and drive train with an International crew cab pick body.:D We've had a terrible time with it overheating and here are a few things we've tried:

-Original International radiator
-Full size Chevy radiator
-Two radiators (smaller one in front of bigger one)
-Stock fan
-Electric fan
-Stock and electric fan
-New fluids
-New hoses
-2 electrical and 2 mechanical temp gauges
-3 different temp thermo's (160,180,190?) and no thermo
-High flow water pump

We've chased down all of the gremlins we can think of. We've heard rumors that a lean running carb can make a truck run hot, but wouldn't it just run piss-poor if it was that lean?:confused: Could the location of the engine/radiator in the engine bay have anything to do with it? I've heard another rumors Chevy's overheat if there is more that 50% antifreeze in the mixture.....

Any thoughts/ideas would be great. We've been working at this for a while, and we're going to go bald from scratching our heads for so long!:doah:
 
Water pump, carb too lean, distributor too advanced, cavitating hoses, blockage, stuck thermostat, etc, etc.

Never heard such a thing about the 50% antifreeze. It's BS. As long as you're getting airflow and the neck of the radiator is above the thermostat housing, placement shouldn't matter.
 
How do you know it is over heating? Is the temp reading too high? If so, how high is it? Is it just boiling over? If so, what pressure cap are you running? Did the over heating start after installation of the new water pump? Is the pump the right rotation? Is the pulley system stock and is the pump being driven at the correct speed? Is the lower radiator hose maintaining it's normal shape at idle? (Might collapse due to the suction of the high volume pump.) Is it over heating at an idle or under a load? Is there anything blocking the air flow over the radiator core? Where is the ignition timing set at idle and at full advance? Is the engine stock or have mods been completed on it as well?

A bunch of questions but they might help to figure out what is really happening.
 
MattK said:
have you looked into a blockage of some sort?
Click to expand...

forgot to mention we had it flow-tested.

And Smitty:

-We tried a total of 5 different temp gauges in the truck to verify we didn't have a bad gauge. We took a baking thermo and stuck it directly in the antifreeze and it read the same.
-I don't know what cap pressure he's running. I'll double check that.
-Overheating heating started right after the body was switched and the list is above is everything we've/he's tried. (Which got me thinking it could be the way the front grill is blocking and 1/8 of the radiator, but I'm not sure I would believe that.)
-Pump is normal rotation, high flow Edelbrock.
-All pulleys on the engine are stock.
-None of the radiator hoses are bulging/losing shaping/etc.
-It's overheatingg on load. If it's cold, we can start it up and it'll run forever without overheating. As soon as you rev it up or drive it around, the overheatin' starts.
-Nothing extreme is blocking the radiator. I part of the International grill is covering about the top 1/8 of the radiator.
-We checked timing yesterday with a light and if memory serves, at idle, with the vacuum advance unplugged, we we're at 5*. Plugged it back in and I don't think anything changed.
-The engine has been bored 30 over to roughly 383. Stage 1 RV type cam. Other than that, no special build-ups or mods beside the new $160 high flow water pump that didn't solve the problem!:mad:

Any more thoughts?
 
Chevy305 said:
Have you tried that Royal Purple Ice stuff? Supposedly drops temps by 10-20 degrees.
http://store.summitracing.com/partdetail.asp?autofilter=1&part=RPO%2DRP01600&N=115&autoview=sku
Click to expand...

haven't tried that one yet. We'll give that a whirl.

Just got of the phone with my bud and here are a few more things:

-Is there anyway to install a head gasket in such a way that it would block coolant flow to certain parts of the engine? Did Chevy can the coolant passage at all between years and the friendly neighborhood parts counter didn't see that there were two part numbers for the same applicaiton?

-They took the intake mainfold off last night and there are two coolant passages in the rear of the block that the intake does not have corresponding passage holes for. Has anyone had experience with an early 70's block and knows what I'm talking about? Could the incorrect intake manifold for the year (ie early block, later model manifold) be causing this type of overheating?

-The heads are not stock. Some Edlebrock heads, with 202 valves.
 
come to think of it, you probably have a blown head gasket. I don't think you installed it wrong, but it probably blew.

Oh and the intake coolant flow thing: thats how my truck is set up. Even the stock manifold had no rear coolant flow passage. I think its a chevy thing.
 
wkbrdrob said:
forgot to mention we had it flow-tested.

And Smitty:

-We tried a total of 5 different temp gauges in the truck to verify we didn't have a bad gauge. We took a baking thermo and stuck it directly in the antifreeze and it read the same.
-I don't know what cap pressure he's running. I'll double check that.
-Overheating heating started right after the body was switched and the list is above is everything we've/he's tried. (Which got me thinking it could be the way the front grill is blocking and 1/8 of the radiator, but I'm not sure I would believe that.)
-Pump is normal rotation, high flow Edelbrock.
-All pulleys on the engine are stock.
-None of the radiator hoses are bulging/losing shaping/etc.
-It's overheatingg on load. If it's cold, we can start it up and it'll run forever without overheating. As soon as you rev it up or drive it around, the overheatin' starts.
-Nothing extreme is blocking the radiator. I part of the International grill is covering about the top 1/8 of the radiator.
-We checked timing yesterday with a light and if memory serves, at idle, with the vacuum advance unplugged, we we're at 5*. Plugged it back in and I don't think anything changed.
-The engine has been bored 30 over to roughly 383. Stage 1 RV type cam. Other than that, no special build-ups or mods beside the new $160 high flow water pump that didn't solve the problem!:mad:

Any more thoughts?
Click to expand...

So, how hot does it get when under a load? If you replaced the water pump after the problem started, we can eliminate that as the source. The small amount of air flow restriction caused by the new grill shouldn't have that much of an impact. The timing sounds like it should be ok at idle (it might need to be advanced a bit to take advantage of the new cam...) but, you will need to find out how far it advances at higher RPM.

You mention some Edelbrock heads. Were these heads run on the engine before the swap into the new vehicle? Do you have the part number for the heads and do you know the part number for the head gaskets that were installed? I think Edelbrock specifies a FelPro #1003 gasket with their aluminum heads. Also, did you use washers with the head bolts? I think the washer for the #1 bolt needs to be clearanced to clear the valve spring cups.

Are you back to the mechanical fan? If so, does it have a shroud and a clutch for the fan?

GM blocks the rear coolant passages on their heads with the intake manifold. I've seen a few race engines that created a crossover passage but, I've never done it myself.

If the engine has been bored .030 over, the cylinder walls should still be thick enough to allow controlled heat transfer. I think .030 will give you somewhere around a 355, not a 383 (if it were that easy, everyone would be running 383's!!!)

These things can be a pain to find. You need to just start at the basics and go step by step until you find the problem. Good luck and keep us informed.
 
NO thermostat??

I think I read he had NO thermostat in it???...if so,that can lead to overheating under a load..the coolant gets hot,then rushes thru the radiator too fast to get cooled sufficiently..at least use a restriction washer if you hate thermostats (Moroso makes them)..I just use a 195 degree thermostat year round in all my GM products,and never had overheating problems..

And its true TOO MUCH antifreeze CAN encourage overheating...saw it firsthand in a friends fathers prized 66 Mustang 2+2..he used 100% prestone,and every time he took the car on the highway more than 5-10 miles,it buried the temp gauge!......
....he went koo-koo changing everything from hoses,radiator(put a brand new one in), to the water pump and thermostat--no change at all!!...--he was starting to wonder if a head gasket blew,but no smoke from either tailpipe--then one day,as he was checking his radiator coolant level,one of his sons asks "did you add water it too Dad"??--father says "NO,I dont want my radiator rusting out !"....I put PURE Prestone in it!!..WHY???

..then his son shows him a magazine article in one of his hot rod books, about the very subject of "too much antifreeze" VS water in the coolant mix!..he siphoned out some prestone,added a gallon of water,and it never heated up over halfway on the gauge afterwards,even on long high speed runs to car shows...:doah: ...anal owner error!!!:rolleyes: ...

I learned anti-freeze will FREEZE at slightly below zero, when I worked at a gas station one frigid winter--if we left the jugs outside on display ,they often froze and got all jello like!..adding water LOWERS the freezing point~!!!!--figure THAT out!--how does adding something that freezes soild at 32 degrees make something else NOT freeze even better???...:eek1:
 
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