BB runs hot

gottype · Jun 20, 2009

I have a 69 with a stock 454 and alum. radiator and duel 11in fans,160 t-stat, with 3:08 gear.It overheats at idile and at 60mph. I have the heater hose fittings plug off at the engine, will this cause a problem like this ?
I have the bypass still hooked up at the waterpump,the radiator is new and made for a BB..

Thanks Jay

fatblock · Jun 21, 2009

gottype said:
I have a 69 with a stock 454 and alum. radiator and duel 11in fans,160 t-stat, with 3:08 gear.It overheats at idile and at 60mph. I have the heater hose fittings plug off at the engine, will this cause a problem like this ?
I have the bypass still hooked up at the waterpump,the radiator is new and made for a BB..

Thanks Jay

Whats your version of hot?

Eric Kammerer · Jun 21, 2009

What's your timing, and which carb are you running? Do you know what jets/rods are in the carb?

Retarded timing and carb too lean in certain idle/part throttle circuits would be something to look at, based on what you described. I have a similar setup, except I have an OE style thermo clutch fan. I recently had an idle overheat issue, and the primary problem was the distributor had slipped and lost 8 degrees of timing at idle. Big blocks are so forgiving on timing (will run well across a wide range of timing), it isn't as easy to notice that it is running lousy.

If you search "overheat timing" here, there are many threads with ranges of timing people are running with their BBCs. BBCs run hotter to begin with, which is probably why George asked how hot you think is hot. 205, 215 on a BBC with iron heads is not unreasonable. It will not run 160 though...

gottype · Jun 21, 2009

The temp gauge reads 220 and when I cut it off it blows water out the overflow. I stop driving it at 220 but think it would get hotter if I kept it running.
Checked the timing this morning, ok. I have a 750 holley. Pulled the t-stat out and drove it, it took longer to get hot but still got there. Put 3 5/32 holes in t-stat and drove it again, still got hot.

Do you think the water pump could be the problem, its the original I think from the 70s.

Thanks again Jay

Skeeter55 · Jun 21, 2009

gottype said:
The temp gauge reads 220 and when I cut it off it blows water out the overflow. I stop driving it at 220 but think it would get hotter if I kept it running.
Checked the timing this morning, ok. I have a 750 holley. Pulled the t-stat out and drove it, it took longer to get hot but still got there. Put 3 5/32 holes in t-stat and drove it again, still got hot.

Do you think the water pump could be the problem, its the original I think from the 70s.

Thanks again Jay

It sounds like the 160* stat is one of the problems, what i mean is the stat is open at 160* and then the BB likes to run 180-190* so whats happening is the stat is staying open and not allowing the cooling system enough time to cool down. So put a 180* stat in with 2-1/8 holes in it, then start the motor with the cap off, up hill to allow any air pockets to escape. Then warm up the motor with the cap off and watch inside the radiator for coolant flowing once it reaches 180* temp.

Try a 180* stat with the 2-holes and see what happens, don't forget to check for coolant flow inside the radiator, this will help eliminate the water pump.

Z15CAM · Jun 21, 2009

I agree with Skip the 160 thermostat is too low. You should be running between a 180 to a 195. Generally the thermostat will trip at around 210 or 215 if the Sensor is located in the Intake Cross-Over and probably around 215 to about 222 if located in the cylinder head. Are you running the Stock Cast Cylinder heads? Do as Skip advises and repeatedly squeeze the Rad hoses to prevent air locks. One thing you can do is run the Windshield Defroster at Full Hi-Temp. If the Defroster Air remains cool or does not get hot were you can barely hold your hand in the air flow after the Thermostat Trips you most likely have an Air Lock. You can tell when the thermostat trips by holding your hand on the Upper Rad Hose as it will suddenly get too hot to hold and at this time the Defroster air should also become very hot.

Set the electric fans to cut in a couple of degrees above the noted temperature that the thermostat trips and definitively not below this temperature. After the thermostat trips, it should take another a 10 minutes or more for that Big Block to heat up enough to kick in the Electric Fan.

BBC's are very cold blooded and have to be running for about 20 minutes before reaching maximum operating temperature - then it's a furnace. Keep this in mind before you punch the throttle to the floor - you want them hot ;o)

Considering the price of gas I usually get under way to let the engine warm up. I run 15w 40 weight Oil and once the Oil Pressure drops to a constant 60 lbs at cruise the temp should just about be right on the "Thermostat Rating". Then it's time to do what you going to do ;o)

Another thing about BBC's. If you park your car in a lot that evening and it snows over night; the next morning, your ride will be the only car in the lot with no snow on the hood - LOL

gottype · Jun 22, 2009

I finally got it to run210-220 by pulling the guts out of the t-stat. Drove it for over a hour and thats as hot as it got.Its close to 100 degree's here during the day. Drove it last night (81 degree's) and it ran 200. This will work for now but plane on adding AC, so I will try the other stuff that was suggested.

Thanks Jay

PS: we have a few snow flakes about 4 years ago!

fatblock · Jun 23, 2009

Do you think the water pump could be the problem, its the original I think from the 70s.

Thanks again Jay[/QUOTE]

Yes ..the water pump could be the problem, more so by design and pulley ratio vs mechanical fail.The fact that hogging out the t-stat guts resulted in lower temps is a good indicator that you have low flow thru the core at idle and at 60 mph with 3.08/1 gears.
Assuming the coolant system is purged of air and no issues with steam pockets occuring ..a higher velocity thru the rad core has a turbulent affect and exposes more of the coolant to the inside of the tube surface that now transfers to the cooling fins.
If your coolant capicity and rate of exchange exceeds your engines ability to creat heat..you would require a 160* stat just to maintain operating temp.
Move as much coolant as you can thru the rad and use a t-stat to regulate your desired operating temp.

Skeeter55 · Jun 23, 2009

fatblock said:
Do you think the water pump could be the problem, its the original I think from the 70s.

Thanks again Jay

Yes ..the water pump could be the problem, more so by design and pulley ratio vs mechanical fail.The fact that hogging out the t-stat guts resulted in lower temps is a good indicator that you have low flow thru the core at idle and at 60 mph with 3.08/1 gears.
Assuming the coolant system is purged of air and no issues with steam pockets occuring ..a higher velocity thru the rad core has a turbulent affect and exposes more of the coolant to the inside of the tube surface that now transfers to the cooling fins.
If your coolant capicity and rate of exchange exceeds your engines ability to creat heat..you would require a 160* stat just to maintain operating temp.
Move as much coolant as you can thru the rad and use a t-stat to regulate your desired operating temp.[/QUOTE] X2

BB runs hot

gottype

fatblock

Eric Kammerer

gottype

Skeeter55

Z15CAM

gottype

fatblock

Skeeter55

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