BBC swap - now gets hot**MOD UPDATE

[pismorat]

I just swapped out the 383 stroker for a 454 bored & stroked to a 489 in my K10 w/ 1 ton drivetrain. The BBC on a 70* day just cruising the freeway up a mild hill will get up to 210 or and climbing. The timing is good, radiator is the same from the 383, thermostat is a 160*, good shroud and mech. fan. How can I keep it cool on hot SoCal days if I plan on hooking up the A/C...or worse for it yet, going offroading? Could the A/C condenser, tranny cooler, and engine oil cooler be not helping?

 

[4X4HIGH]

First off, you should be running a 180* t-stat. Secondly, the radiator for a SBC is smaller than for a BBC so a larger radiator is in order. As crazy as it might sound though, changing to a hotter t-stat will probably cure your issue.

 

[Cornfield creations]

This may be a given, but, does it have the coolant bypass hose from the intake to water pump? Some people forget it.

X2 on the thermostat and radiator. Consider doing a fan upgrade like the windstar swap

 

[Ned Kelly]

First off, you should be running a 180* t-stat. Secondly, the radiator for a SBC is smaller than for a BBC so a larger radiator is in order. As crazy as it might sound though, changing to a hotter t-stat will probably cure your issue.

Not that I doubt you, just being curious, what is the theory to how the 180* t-stat would help in cooling vs the 160*?

 

[4X4HIGH]

Not that I doubt you, just being curious, what is the theory to how the 180* t-stat would help in cooling vs the 160*?

Think of the t-stat as the "switch" that it is. The lower the temp the t-stat is the quicker it is going to open and close. The cooling is done by the radiator dissipating heat through the cooling fins of the radiator. If the coolant doesn't sit in the radiator long enough for heat to dissapate then it isn't very effiecent. Now install a hotter t-stat (the "switch" is gloing to open and close slower) and that same coolant is able to sit in the radiator for a longer period of time which gives more time for heat to dissipate.

 

[Cornfield creations]

The 160 thermostat will be open all the time. The idea with the higher temp thermostat is it will close and re-open to control temp. When it closes it will give the radiator a chance to cool the coolant in it, rather than constantly pushing hot coolant through in cycle.

 

[Cornfield creations]

Yeah what Scott said!

 

[USSkoval]

Think of the t-stat as the "switch" that it is. The lower the temp the t-stat is the quicker it is going to open and close. The cooling is done by the radiator dissipating heat through the cooling fins of the radiator. If the coolant doesn't sit in the radiator long enough for heat to dissapate then it isn't very effiecent. Now install a hotter t-stat (the "switch" is gloing to open and close slower) and that same coolant is able to sit in the radiator for a longer period of time which gives more time for heat to dissipate.

Might this only apply if the radiator is too small? If the radiator is large enough, it should still run cool even with no thermostat, right?

 

[pismorat]

Hmm, didn't know that about the radiator...so the 4-core that is in my truck isn't big enough? The radiator that was in the truck I pulled this motor out of looks to be the same size, so how can I tell? I can definitely jump to a 180* thermostat; would it help to go to a 195*? And the bypass hose does go from the waterpump to the manifold.

 

[4X4HIGH]

Might this only apply if the radiator is too small? If the radiator is large enough, it should still run cool even with no thermostat, right?

Running an engine without a t-stat will overheat since the coolant continually flows and doesn't stand in the radiator for heat dissipation to occur.

 

[4X4HIGH]

Hmm, didn't know that about the radiator...so the 4-core that is in my truck isn't big enough? The radiator that was in the truck I pulled this motor out of looks to be the same size, so how can I tell? I can definitely jump to a 180* thermostat; would it help to go to a 195*? And the bypass hose does go from the waterpump to the manifold.

A 4 core radiator is plenty for a BBC and AFAIK a 4 core was never used factory in a SBC truck. I think changing to a 180* t-stat will cure your issue as long as the fan and fan shroud are properly doing their job.

 

[GMC500]

I am from Saudi Arabia and the temp here are usually around 45-55 C (113-130 F) in summer
although I don't drive or wheel my truck a lot in summer but I don't have overheating problems

I have a mild 454 in a 1986 K15
I use an aluminum radiator from 1994-1998 BBC Suburbans
with thick HD fan clutch from 1980s BBC trucks ( yes fan gets noisy when the clutch engages )
and currently I don't have AC condenser in front of the radiator
my old condenser was very dirty and it didn't let much air to pass through so you need to make sure yours is in good shape

we usually don't use thermostats but I will try to use one and see the difference

hope this helps you

Ahmed

 

[rcamacho]

+1 more for a hotter tstat (180 or 195) with a good large BBC radiator. Another note, running a cool thermostat and allowing the engine to heat up significantly hotter and cycle back down is also a good way to blow gaskets or crack things. Thermal shock.

HD fan clutch that engages earlier and a big fan are also good additions.

 

[folkenheath]

Running an engine without a t-stat will overheat since the coolant continually flows and doesn't stand in the radiator for heat dissipation to occur.

That's just a myth, it's not true. The less time the water is in the radiator to cool, the less time it is in the engine to heat up. It's a very common myth but it's still a myth.

No thermostat will just take longer to warm up to the equilibrium temp, which will vary depend on ambeint air temp, airflow, water flow, radiator size, type, design, etc.

 

[pismorat]

I'll double check my radiator, but it was in my truck when I got it and it had the factory 400 SBC. The fan clutch is a heavy duty one. I will make sure everything is clean up front, but maybe I do need to start looking for Windstar fans...years to look for???

 

[folkenheath]

Another note, running a cool thermostat and allowing the engine to heat up significantly hotter and cycle back down is also a good way to blow gaskets or crack things. Thermal shock.

I think you have a typo there. A cool thermostat opens sooner, while the engine is cooler, not while it's hotter. Hot thermostats are for emissions, hotter heaters in the winter, and are required for some factory fuel injections systems because the computer won't run normal until the engine is up to factory operating temp.

 

[rcamacho]

Understood on cooler thermostats opening sooner. If the radiator/fan is undersized running a cooler tstat is really not much help. The engine is operating over an increased thermal range - it's the gradient that can cause problems.

The other concern is atomization with a cooler tstat - jetting or ECM changes may need to be made.

 

[rcamacho]

That's just a myth, it's not true. The less time the water is in the radiator to cool, the less time it is in the engine to heat up. It's a very common myth but it's still a myth.

No thermostat will just take longer to warm up to the equilibrium temp, which will vary depend on ambeint air temp, airflow, water flow, radiator size, type, design, etc.

Racing applications usually run a restrictor in lieu of a thermostat just to slow down the coolant so heat transfer from the block can occur...

 

[folkenheath]

I agree with you, if you run a cooler stat and your cooling system is not up to par, it won't help because the cooling system is then the bottleneck, not the t-stat.

Racing applications usually run a restrictor in lieu of a thermostat just to slow down the coolant so heat transfer from the block can occur...

That's not why they run a restrictor, they run a restrictor for consistent flow because they can't have the flow cut off at high RPM by a thermostat. And if they don't limit the flow it can run too cool. However, that's still not the best solution. Check this out, it's a good quick read...

A common misconception is that if coolant flows too quickly through the system, that it will not have time to cool properly. However the cooling system is a closed loop, so if you are keeping the coolant in the radiator longer to allow it to cool, you are also allowing it to stay in the engine longer, which increases coolant temperatures. Coolant in the engine will actually boil away from critical heat areas within the cooling system if not forced through the cooling system at a sufficiently high velocity. This situation is a common cause of so-called "hot spots", which can lead to failures.

Years ago, cars used low pressure radiator caps with upright-style radiators. At high RPM, the water pump pressure would overcome the radiator cap's rating and force coolant out, resulting in an overheated engine. Many enthusiasts mistakenly believed that these situations were caused because the coolant was flowing through the radiator so quickly, that it did not have time to cool. Using restrictors or slowing water pump speed prevented the coolant from being forced out, and allowed the engine to run cooler. However, cars built in the past thirty years have used cross flow radiators that position the radiator cap on the low pressure (suction) side of the system. This type of system does not subject the radiator cap to pressure from the water pump, so it benefits from maximizing coolant flow, not restricting it.

 

[rcamacho]

Thanks, good reading.