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Old 06-16-2012, 08:12 PM
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400 SBC engine cooling question

I have a 400 sbc that I have put into an 29 coupe. I am trying to reduce engine temperatures so I have tried a few combinations and seem to get the same results and would like to ask for any ideas anyone may have in reducing coolant temperatures. Currently I can cruse down the road at around 190 F but I have noticed as soon as I get into stop and go traffic the temperature goes up to around 210 F

Here are some thing I have tried they all seem to have the same results in temperature readings,

Test #1
with a clutch fan installed and no fan shroud and the engine running at idle for about 15 minutes it will peak at about 210F.


Test #2
A flex fan installed without a shroud setting at idle in about 15 minutes the engine also peaks at about 210F

Test #3
with a temp. cardboard fan shroud it sets at idle and within 15 minutes reaches the same 210F.


I currently have a transmission cooling installed between the radiator and fan blade with around 2-3 inches of space.

Do you think I should relocate the transmission cooler to help air flow through the radiator?

Should I reduce the space between fan blade and radiator?


With a new 160F thermostat when watching the temperature quage it appears the thermostat does not open until the guage reaches 190F. Do you think the intake water temperature is actually 30F higher than the thermostat?


any ideas or recommendations would be appreciated

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Old 06-16-2012, 08:18 PM
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What temp are you shooting for? 210 is nothing to be concerned with.
Did you check the t stat? In the past years I've had 4 bad ones out of 5.
I suggest you get a 180 T stat. Make sure you check it in a pot of water first.
Get it hot and make sure it opens. Then shut the heat off and check how long it takes to close.
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Old 06-16-2012, 08:58 PM
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Install alum heads add steam holes to the heads. Iron heads will trap a lot of the heat. Make sure there are 76CC heads. Also reduce the ignition timimg a little.

Last edited by lg1969; 06-16-2012 at 09:03 PM.
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Old 06-16-2012, 09:08 PM
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I would like to keep the cooling around 180 but there seems to be no change as I mentioned.

I replaced the thermostat yesterday thinking I did not put a 160�F one in. As i mentioned when watching the guage it appears it does not open unit 190. I am now starting to question my guage reading thinking two 160�F thermostats that open at the same temp when watching the quage probably are the same and the guage i am using is in error by 30�F. I guess I may try removing the quage and put it in some water and see how accurate it actually is.
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Old 06-16-2012, 10:17 PM
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beside whats been said, Did you pressure test the cooling system, did it hold?

Is there a bypass hole in the thermostat

Where did you find a 400?
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Old 06-17-2012, 12:51 AM
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Test the thermostat that you've removed, first. That'll eliminate a major variable.

PatM
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Old 06-17-2012, 09:38 AM
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400sbc

what kind of radiator do you have 400 small run a little hotter then a 350 because the clynder wall are closer. you may need a four core brass or two core alum.

Last edited by frankb; 06-17-2012 at 09:45 AM.
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Old 06-17-2012, 09:45 AM
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get another temp gauge and try it.
its possible your 30 degrees off.
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Old 06-17-2012, 09:54 AM
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try one of the new radiator caps from mister gasket it has the temperature built in it there work grate.
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Old 06-17-2012, 07:58 PM
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Your temps will read different depending on where the temp sender is located. If it's in the head, it will read different that being in the intake. Personally I prefer the head location.

How big is the tranny cooler compared to your radiator? You might consider going to a different style cooler and move it out from in front of the radiator to help air flow.
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Old 06-18-2012, 04:48 AM
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Be prepared to chase down multiple problems to get that last 20 degrees of temp drop. 210 is not bad at all, but I understand why you want to get it down and have a bigger margin for overheating.

On my truck I ended up making several minor changes, and I now run about 195 at idle when ambient temps are 95+ degrees.

- My 180 degree high flow thermostat was faulty. It opened at 180 initially but then got sluggish after it started to close the first time. It often failed to reopen at 180 when I tested it, and would not fully reopen until about 205. Replaced it with a new high flow 195 (with a bypass hole), which kept the temps much more stable and accurate.
- Fan clutch was old, and allowed temps to get to about 205 before it engaged. Replacement clutch engages at about 185-190 and it is very positive. I can easily hear the fan kick and raise the air flow. I have a stock shroud, and 18" fan with 7 (I think) metal blades
- Swapped to a Stewart Stage 1 high flow water pump. I have no direct measurement of its effectiveness, but temps appeared to get a lot better after I swapped to this pump.
- My aftermarket mechanical temp gauge was off by about 5 degrees. I still use it, but have to make the mental adjustment. My stock electrical gauge uses a sender in the head, and the mechanical gauge probe is in the intake manifold. I always compare both, but the mechanical gauge is much more useful. I also tried the mechanical probe in the head, and readings were very similar to having it in the manifold (most folks will tell you the head temp will be higher).

Bruce
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Old 06-20-2012, 11:43 PM
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heat

You can replace the thermostat with a water restrictor.Fan shroud helps. electric fans for extended periods of idle.Check your timing.move transmission cooler. bigger rad.better rad.seal grill gaps at side of rad so air has to go through rad and not around it.use rubber seals from an a/c car. Path finders have great rubber flaps for seals
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Old 06-21-2012, 10:40 PM
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400 cooling

My latest 400 build, I installed in a Corvette with no overheating issues. It actually ran cooler than the 350. First are you running 400 heads? If you don't have steam holes in the head it will overheat. Next use a Mr Gasket high flow thermostat. Do not use a clutch or electric fan set up. Use an old style fan with shroud.
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Old 06-21-2012, 10:43 PM
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Canada

Quote:
Originally Posted by spinn
beside whats been said, Did you pressure test the cooling system, did it hold?

Is there a bypass hole in the thermostat

Where did you find a 400?
They are quite common in Canada. I just sold one and I have one under my workbench. My friend has 3 of them.
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