SB 400 Cooling Issues
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Instructor
Joined: Jun 2005
Posts: 156
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From: Liverpool NY
SB 400 Cooling Issues
I just intalled a 400 in my 82 and am having problems with the cooling. It has a 180 thermostat and the radiator only has one season on it. At idle it's running about 220 and I'm a little apprehensive about taking it out for a shake down. I've been told that I should get an aluminum (high volume?) thats rated for 450 HP and over. The computer dyno is putting me at about 480 HP.
Any thoughts on this guys?
Thanks a bunch.
Any thoughts on this guys?
Thanks a bunch.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
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From: Seattle WA
St. Jude Donor '14
Not enough information here to give a ton of advice, but a couple of questions.
Were the heads drilled with steam holes for the 400? Was a 400 head gasket used?
Have you ensured there is no air in the system?
Is the radiator the same, and if so was it working with your previous engine?
What type of fan system do you have?
I'd be a bit reluctant to start throwing expensive hardware at a cooling problem until you know where the problem's happening. If you're being told that a high-volume water pump will fix the problem, I'd push back on that pretty strongly based on my experience.
Were the heads drilled with steam holes for the 400? Was a 400 head gasket used?
Have you ensured there is no air in the system?
Is the radiator the same, and if so was it working with your previous engine?
What type of fan system do you have?
I'd be a bit reluctant to start throwing expensive hardware at a cooling problem until you know where the problem's happening. If you're being told that a high-volume water pump will fix the problem, I'd push back on that pretty strongly based on my experience.
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If your radiator is a copper/brass radiator it will not handle that motor adequately. When I put a 383 in my 61 the car had a copper/brass radiator and ran warm, over 225 at idle. I put a Dewitt's aluminum radiator in and it now runs 180 all day in any temps.
Drifting
Joined: Aug 2005
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From: League City TX
Where is your initial timing set? Are you running vacuum advance?
What do you have for a fan? Is the shroud in place?
How are you sure there is no air in the system? That issue gets a lot of people.
You may indeed need to upgrade the radiator, but I really doubt that you have reached the current systems limits at idle.
This is of course assuming that you know that the radiator was cooling correctly before the swap.
What do you have for a fan? Is the shroud in place?
How are you sure there is no air in the system? That issue gets a lot of people.
You may indeed need to upgrade the radiator, but I really doubt that you have reached the current systems limits at idle.
This is of course assuming that you know that the radiator was cooling correctly before the swap.
Instructor
Joined: Oct 2002
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From: jim thorpe pa
I'm at the same place, 406 running hot. I just ordered a dewitts rad today and it's getting the mark VIII fan. I like motorheads setup with the rad hoses, looks like they won't collapse (eliminates that ). Going with the 180 thermostat with 4 -1/16" holes drilled to eliminate air pocket (as recomended by forum members) more hp = more heat!
Race Director
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From: Foxfield CO 1970 Convertible
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Burning Brakes
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From: CA
i too have a 406 and only had a problem with overheating when sitting in traffic on a hot day with the ac on. I added a high performance fan and fan clutch from a later model corvette (different pitch to fan and larger fan clutch) and I also added a dewitts radiator. Problem solved from me.
Former Vendor
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http://www.dewitts.com
Race Director
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First, I would say that if only at idle it is reaching 220, then there probably isn't enough airflow thru the rad. I would try driving it for a simple test to see if that is the reason.
If it cools down a bit, it is airflow, if not test further, but at close to 500hp, you will likely need system improvements.
I don't think I know of anyone that can calculate the heat values created by their engine.
If it cools down a bit, it is airflow, if not test further, but at close to 500hp, you will likely need system improvements.
I don't think I know of anyone that can calculate the heat values created by their engine.
Former Vendor
Joined: Jan 2000
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From: Brighton
When it comes to C3's I actually offer (2) two upgrade options, not one size fits all. C3's have the largest capacity (btu rating) radiator than any other model from C1 to C6. The copper cores are huge, measuring as large as 27.5 long, and this stock cooling package could easily handle a 400hp motor when functioning correctly. 90% of C3ers don't really need aluminum radiators at all.
The first upgrade would be to simply replace the copper radiator with an aluminum one. To steal a line from the Be-cool ads, you'll drop about 20-40 degrees guaranteed. Our lab tests show about a 30% increase in btu removal to support this claim.
The second upgrade is to increase the air flow, and in this case it would be a dual fan package with 2800 cfm. Adding the fan results in about the same increase as the aluminum radiator did and now you have almost double the stock system and I've NEVER had one person tell me it wasn't enough. Never!
BTW, I search DeWitts
Le Mans Master
Joined: Jun 2004
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From: Seattle WA
St. Jude Donor '14
and that's why I (and DRIVESHAFT) noted above that there's some work to do before just tossing in a high-capacity cooling system. He's only making ~1.2 HP/CID..and that's not outside the realm of a properly functioning stock cooling system for a well-tuned engine.No question that the stock system can be marginal - and especially in the C3 due to the airflow challenges. It's not like the car isn't already known for cooling challenges....I just always suggest working the problem before just throwing $$$ at it.
Last edited by billla; Jun 7, 2009 at 12:01 PM.
Race Director
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
and that's why I (and DRIVESHAFT) noted above that there's some work to do before just tossing in a high-capacity cooling system. He's only making ~1.2 HP/CID..and that's not outside the realm of a properly functioning stock cooling system for a well-tuned engine.No question that the stock system can be marginal - and especially in the C3 due to the airflow challenges. It's not like the car isn't already known for cooling challenges....I just always suggest working the problem before just throwing $$$ at it.
The ORIGINAL and bestest
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From: Toronto Ontario
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No one has mentioned yet that a 400 sbc block is different from other sbc blocks because they have siamese cylinder bores with no water jackets between them. These blocks tend to run warmer than regular sbc blocks, and they need a better cooling system to keep things in check. Seeing as how I have a 500+ hp 406 in my vette, you might not want to listen to me about this though!!!
I am constantly amazed at how people build high hp engines and then wonder why they run too hot or overheat with stock or slightly better than stock cooling systems!!
Drifting
Joined: Aug 2005
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From: League City TX
Nobody yet has told this guy that he doesnt need to upgrade his cooling system.
He has been told that right now there are other things to check.
For what its worth, I also have some experience wih a 500+ dyno verified horsepower 406 small block chevy.
The car ran a copper radiator and a clutch fan and never overheated.
I am not saying that this will be the case with all such engines, but it is possible.
He has been told that right now there are other things to check.
For what its worth, I also have some experience wih a 500+ dyno verified horsepower 406 small block chevy.
The car ran a copper radiator and a clutch fan and never overheated.
I am not saying that this will be the case with all such engines, but it is possible.
Le Mans Master
Joined: Jun 2004
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From: Seattle WA
St. Jude Donor '14
Generalizing from a single aspect of experience and making recommendations without going through a troubleshooting process is...something else. Expensive, mostly.
I've built a number of engines approaching 500HP that had no cooling issues at all and without going to extremes of big, expensive radiators, etc.
Last edited by billla; Jun 7, 2009 at 02:02 PM.
Race Director
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Nobody yet has told this guy that he doesnt need to upgrade his cooling system.
He has been told that right now there are other things to check.
For what its worth, I also have some experience wih a 500+ dyno verified horsepower 406 small block chevy.
The car ran a copper radiator and a clutch fan and never overheated.
I am not saying that this will be the case with all such engines, but it is possible.
He has been told that right now there are other things to check.
For what its worth, I also have some experience wih a 500+ dyno verified horsepower 406 small block chevy.
The car ran a copper radiator and a clutch fan and never overheated.
I am not saying that this will be the case with all such engines, but it is possible.
Just want to see because I could always sell my cooling system and go back to stock
Race Director
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
That is not what I said. What I said is that some troubleshooting is in order before just swapping out parts. This is called being a mechanic.
Generalizing from a single aspect of experience and making recommendations without going through a troubleshooting process is...something else. Expensive, mostly.
I've built a number of engines approaching 500HP that had no cooling issues at all and without going to extremes of big, expensive radiators, etc.
Generalizing from a single aspect of experience and making recommendations without going through a troubleshooting process is...something else. Expensive, mostly.
I've built a number of engines approaching 500HP that had no cooling issues at all and without going to extremes of big, expensive radiators, etc.
Would love to see some pics of your 500HP motors in a C3 too with stock cooling system, I am changing back for sure if you come up with them
Last edited by MotorHead; Jun 7, 2009 at 04:21 PM.