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Old 04-04-2002, 06:13 PM
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Post chevy 400 to hot

I have a street rod with a chevy 400 bored 30 over and when i idle around town it heats up on me and going down the road its just fine. Ihave a flex fan on the water pump and a electric fan on the front of the raditor pushing air threw. Its a new radiator. Any suggestions appreciated. thanks

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Old 04-04-2002, 06:17 PM
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bigger fan

bigger radiator
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Old 04-04-2002, 06:42 PM
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Hi 36Ford, two quick things come to mind. A good fan shroud to help direct air through the radiator, and water pump rpm's (is the water pump spinning adequate rpm's at idle) in case maybe you changed any pully sizes and modified the speed of your water pump. These are just generalizations, some other guys might know of any specific problems related to the 400.
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Old 04-04-2002, 10:28 PM
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Agree with above...Do you have a down-flo or cross-flo (aluminum) radiator? It needs more air flow at low speed/idle. Maybe a more agressive water pump (impeller size) and a pull type electric radiator fan(s). Shroud is a must.

Maybe also a remote engine oil/transmission oil cooler to take some of the load off.
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Old 04-05-2002, 06:26 AM
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Is the system getting pressurized?, if the rad cap is not holding pressure it could cause the problem as you describe.
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Old 04-05-2002, 08:23 AM
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Are you sure the fans aren't fighting each other? I'd try pulling off the flex unit and trying just the electric. Could be your creating a dead-air space within the radiator area.
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Old 04-05-2002, 09:54 AM
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I would check to see if the electric fan is pushin or pullin, I would also add a good shroud or make sure the flex fan is about 1-2" from the radiator. I used a pump puley off a ac equiped 79 caprice. It is smaller than the truck one that was on the motor to begin with and will spin the pump faster. A pump intended for a car with AC is more efficient and will sometimes solve problems of coolant flow. Improper timing will also cause the motor to build heat

Good Luck
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Old 04-05-2002, 11:22 AM
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I will tell you what I learned on my rod, 30 Ford coupe with a 350, 330 HP. First lesson learned you need a shroud if you don't already have one. You can buy a street rod shroud for around $90. I wanted to spend my $90 somewhere else on the car so I scrouged around and came up with a shroud off of an old Ford Maverick, I found when I turned it sideways and trimmed it a little it fit good. The fan blades need to be in the shroud opening half way and the closer the fan is to the radiator the better it will work. I also learned that sometimes a high volume water pump will work against you, especially with a small radiator, reason being the water goes through the radiator too fast , it actually goes through before the radiator can cool it down. I also learned that if you think it will run cooler with out a thermostat, it won't , you need the thermostat, even after it opens it acts like a restricter and slows down the water flow so that the radiator has a chance to cool it. Be sure that your timing is right on as this will affect cooling also. And use a 50/50 mix of water and antifreeze. More water or more antifreeze than that will also increase temp. Also a radiator cap that is not holding pressure will increase temp, every pound of pressure decreases the boiling point by a number of degrees. Sorry this was so long, hope it helps.
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Old 04-10-2002, 03:35 AM
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Did you build the engine yourself? If you did, did you use the stock heads? When changing the heads on the 400 to non 400 heads you need to use the head gasket as a template to drill extra cooling holes that are unique to the 400. 400's have a reputation of overheating, but every old timer I have asked about them has said that it was because people weren't drilling the holes. If the heads are ok, I would check my fan shroud and some people say the flexfans aren't always what they are cracked up to be.
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Old 04-10-2002, 02:10 PM
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I agree with just about all of the above. Now my two cents[and almost worth that], oon my 1940 ford with 350 chev I started where you are , had same problems. put shroud on and took elect. off front of rad. it got a lot better. Took a/c cond. off front of rad. and put remote with shrouded under car BINGO had to install warmer thermostat for winter heat. On my 46 ford with 302 ford shrouded elect. fan [puller] works just as well. Both with Walker radiators. I am building another 40 and will use Walker Cobra with CCI shrouded elect. fan on 350 chev. All this stuff is important, you just have to start eliminating them, wish I'd had you guys 20 yrs. ago. Maybe this internet stuff might last after all.
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Old 04-10-2002, 02:43 PM
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first of all do you have fan shroud try one of them plastic fan blades my uncle got a 30 model A it did the same thing took care of the problem
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Old 04-17-2002, 02:10 PM
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Hi 36, Here's a good web site on over heating. It will probably have your answer.

<a href="http://www.inccn.net/techform.htm" target="_blank">www.inccn.net/techform.htm</a>


hope this helps
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