Cooling Issue

[K.M.K. Racing]

I am having an issue cooling big block 454. Radiator is tilted back by about 20 to 30 degrees flexilite electric fans. I have a fill cap on the top of the manifold to eliminate air bubbles. Radiator is mounted in the front with a little bit bigger flow water pump. I have aluminum lines and pressure cap over 25 pnds. Radiator is a dual pass radiator fully aluminum.

Would a second radiator mounted in the back fix it, or create more plumbing problems?

What could be the problem? In the motor? jetting, timing, Just getting old? We are lost as to what to do need some help... Thanks in advance...

[Prerunin554]

Is this an all new cooling system? Or has it been around for a while? Do you have good access to clean air for the radiator? ie- do you have a skid plate in front of it or is it mounted in the rear right behind the rear glass? You might just need to get creative with some ducting. Also, the number one thing i have always seen with overheating issues is the radiator itself being clogged. Get the cooling system up to operating temp and turn off the engine, unplug the fans and put your hand on the radiator grills, just feel around for cold spots. Do you have the highest point of the radiator lower than your fill port on the manifold?

[OFFRD-JNKIE]

I know in the past big blocks have had problems with had gaskets you may check that also.......

[FABRICATOR]

The reasons for overheating are almost endless, but I would not be using a double pass for cooling a BBC.

[K.M.K. Racing]

The highest point is on the filler cap on the manifold. The radiator is brand new from jegs... I tested to see if the head gasket was blown, but its not.. The motor seems to run around 200degrees until we get up to higher RPM and really start pushing the truck then it jumps to 280 and won't cool back down. we have to stop and let it sit then go again gently.

We put in aluminum ducting to the radiator so it is getting enough air.. drilled holes in the skid plate to allow air flow. the skid plate really shouldn't be the problem..

I was also thinking, could it be a timing issue? or a jetting issue with the carb? Is there any reason to believe the motor has something to do with it and what has been the problems?

[Wild bill]

Check your timing. I had a roll pin failure on the Dist. gear on my BBF and the timing went kookoo and caused an overheating problem. A minimum radiator size for a BBC would be 27"x24"x4" double pass. Fluidyne makes mine.

[gawdodirt]

Never mentioned a T-stat temp. What stat are you running?

Never heard of a U-flow with a BBC, but that doesn't mean it won't work.

The radiator will require more air than most electric fans can move. Got the specs of the fan? A reasonable electric fan would need to draw near 35 amps to supply enough air while rolling. If it's not large enough, it could be limiting ram air flow while moving at higher R's.

Is it shrouded with bypass flaps in the shroud?

[John F2000]

I am having an issue cooling big block 454. Radiator is tilted back by about 20 to 30 degrees flexilite electric fans. I have a fill cap on the top of the manifold to eliminate air bubbles. Radiator is mounted in the front with a little bit bigger flow water pump. I have aluminum lines and pressure cap over 25 pnds. Radiator is a dual pass radiator fully aluminum.

Would a second radiator mounted in the back fix it, or create more plumbing problems?

What could be the problem? In the motor? jetting, timing, Just getting old? We are lost as to what to do need some help... Thanks in advance...


Assuming your engine is ok. And assuming you have a large enough radiator. Your fans may not be big enough. If you are using electric fans on a big block, You need the biggest and the best. We had cooling issues on a big block. Were running 2 14 inch fans. Problem was solved when we used 2 16 inch spal fans that actually were wider than the radiator. Problem was solved. Prior to this we chased all other issues, ducting, thermostat, head gasket, etc... Nothing worked, It all came down to the fans.

[bajaruner11]

Fans are a big one and most likely your problem, a mechanically driven flex fan and shroud maybe your only hope, but here are some ideas to check out.


-What water pump are you running? A high flow pump will help, a little spendy but you have a beast to cool, check this out, there good pumps for the $$
http://www.stewartcomponents.net/Merchant2/merchant.mvc?Screen=CTGY&Category_Code=ChevyS4

-Are you running an under drive pulley set up that may be slowing the pump to much?

-Did you try to run the truck without the skid plate? Don't care about "holes" just try it with the plate off to see what happens.

-Has the system been fully burped out of any air?

-Ignition timing on a big block should be about 36-38* total advance depending on the engine combo.

-Is the beast being feed correctly? Fuel pressure at wide open throttle should not drop below 3 psi. 3+ is ok.

If your concerned about jetting, pull a couple plugs after a hard run (No idling) just shut it down and read the plug color. See this link if you need to learn more on how to do this:
http://www.empirenet.com/pkelley2/sparkplugreading.html

-I don't know what your intake manifold set up is, however with some aftermarket intakes like Edelbrock and others it may have a front and rear coolant boss in the manifold itself.
In some cases I have had to drill and tap the manifold myself.
You can run water lines (-10) from the front to the rear of the manifold, this helps to pull poorly circulating hot water from the back of the heads and put it back into circulation. As it is with most V-8 configurations (particularly Chevy) the water does not circulate well in the rear of the block and heads so it tends to heat the entire system. Currently water enters the front of the block and exits the front of the intake manifold leaving the water in the rear sort of stagnant. This mod helps tremendously in getting water circulation going to the back of the system, and putting more water into rotation.

[K.M.K. Racing]

Thanks for your help, I will try this out and let you know.

[partybarge_pilot]

Never mentioned a T-stat temp. What stat are you running?


Well? Also, what did you do with the radiator bypass hose?

[bajaruner11]

Well? Also, what did you do with the radiator bypass hose?

That too! ditch that thing.

[mebuildit]

I am having an issue cooling big block 454. Radiator is tilted back by about 20 to 30 degrees flexilite electric fans. I have a fill cap on the top of the manifold to eliminate air bubbles. Radiator is mounted in the front with a little bit bigger flow water pump. I have aluminum lines and pressure cap over 25 pnds. Radiator is a dual pass radiator fully aluminum.

Would a second radiator mounted in the back fix it, or create more plumbing problems?

What could be the problem? In the motor? jetting, timing, Just getting old? We are lost as to what to do need some help... Thanks in advance...


The reason to me is that your radiator is tilted back. The air does not have a chance to enter the fins on your radiator properly. If you can stand your radiator up to 90 deg. or as close as you can this should fix your problem. I have seen this problem before.
See if you look straight on to your radiator now the air will just roll up and over. Air is lazy and usually doesn't do what you think it will do. If it were me I'd put that thing upright and if you can't make a air deflector of some sort to help guide the air into your radiator.

Good luck with your project.

[Co-Dog]

Are you running a thermostat? I've seen them removed under the assumption that more flow is better cooling.