Why is my sbc overheating

Maybe rad hoses need re-routing as you have them backwards ie. Fan clutch is defective even if new. You did not bleed all air from highest point in system. Paper or crap blocking water flow in radiator. A hose kink needs an inner hose spring to keep hose patent. Too much ethylene vs water ratio. Too many RPM at highways speed due to gearing issues.

Those are possibilities I would start with. Best, T. Mine does the same thing I'm sbc with stock radiator, and a sm Joined Nov 6, Messages 2, Location in my little world. Click to expand Last edited: Jun 6, Reverse rotation fan and fan clutch. I am guessing you are using the serpentine belt setup? Which is why you have a reverse rotation. A picture of your shroud might help.

Assuming all is well with the water pump, hoses, water jacket, timing, etc. There is a reason why propeller-driven planes have a maximum theoretical air speed, particulary in a dive. At some point there is only so much air that can be moved by the engine and propeller, after that the air in front is effectively compressed.

Thanks for the replies. I do have a serpentine setup which is why I have the reverse rotation water pump and fan. I have a trans cooler and power steering cooler in front of the radiator.

Give me a quick run down on the proper technique for bleeding the cooling system. I'll try to get some pics of the shroud. I was also wondering if my fan clutch wasn't working properly. I've thought about switching to a HD version to see if this fixes my issues. I'm TBI if that matters. I have a warn on the front of the cruiser, but it did the same thing before I put that on there.

I have read that cooling at speed is generally a function of radiator surface area. It sounds like you have that covered though.

Could your TBI be leaning out at cruising speed? Would it be worth it to bypass the coolers and remove them for a quick run down the road?

Does the radiator have any dirt in the fins? I actually pulled mine out and hosed it off in the driveway, there was quite a bit of dirt and mud stuck in the fins. I'm running a 19x26 Al radiator with a 7 blade clutch and never had a cooling issue with my SBC. Bret said:. I had similar issues recently and relocated the trans cooler to one side of the radiator versus the center, opening up a larger area of radiator surface. Maybe the water is not staying in the radiator long enough.

Small radiator fast flow not able to cool it before it heads back In to the block. At 50 mph, the fan is of little benefit.

I'd say the fan clutch was the problem if it was overheating at idle You should always use the correct thermostat for your engine. Without a thermostat the engine would have no way of regulating the minimum heat range. The bottom line is that the manufacturer designed our engines to run with them installed.

You can check the function of your thermostat a number of ways. One method is by letting the engine come up to operating temperature while feeling the upper radiator hose, once the thermostat starts to open, you should feel the hose start to take pressure and get hot. You can also use an infrared heat gun on the thermostat housing to observe the temperature change as the engine warms up.

Some may even remove the thermostat and check its function in a pot of hot water with a cooking thermometer. If a water pump is leaking it almost always means the pump has failed and needs replaced. Before you install a new pump, always check to make sure the impeller spins freely and has minimal end play.

You should always use the correct size pulleys according to what was on the engine from the factory. Undriving the cooling system spinning the water pump slower can lead to poor cooling performance.

If you're buying an aftermarket water pump be sure to pay attention to the direction of rotation. Some of the later style aluminum water pumps with a serpentine-belt drive system used a reverse rotation pump, which can lead to serious headaches if overlooked.

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Related Articles. Just trying to stir your juices here. Joined: Sep 3, Posts: 27, Profile Page. Motor have reverse flow water pump? Jalopy Joker , Apr 28, Joined: Nov 2, Posts: 2, Profile Page. What is the timing and is the vacuum advance connected to ported vacuum on the carb or manifold vacuum? Mechanical advance on the dist?

Total advance? Mr T body , Apr 28, Joined: Feb 14, Posts: 2, Profile Page. Did you change any pulleys or belt routing? Joined: Aug 16, Posts: 3, Profile Page. Air in the system could be a problem. After it cools, check the coolant level. Other thing, how do you know it is running hot? Are you using a reliable gauge? Do you have one of those "touchless thermometers"? Joined: Mar 24, Posts: 1, Profile Page.

I vote air in the system. Park it uphill, leave rad cap off and idle it for 20 or so minutes. Sting Ray , Apr 28, Joined: Sep 5, Posts: 2, Profile Page. Did you change the water pump? Once the air is out it won't happen again.

When you filled it after swapping it in your wagon, that's when the air gets in the system. Joined: Apr 12, Posts: 3, Profile Page. Joined: Apr 16, Posts: 3, Profile Page. I have seen factory chains start to go out at 75K and then temp of the motors start to creep slowly up the more the chain stretches out. Atwater Mike , Nailhead Jason , loudbang and 1 other person like this.

Joined: Feb 9, Posts: Profile Page. Take out the left and right aft freeze plugs and clean out the sludge. A coat hanger works good.

Joined: Sep 23, Posts: 49, Profile Page. Check the timing with the vacuum advance disconnected. Pictures of the engine, including the radiator and fan, would help us help you see if something doesn't look right. It may look fine to you, but have some obvious problem that we can't see, and you don't know about.

Those little hand held infrared temperature guns are very handy, you can buy them pretty cheap on the internets. If the radiator came with a 16 psi cap, it probably ought to have a 16 lb cap on it, instead of 7 psi.