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Old 03-17-2006, 01:36 PM
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455 pontiac runs hot! What to do?

Howdy guys!

Well, just got my rebuilt 455 installed in the firebird. I've got an aluminum radiator.

While driving above 40mph, the engine runs real cool--160, but when you stop and idle in gear, the temp climbs. If you rev the engine up a little, it also tends to cool down, although at a slower pace. This leads me to believe the radiator is fine, but the fan is suspect. Right now I'm running a flex fan on an extension which puts it inside the factory shroud.

What should I do? Go to a clutch fan, or electric? Any ideas?


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Old 03-17-2006, 02:41 PM
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sounds like you have a problem with not enough air flow.personally i like to use the best electric fans i can afford.you can get very good ones at the junk yard off of newwer cars or i found an excellant deal on some pro comp electronics electric fans,roller rockers and varrious other things.the price seems to good to be true but i have bought 4 of the e. fans so far and they seem to fine,unless they quit working after a month.they have a 1 or 2 yr. warrantee on them though if you keep your reciepts.their at whiteperformance1 on ebay motors.
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Old 03-17-2006, 03:55 PM
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Assuming that you did re-install the water pump tubes, check out this site:


There is information on making sure the water pump is properly set-up to provide good circulation.

Also, you may consider an aftermarket high-volume water pump, as 455 is a lot to cool with an OEM pump that was designed to cool from 301 to 455 cubic inches.

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Old 03-21-2006, 08:21 PM
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do you know if the block had been filled by someone else before you?

clutch fans use less HP that flex fans i'been told. you might need a bigger rad. maybe colder plugs? see what machine shop had to say? get anything out of it?
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Old 03-22-2006, 09:38 AM
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Make sure the fan is halfway (looking from the side of the shroud) in and out of the shroud. Flexfans are about the least efficient fan you can be running. There was a fan comparison in one of the mags a few years ago and the stock four blade fan from a 283 outperformed an aftermarket flexfan in both cooling and horsepower draw.
Before you start spending money on new radiators and custom pumps make sure the shroud and fan are optimized. Get a factory clutch style fan and be sure the positioning is correct as I stated above.
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