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Correct radiator size?

JDizzle89

New member
I need to replace the radiator on my 04 GTP. I heard it's supposed to have a 1 inch core, but when I look around online, I see everyone saying it's a 5/8 inch core. I wanted to grab an AC Delco one, but I don't want to grab one that's too small. Which is correct?
 


you can use the 5/8 th's rad and it will be just fine. my 98 was a regal gs, came with the 1 inch, it blew up and i got the 5/8 th. temps didnt change one bit. and i had a load of bolt on mods.
 
RockAuto has the Spectra Premium at 1", and a few others at 7/8". You can also look at the 2004 Regal's, which list a few 1" ones (bought my replacement one there in 2009).

Since you're replacing, might as well get the nicest option. As mentioned, a radiator isn't a necessary upgrade, unless you're running many other items adding heat in the engine taxing the cooling system more. I only started upgrading when intercoolers, turbos, lower/drilled t-stat, and so on would cause more heat, work the system more, and reduce airflow over the radiator.

Not as simple, but you can also shop for some of the pre-97 GP's that came with 1" to 1-1/4" or so (ex. 1994 3.1L or 1991 3.4L GP list some), and adapt them to work (fan mounts and trans fittings changed by 2000). I got my GTP's 1-1/4" from a junkyard early-90's GP that must've had it recently replaced.
 
I put in a 1" and definitely noticed that the temps drop faster after romping on it. It's not gonna make it run cooler, just allow the heat to get out faster. Thermostat and fan settings will make it run cooler.
 
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