That's not a one size fits all question. What year? I'm not sure when Chevy started using a pressurized system but my '38 is 0 pressure and it was that way for years. Someone will come along with the specific year that Chevy went to a pressurized system. Basically you can look at your overflow. If it works through the cap it's likely a pressurized system. If it's like mine and is separate it's not. My overflow is down the radius of the upper tank, away from the neck and cap.
Last edited by Tiny; 04/28/2016 12:52 PM.
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