The Pennsylvania Railroad GG1: Why do some GG1's have large vents in the hood and some don't?

In February 1958, a snowstorm with high winds and very low temperatures created a very fine snow that penetrated the intake vent filters of the GG1. Once inside it melted and shorted out the traction motors. Every GG1 in the fleet was disabled causing chaos for days. As the GG1s failed the P5as were sent to tow them in and throughout the storm none of them failed. The P5as intake air vents were located much higher than the GG1s and it was concluded that this condition occurred only at the level of the GG1 intake air vents. In order to prevent a re-occurrence the original louvered vents were removed and new steel was welded in place to close the opening and new vents were installed in the hoods just below the pantographs. This modification was made to 40 of the GG1s.

There were two styles of vents used. One style was rather large with square corners and was used on 28 of the locomotives (see photo of surviving PRR number 4903) and the other was rather small with rounded corners and installed in 11 GG1s (see photo of surviving PRR number 4876). Two GG1s, numbers 4890 and 4900 actually had both styles of the vents installed (see photo of surviving PRR number 4890).

GG1 Road Number	Large Square Corner Vents	Small Round Corner Vents
4857	x
4876		x
4887	x
4889	x
4890*	x	x
4891	x	x
4892	x
4893 - 4996		x
4897	x
4898		x
4899	x
4900*	x	x
4901 - 4903	x
4904 - 4905		x
4906 - 4908	x
4910 - 4912	x
4914	x
4915		x
4916	x
4924 - 4926	x
4928 - 4929	x
4930		x
4931 - 4934	x
4936 - 4937	x

* 4890 and 4900 had both types of louvers.

Much thanks to Richard Duley who has helped to provide a great deal of the information found on this page.