Re: KPack's 1954 Panama

Posted by DavidPackard On 2021/8/31 23:35:31

I think I’ve discovered a few fundamental differences in a Packard fuel system that may/should shed some light on the fuel cap leakage situation.

The Danchuk website claims a faithful reproduction of a tri-five gas cap, and that cap has a center through hole for a vent. We have at least three forum members that have reported leakage when this type of cap is used on a Packard. HH56 has posted a photo of an original Packard gas cap that does not have the center through hole vent design. So what is different between a Chevrolet (likely includes more GM brands) and Packard fuel systems for the same era?

PackardDon was on the right track, I think when he was talking about pipe bending dies, especially the long radius dies . . . fuel leakage may have a lot to do with the shape of the fill pipe. There is also the location where the fill pipe attaches to the tank, which is low on the Packard and high on the Chevrolet. This has a lot to do with the fuel level when the leakage stops. Now the fill pipe: The GM is a short pipe (remember it’s mounted at the top of the tank), with a short radius bend that looks about 45 degrees. The Packard (original not reproduction) fill pipe has a much longer smooth radius bend that allows the fuel slosh to be converted to a rising level in the filler pipe far easier than an abrupt bend. Based on Kevin’s experience the reproduction tank fill pipe is close enough to retain this characteristic of easily converting slosh to fuel level in the fill pipe.

The bottom line is to remain somewhat leak free the Packard fill pipe design and mounting location needed a vented fuel cap that does not feature a simple through hole, whereas the Chevrolet fill pipe and mounting could tolerate a through hole vent design in the cap. There is the possibility that the Chevrolet cap did leak but only when the tank was ‘really full’. There’s one other item, but at this point I only have photos, not hard measurements . . . to my eye the Packard ‘filler door’ appears to be measurably lower than the Chevrolet, perhaps as much as 6 inches. If that can be confirmed and the height from the top of the fuel tank to the spill line on the filler is less on the Packard, that would help explain a lot of the situation, in-fact that may be the single most important difference between the two systems. Does anyone know of a ’55 Chevy (non-wagon) that measurements can be taken?

For a while until we find a source for caps more like the original design we will be relegated to soda cans, tuna fish cans, or plumbing store stuff to keep the gas stains off of the fender.

dp