Inspection/Access port for Longitudinals Options

[Richard Casto]

Ok, while rebuilding the rotted out passenger longitudinal on my car I came up with an idea. How about a port that can be used for access to the interior of the longitudinal for inspection and other purposes. For example while my passenger side is going to be fine after I reconstruct it, I "think" the driver side is golden, however, I don't know for sure. Even if it is good, I would like to treat the interior of the driver side with some type of rust proofing (Metal Ready and then POR 15 most likely). But how do I get into that section without cutting a hole and then welding it back?

Here is my idea. In the front fender well there is a small area that if it had a port cut in, would allow you to view and/or access the entire length of the longitudinal. Items like the heater tubes and brackets will be somewhat in your way, but otherwise it is a straight shot down the length from here. I was thinking that a hole (maybe 1" in diameter or so) could be cut in the wall. Some type of "bung" (large diameter flat nut) could be welded in place and then a plug could be screwed into the bung. You could seal the threads with your sealent of choice, etc. to keep anything from getting in. An example of using this would be that a wand used to spray Metal Ready or thinned POR 15 should be easily snaked down the length via this. Every few years you could open it up and check to make sure things are OK. I don't like cutting up the car to do custom stuff, but I think this is maybe something I can live with.

In the photo below is where I am thinking about doing this.



I have looked at McMaster-Carr and I can't find a flat nut or some other type of weldable nut or bung that is of large enough diameter (1" or so). I think the plug is going to be easier to source than the bung. I would prefer metric threads, but I am thinking if I have any hope it might end up NPT or some other non-metric thread. Any ideas for source of a large diameter bung or how to create my own (i.e. thread 1/4" metal plate to make my own)? Is this a good idea or not? Opinions welcome!