When my son and I added tube fenders to my 79CJ7 I didn't like the way they looked with the factory inner fender wells...so we decided to see how they would work without them. In my opinion, after trimming the fenders the way the vendors indicate to do, the inner fenders don't offer much in the way of structural support. If the firewall area and the radiator shroud are in good shape, and if you use quality hardware, then you're good to go. We even did the old, "Let's see if I can stand on them" routine and they passed with flying colors. BTW, I'm 6'2" and 220 and it felt solid as all get out. For good measure, we went ahead and installed the screws that were included to attach the tube fenders to the trimmed originals so we didn't have all the holes leaving it look unfinished.
So at this point I liked the openness and ease of access this offered. However, with winter in the high country coming on, I decided that I really didn't want all the mud, snow, sand, and Colorado's famous "Ice Slicer" (made of granular salt and magnesium chloride) to be thrown up on the engine any more than it was prior to the change. So after searching the net for ideas, I put my thinking cap on and came up with this.
Flexible rubber engine bay shields - I picked up a sheet of 1/8" thick closed cell neoprene rubber off of Ebay. It was 36" wide X 72" long and ran me around $40 including shipping. Then I bought some 1" X 1/8" X 36" aluminum bar stock off of Ebay as well. I bought 4 pieces for under $20 delivered.
Making the shields is pretty straight forward. I worked on the passenger side first because there wasn't as much to work around, i.e. the charcoal canister and wiper fluid bottle. I found a nut and bolt sticking out of the firewall near the top. I measured from the bolt to the radiator shroud to get a rough dimension. I then drilled a 1/4" hole in the end of the bar stock about 3/4" from the one end. I drilled an 1/8" hole on the other end about 1/2" from the end. I needed to put a right angle into the end where it would attach to the firewall on the bolt that I was using, so I put it in the vise and bent it to a little less than 90 degrees. I did several test fits until I had the angle just right so it would sit flush on the firewall and on the shroud.
I rough cut the rubber about 1/2" shorter than the bar stock (about 35") and about 18" in width. Holding it in place, I marked a few areas that needed trimming so it would fall into place much like hanging a curtain. Using galvanized self-tapping screws, I attached the rubber to the bar stock about every 4" or so. Once I had the rubber attached to the bar, I ground off the protruding screws almost flush with the aluminum so I wouldn't get cut up if I accidentally brushed my hand or arm on it while working in the engine compartment. Then it was as simple as removing the nut off of the bolt sticking out of the firewall, putting the bent end with the pre-drilled hole over it and reattaching the nut. Then for the other end, I just used another galvanized self-tapper and attached it to the radiator shroud. There was no worry about drilling through there since it's mostly a cavity for the headlights. Then I held the front bottom of the rubber against the frame and attached it with another screw. There was no need to attach the bottom nearest the firewall as it just fell into place nicely. If I find that it flaps in the wind or creates any other annoyance, I can always make an "L" bracket out of the aluminum and attach it that way.
The drivers side took a little more finesse since I had to work around the charcoal canister and the washer fluid bottle that had been relocated because of the removal of the inner fender well. All that amounted to was cutting the corner of the rubber in a curved fashion to go around the bottles. There was another nut and bolt protruding from the firewall allowing for the mounting of that end, and I attached the front of it with another screw to that side of the shroud. The pictures below should be pretty self-explanitory. I found this to be an inexpensive, simple and hopefully, a very effective mod. Hopefully this helps out someone else who's had the same concerns after switching out your fenders.
Drivers side exterior
Drivers side interior
Passenger side exterior
Passenger side interior