We're doing all this work so we can technically do a "muffler tuck"...

That's right, I'm officially declaring the first use of the phrase "muffler tuck", right here.

My son enjoys a low, and relatively quiet car, that's still fast. If you do a burnout and people can hear you a mile away... you're car is to loud and your inviting the law to have a good look at you. On his CRX, when it's low, there just isn't enough room under there to get a muffler and not have it hanging down below the rear bumper cover. So the goal was to cut out the tire well, keep the structure of the car intact and allow a LOT more room for a proper muffler. A good high end muffler, that can't be seen dangling out from under the car for the law to have a good look at. Tuck it up, nice and tidy, 3" exhaust all the way out the back, exiting in the stock location for the Rex. Hidden, stealth, behind the bumper cover.

Keep the car quiet and un-assuming, but still be able to rip it up when required without drawing excessive attention! With the room we are creating for a muffler we are also creating a LOT more room for new sway bar mounts and ideas. and possibly other suspension stuff down the road.

I'm not a body guy and this was our first attempt at this style of fabrication and It was a good time. By the time you get some seam sealer on this and a coat of paint, some undercoating and some carpet. It'll look factory. We're happy with how it turned out.

Start by pulling the bumper cover.


Get a bunch of materials together to protect your dash and glass from sparks. You're going to be welding in there. Cover them inside and out. No quicker way to ruin your glass than weld boogers and microscopic molten metal flying around in there. We used cardboard, tape, sheets, whatever we could find. We caught a corner of that sheet on fire.... We're planning on NOT telling my wife about that sheet.



Here's the bit we cut out. Weighs 9.62 pounds for those that have wondered about that kind of thing. All the metal work we did was done with 18 gauge (.048" thick). I like how firm it is, for this kind of application. It's easy to weld to, compared to thinner stuff like 24 gauge which is about 1/2 as thick as 18 and can be tough to MIG to as it's (.023"). If you're new to sheetmetal fab. try 18 gauge.


traced the shape of the tire well onto some cardboard for a pattern to connect the lower cross member to the new floor. and cut, welded and shaped metal together until I had the shape.



Then we put rosette holes in the part so it can be spot welded together and fabricated the filler panel.

Here it is mocked up. The copper colored little tubes are called Cleco's. They're used to hold panels together for alignment. If you don't have any in your garage, GET SOME. They are very useful for lot's of stuff. Pick up a bag of them in 1/8" and the pliers. Seriously good things to have around.

 

We cut a piece of 18 gauge for the new floor and tossed over the whole to mock everything up. Starting to look like something. Any gap where you see light in the photos, we finessed the metal to fill the gap before welding.



Everything is lined up, square and flat. So we started hitting the spot welds on the cross member filler piece.




Everything is lining up pretty well. We used a bead roller to roll a few structural lines on both panels. The filler piece and the new trunk floor.

 

At this point, Start hitting those spot welds. I like to do about every third one and work my way around a panel so it doesn't heat warp. Have somebody push the sheet metal tight against itself so the spot weld can hold everything tight. You don't want to see gaps. Pop out the grinder and take off the high spots. I don't grind them flush, leave some weld. The seam sealer, paint, carpet, undercoat pretty much take care of hiding any imperfections.

We heated and hammered the little angle piece on the rear of the car below the tail light area (4th pic in this group) to fill the deep contours in the stock body. IF you don't hammer those in a bit, you're going to have to get seam sealer about 1/2" thick and stuff it down there. We felt hammering the metal into the contours added strength as well and helped eliminate potential leaks. It looks rough in the pics but looks smooth and relatively factory in person. We got a little to aggressive with the hammering and didn't use enough heat and actually put a very small bow in new floor just where it meets the rear of the car in the center. You can't see it when there's carpet on it, but I can feel it. next time, more heat and hit softer.

Time for sealing, paint, undercoat.





The reflections make it look wavy, but it's flat.

 

Pics of sealing and paint coming in the next few days.

the pocket created between the new filler piece and what's left of the old tire well is not going to be covered with sheetmetal. We are leaving it as a pocket for some speakers we are planning to flush mount in the floor right there. Speaker magnets should fit down in there real nice while the covers fit flush on the floor. Built in sub enclosure.

 

Very nice work. I like the idea its inovative and solves a problem. Great JOB!!

 

Good job looking good, curious to see how it turns out, so are you just gonna do a custom exhaust to tuck it or what?

 

That's cool and all...but where will he put the spare tire now? I'm curious to see the custom speaker enclosure. That's a nice little pocket for it right there.

 

Pretty cool man. Whats done to his car? Any more pictures?

 

Never mind, a little searching did the trick. Cool build, when I finish my Iron Work school my Father and I plan on building a crx also, sweet **** man!

 

Boy it does't seem like much work just reading it in a forum..

 

great idea! nice fab work and execution as usual! i've often thought about tinning the back area, more so to do with swapping to a straight axle in the rear, but very similiar concept.

Do you think the integrity of that lower crossmember gets comprimised at all by this, not so much the side to side but the back and forth forces on it. i would almost think that adding some bracing from the lower crossmember near the lca's to the side "rails" would be a good idea.

what model bead roller are you using?

 

nice, that is pretty cool -- good idea

 

Yea, likely stainless pipe and muffler. Magnaflow has a few we are looking at with an 18" body that look like the right unit.

tire goes on the roof... You know, I've never seen a Honda with a Continental kit. That would be hilarious.

I was thinking that same thing. 3 days of work and tinkering reduced to 3 posts and 12 pictures.

Having done this now, I'm a lot less hesitant to do a straight axle conversion on something and tin the back end. I was thinking along the same lines you are about the difficulty. It's not so difficult as it is piddly and time consuming. Number 1 piece of advice. Don't weld anything until it's completely mocked up.

We talked about it and don't feel the crossmember strength has been compromised. It's still got a pile of triangulation from all the other sides. I saw a build thread where a guy was racing his car with JUST the cross member dangling down and no other structure on it. and it seemed to be holding up to road racing abuse. I wouldn't do it, but he made it work. I think because the back of the car is so light you can get away with a lot of things that might seem sketchy on a heavy car.

The entire rear of the car with driver only weighs 750-800 pounds. 70 of that is wheels and tires. sprung weight maybe 690-700. One "G" of corner force would put 700 pounds of side load on it, and that force goes dead sideways across the chassis through the crossmember in the direction it has the most structural integrity, side to side. The way the suspension is held, the crossmember can't really be twisted. Look at what a sled or 4-wheeler weighs and how spindly those suspension component structures are and how high off the ground those things land from. We are simply driving around, or sliding sideways in a parking lot now and then.

Bead roller is a MB, Mittler Brothers.

Thanks mang.

 

Very well done. I look forward to seeing the follow up with the exhaust done.

 

a lot cleaner than mine turned out. but i welded it around all the seams instead of spot welding.

 

Got it seam sealed up. This turned out to be more art than science. And as the case with most things, you get the hang of it on about the last 4 inches of it...

We used this 3m sealer. Body shop buddy said they use it. That was good enough for me. The one tube "barely" got all the seams. We had another buddy stop by and said they make a neat seam sealer that comes in a can, and you brush it on. personally, I'm thinking that would be a good one to try.

We no more than get it on there and are admiring our handiwork when we notice there's a good bit we now need to grind off for the roll bar pads... aint that how it goes.











Estimated location for the roll bar pad.

 

Any pics of the car sitting on the ground?

 

Wow this is pretty cool! what motor is in the car? any more pics of the car?

 

https://honda-tech.com/forums/honda-crx-ef-civic-1988-1991-3/montana-crx-build-thread-2812729/

 

Seam sealer can be a huge pain in the *** when welding try and get as much out as possible if you plan on welding it there. You could do the rear supports to the shock tower?

 

A+++ nice fab work

 

great job! I did this on my dsm so I could fit a water tank in the rear for my a2w. Turns out the gas tank bumped up where the spare tire bump was :/ stupid dsm haha.

 

Would have been a lot easier to just fab a bulkhead for the rear, put the muffler in there, and route it out the top of the hatch with a flap on it.

Nice work.

 

I always love seeing good sheet metal work! I am ready to see the finished product.

 

Looks good nice fabwork.