Gas Tank Vs Muffler

Building a combo meal Jeep. The V6 exhaust fits well but the muffler lands below the under the seat tank. Probably a 3” or so gap. Heat shield? No issue? Never work? I know this is one of those impossible questions but what would you do?

 

Put the muffler between the tcase and the rear axle

 

I wouldn't for a minute consider a 3" gap safe.

 

This.

 

I ran a pair of turbo mufflers under the floor on both sides (yes, under the tank on the drivers side) for well over 20 years. There was no appreciable heat transfer to the fuel tank, but the tank sat on 1/2” spacers above the floor, mainly to keep the floor and tank from rusting. This helped somewhat with the lack of heat transfer. The floor around the gas pedal got so hot from the exhaust manifold I couldn’t drive barefoot. I had a 215 Buick, but similar to a Dauntless.
-Donny

 

I don't see the problem. I'm running about 1.5" gap and the fuel filler dribbles onto the tailpipe.
Make sure you have your rubber straps between the tank and the floor. Try to keep that gap roomy like 1/4" minimum. so you get a good layer of organic insulation packed in there. Pine needles, dirt etc.

A heat shield would be best if it is something like a plate that is attached to the top of the muffler.
Give it a half inch or 3/4" with air flow between the plate and floor. I've been running this before my 4.3, I did it first for the turbo f-134 back in 2009. No reason to change except it's old and my wife is not keen to "old jeep exhaust" as much as "old spice".

Anyway I'm looking at one 2.5" inlet / outlet muffler under the tank and piping it to the rear corner. I'll probably have a stainless heat shield as part of the exhaust hanger with a nerf bar but not a skid or anything solid.

This is all flexed out as far away as it gets.

 

This is where it is. The tail pipe comes out of the muffler and immediately got over the axle. The muffler is about 10" in front of the where the step brace panel (back of the gas tank) is. I will have a ~1/4" gap between the floor and the bottom of the tank. I have not put the tub on yet so the fuel lines have not been run. Maybe I will try it and add if there is a problem. It would be easy to do a heat shield right now access wise but I can already here it rattling in my mind.

 

1/4" in not enough space in any location due to the exhaust moving with the engine.

 

I was talking about the gap between the floor and the bottom of the gas tank. I think I will try this.

 

I did this on my 71 and it worked very well.