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Heat Shield needed near gas tank when re-routing exhaust?

The Butcher

The Butcher

1/2 ton status
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Texas. In a van, down by the river!
I just raised the bumpers on my '91 K5 with a 3" body lift. Now that they are raised I am ready to put on the dual exhaust. Going to be running dual Dynomax 2.5" inlet/outlet mufflers and put the exhaust out each side behind each rear tire. Now that the bumpers are moved up I want to raise the exhaust as well to cover up the now exposed rear spring hangers, and also to tuck the exhaust closer to the body.

Do you guys think I will need a heat shield around the pipe where it goes between the spring hangers and gas tank? As it sits currently, the pipe is 6" or so away from the gas tank, but if I tuck it between the two it will be only a few inches from the gas tank. I was thinking of using this as a heat shield:

http://www.jcwhitney.com/autoparts/...006315/N-200005084+111+1990+600012697/c-10614

Anyone have any suggestions as to whether that is needed and if it is a good idea? If I run the exhaust out the passenger side as well, what are the things I need to be concerned with as far as keeping the exhaust away from fuel lines, etc.? Thanks for your help.
 
You get alot of rain there in Texas? That was funny. Laugh damnit!! I'm thinkin that you could prolly get away with wrappin it with asbestos or whatever is the new fangled deal.
 
My exhaust is about 3 inches from the tank and never been a problem. It was like that when I bought it years ago.
 
scrappy88 said:
My exhaust is about 3 inches from the tank and never been a problem. It was like that when I bought it years ago.
Click to expand...

My truck is at the shop right now, so I could be off in my guesstimate on how far away the pipe is or will be from the tank. Is your pipe in the factory location, or was it moved for a custom exhaust? If it is in the factory position, then that is where mine would be. Moving it up between the spring hangers and tank would make it pretty close to the tank. Not sure if it is close enough to warrant concern, but it seems like a fairly bad place to put something REALLY hot.
 
It's in the factory spot, 3" single exhaust. Do you have the factory skid plate under the fuel tank? You could just attach a piece of sheet metal to that to wall off the side of the tank where the exhaust comes close.
 
scrappy88 said:
It's in the factory spot, 3" single exhaust. Do you have the factory skid plate under the fuel tank? You could just attach a piece of sheet metal to that to wall off the side of the tank where the exhaust comes close.
Click to expand...

I do have the fuel tank skid plate, so that is pretty much what I was thinking about doing if I didn't use the tubing from JCWhitney. How thick of a piece of sheet metal would be sufficient for that kind of thing? I assume that the metal helps dissapate the heat much like a heat sink or cooling fin instead of actually shielding the area like an insulator. Are my assumptions correct about that?
 
What is the shortest distance from the factory exhaust to the tank? I've been running a custom duals for many years with no problems. I did not realize just how close the exhaust is to the tank untill recently... 3in
 
Feel your exhaust after the truck has been running for awhile. I suspect you'll see that it's warm, but not hot enough to pose a hazard.
 
Thanks for the responses guys. The factory exhaust is obviously at an acceptable distance from the tank. My concern is that re-routing the exhaust to tuck it up under the body better now that I have a 3" bodylift will make it run too close to the tank. Once it has been re-routed it could be as close as 1" from the side of the gas tank. I'm just concerned that might be an issue. Do you guys think that it might not be that hot by the time it gets to the end of the tubes, thus a heat shield might not be needed?

Thanks.
 
Well, it's not like you can't see how hot the pipes get and make the determination yourself, right? I dunno what the ignition temp is for gas vapor, but I suspect the exhaust back that far won't be hot enough.

The thing to worry about is sparks. If the pipe rubs the tank or anything else, THAT would be cause for concern. Mount the exhaust solidly, not the cheapy plumbers strapping I see often.
 
My exhaust runs within 2" of the tank. Its not my favorite set-up, and I'll probably change it in the future, but for now that's where it is and it hasn't caused any problems (been that way for 1 1/2 years).
I did fab a heat shield for the fuel filter on the frame rail. The exhaust is about 4" from that. Again, I haven't had any problems, it just seemed like if there would be an issue, that's where it would be so I fixed it.
 
My pipes are less than an inch from my tank.They dont realy get that hot.

7638870-R1-005-1_1_edited.jpg
 
Thanks for the pic. That's exactly where I am thinking about putting the pipes. Then I'm going to turn them at a 90 degree angle just after the rear spring hanger to dump each side straight out. If I catch on fire, it's your fault! :D

It sure was nice of you to turn your truck over so I could get a better look at the pipes. :laugh:

Thanks for the input guys.

Butcher
 
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