How close it too close?

[davepl]

My exhaust was installed by the body shop long before I reassembled the truck (frameoff teardown). As a side-effect they didn't take into account the parking brake cables and the tank fuel line.

The plastic-coated parking brake cables, even after re-routing one side, are about an inch away (sideways) from the pipes.

The rubber section of fuel line that runs between the cab line and the frame line (it's there for flex, I imagine) is 1.5" above the exhaust pipe.

On the plus side, this is about mid-truck, so it's not just off the collectors or anything.

I wrapped each of these sections with DEI Titanium Exhaust wrap (woven from lava rock fibers!). It withstands 1800F direct and 2500F intermittent, but its really more about insulating the rubber hose for me.

Is an inch and a half air gap enough with an insulated pipe? I figure at idle when no air is moving its under very little load, and under a lot of load it'd have a lot of airflow. But it's really a SWAG.

I also added a reflective heat tube around the fuel line. So they're both insulated and now with about an inch air gap. And I suppose the fuel hose gets cooled by fuel, though not much at idle.

[El Campo]

Good question! Curious to see the responses on this one.

[davepl]

I wouldn't mind seeing how close they were from the factory. My exhaust isn't unreasonably high in the chassis, I don't think. If someone can measure or get a photo, I'd sleep better. Or worse. But at least I'd know.

[davepl]

No answers yet. Did the factory even run dual exhaust, and if so, how did they get the pipe through there while keeping it away from the rubber line?

[FirstOwner69]

Originally Posted by davepl

No answers yet. Did the factory even run dual exhaust, and if so, how did they get the pipe through there while keeping it away from the rubber line?

Only the big blocks such as yours had duals. The small block single pipes ran down the left side.

Most small block owners have probably converted to duals as I did. My right side is basically a mirror image of the left. I assume your leaf spring truck pipes would be the same to the rear of the crossmember that supports the driveshaft carrier bearing and that they are different from that point back. If that is correct, the pipes should run below both of those crossmembers. My right pipe is about 6" below the rubber line that connects the tank fuel line to the frame line.

Below are the best pictures I can find in my file. I've zoomed in for clarity. The red dot at the center right edge of the first picture is a cap on the fuel line. It can also be seen near the top of the second picture.

Regarding the parking brake cables... Mine are the originals (3/4 ton with TH400). As you can see in the pictures, they are not plastic coated. The Longhorns may have been different, but, other than length, I'd doubt it.

Jim

[71 super]

. It looks like yours is above the crossmember, the factory did not do that. I will snap pics of my bb truck in am for you.

[davepl]

It is - sort of through the crossmember actually. Would very much appreciate a photo!

[special-K]

The standard that exhaust shops go by is 1" minimal clearance on gas tanks,from my experience. I have Air Lifts on my K3500 and the exhaust passes about an inch from the passenger side bag. They did provide a light gauge aluminum heat shield to put on the pipe. But no problems with that. The further back the better due to cooling of gases

[71 super]

Dave this is very bad picture but hopefully you can see how low the factory dropped the exhaust under crossmember and it angles up and dog legs just past the mid cross member so it is never near the fuel line. Sorry for crappy pic the iPad and dark garage equals bad. Pipe drops off head pipe and basically runs parallel to frame til mid crossmember

[davepl]

Looks like my two options are new head pipes to drop it below the crossmember or to try to increase the clearance.

I did the latter today - loosened all the hangers and clamps and fought with it until I got about 2" (exclusive of the heat wrap and shielding).

SpecialK - when you said 1", was that for the metal line or near rubber? There usually is a section of rubber back at the tank on cars, so I'm not sure which you meant.

[davepl]

For what it's worth, I found this:

http://gibsonperformance.com/product...str_mnl_01.pdf

"MAKE SURE
YOU HAVE A MINIMUM
OF A 1” CLEARANCE ON
ALL PIPES FROM ALL
RUBBER BRAKE LINES,
TIRES, SHOCKS, FUEL
LINES, ETC. THEN
TIGHTEN ALL CLAMPS
AND HANGERS"

[special-K]

That's what I meant,and that's with no shield. Sounds like you have it?

[davepl]

If they're ok with 1" from rubber, I'm much better off than that. I wonder about using steel braided line instead. I could at the extreme transition from hard line double flare to AN, use braided line, then AN back to double-flare. A lot of work to flare in place, would require I drain the tank again. and if you mess up once there's no extra line coming out of the cab to "try again".

I wonder if there's a cheap remote sensor I could stick on the hose for a couple of weeks just to see what range it's operating in, then I'd know.