Exhaust vs fuel lines

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SkylinePCG
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Exhaust vs fuel lines

Post by SkylinePCG »

Finished a TBI conversion and ran a feed line across underside of the body.

Then got a quote for a stainless exhaust of $2k.

Lucky for me, I don’t have $2k for that. So instead I got a Y, some 2.25,” and some 3” in straight, 30 and 45 degree bends, as well as a handful of clamps and a 22” muffler.

It’s not hung yet, but it’s sitting where I think I like it. But I’ve never done this before, and wanted some 2nd opinions before it goes “permanent.”

My biggest concern is radiant heat in proximity to the fuel lines. Here’s a few pics. I’m all ears.
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tgreese
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Re: Exhaust vs fuel lines

Post by tgreese »

There's no place for the fuel pump ahead of the fuel tank? Seems like you are creating a problem by running the flexible line back to the rear axle cross-member and then forward.

Year/model/equipmewnt? Has the Corporate axle, so it's an '80 or newer.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
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SkylinePCG
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Re: Exhaust vs fuel lines

Post by SkylinePCG »

It’s an 80; 360/727/219/d44/amc20

The pump is on the crossmember for a couple reasons:
-no room in the frame rail with the fuel tank installed.
-if I did shoehorn it in there, the fuel tank would have to come back down to service the pump.
-the pumps rated for enough lift to be a little above the tank, and being both accessible and protected was accommodated with that spot on the crossmember.
-the feed lines route starts that way because the fuel level sender points that direction on top of the tank,
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tgreese
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Re: Exhaust vs fuel lines

Post by tgreese »

If you insist on the current location, I'd suggest 1) replace the plastic-body fuel filter with an aluminum one 2) long runs of rubber hose are a source of car fires - BTDT, not my car but personal experience 3) replace rubber lines with steel except for short lengths to connect components 4) heat shield of steel or aluminum will greatly reduce the radiant heating on all components; make the air gap as large as possible on both sides 5) suggest you run the fuel line parallel to the frame, make a right angle and parallel to the cross-member, providing maximum separation between the fuel lines and the exhaust; follow the route of the brake lines.

Really, running a rubber hose above the exhaust pipe will cause a catastrophic fire and burn your Jeep to the ground. Dangerous for passengers, you and your wallet. Total loss. BTDT.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.

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SkylinePCG
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Re: Exhaust vs fuel lines

Post by SkylinePCG »

Good call on the hard lines. That length is the only non NiCopp except for a few inches by the engine and it went in long before the exhaust. Made more sense then but there’s plenty of 3/8 left to remedy what you pointed out.
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Harry Dawg
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Re: Exhaust vs fuel lines

Post by Harry Dawg »

Second on hard lines. I replaced all of my lines for cheap using this Amazon special.

https://www.amazon.com/Stainless-Steel- ... 117&sr=8-3
1968 J3500 - 1985 CJ7 - 1998 Grand Cherokee 5.9 Liter Limited - 2006 Grand Cherokee Limited
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sierrablue
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Re: Exhaust vs fuel lines

Post by sierrablue »

Looks like you have plenty of space between the line and the exhaust. And yeah hard lines are a must.

tgreese, why the aluminum filter? You can't see in it when it won't start, and also aluminum is going to transfer the heat to the gas WAY faster than plastic ever could. So wouldn't the aluminum be the wrong way to go?
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tgreese
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Re: Exhaust vs fuel lines

Post by tgreese »

I would eliminate the filter entirely. There is a screen in the fuel tank to protect the pump. In-tank electric fuel pumps only run a screen, and they survive fine. Plus an '80 has a plastic tank and there should be no rust or other junk in the tank to foul the pump.

You can get filters that are fine on the high pressure side; no need to put a filter before the pump. I'd think that an electric pump would be much more tolerant of a filter on the high pressure side than the low pressure side. Example: https://www.rockauto.com/en/catalog/vol ... ilter,6200

Heat transfer to the fuel would be way down my list with this setup. My main concern would be the plastic filter cracking or melting and dumping gas. Broken fuel lines will cause a fire. The plasticizers in plastic are volatile and come out of plastic with age; that's why old plastics parts are brittle. Heat accelerates this aging. An aluminum filter would be safer than a plastic filter.

If you worry about heat transfer, fit heat shields. A plain sheet of steel between the exhaust pipe and the fuel lines will catch radiant heat and conduct it away. The body shell or frame would be an excellent heat sink. Convection will be directed away from the lines.

Lacking a suitable location ahead of the tank, I would move the pump and filter to outside the frame, far away from the exhaust. I would make a bracket to mount the pump on the frame rail outside, and add a skid plate to protect it. The skid plate could also hide the pump. Easy access, and no worries about exhaust heat.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
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SkylinePCG
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Re: Exhaust vs fuel lines

Post by SkylinePCG »

I can dig the metal vs plastic filter suggestion, but the placement between the tank and pump is a GM design, and a part of the TBI system this Jeeps conversion is based on. I feel like they do a pretty good job with their R&D, so I’m not interested in bucking that.

I do think there’s room to slide the pump/filter assembly toward the drivers side 4-6” to get it further away from the exhaust pipe. I like the central placement above the rear axle for the protection is affords. As this thing gets further along, an access panel will enclose it within the crossmember.

A NiCopp hardline has been flared, bent and fitted to replace the 24” stretch that’s currently there. After it’s installed, the only rubber left will be a few inches at the tank, the pump/filter section on the crossmember, and whats coming off the firewall to the throttle body.
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tgreese
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Re: Exhaust vs fuel lines

Post by tgreese »

SkylinePCG wrote: Sat Mar 18, 2023 7:10 pm ... the placement between the tank and pump is a GM design, and a part of the TBI system this Jeeps conversion is based on. ...
Did GM ever use an external pump like that with TBI? I thought they all used in-tank pumps with like 15 psi of pressure. I understood the inline pumps were used on Fords, with a low-pressure helper pump in the tank. What Howell gave you is like the Airtex E2000, and makes something like 60 psi. Not claiming it will be a problem - lots of TBI retrofit projects use that type of pump - instead wondering if you can conclude anything about the filter and pump etc.

https://www.rockauto.com/en/catalog/for ... +pump,6256

The Ford parts listing above also shows a strainer for the accompanying low-pressure pump, no filter.

Looking at the Ford filter, it's clear they place it on the high-pressure side (maybe it goes between the low pressure pump and the high pressure pump). GM uses a single pump in the tank, thus everywhere outside the tank is high pressure. Howell says this is like a '90ish Chevy pickup - look at the RockAuto listings for that vehicle.

https://www.rockauto.com/en/catalog/for ... ilter,6200
https://www.rockauto.com/en/catalog/che ... ilter,6200
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.

OldFarmTruck22
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Re: Exhaust vs fuel lines

Post by OldFarmTruck22 »

SkylinePCG wrote: Thu Mar 16, 2023 1:12 pm Finished a TBI conversion and ran a feed line across underside of the body.

Then got a quote for a stainless exhaust of $2k.

Lucky for me, I don’t have $2k for that. So instead I got a Y, some 2.25,” and some 3” in straight, 30 and 45 degree bends, as well as a handful of clamps and a 22” muffler.

It’s not hung yet, but it’s sitting where I think I like it. But I’ve never done this before, and wanted some 2nd opinions before it goes “permanent.”

My biggest concern is radiant heat in proximity to the fuel lines. Here’s a few pics. I’m all ears.
Just my .02 cents. First, nice work on the exhaust, it looks real good. One thing I WOULD do on the exhaust is extend that tailpipe longer so that it expells gasses out from under the truck. If you don't, you are going to have fumes inside the passenger compartment. A simple tail pipe end will got you outside the quarter panel. Trust me, it matters.
Next, get rid of that fuel filter, period. Not a place for a plastic fuel filter. Put one up front before your carb or fuel injection if you insist on plastic.
Next, unless you intend on only running your vehicle parked, standing still, for an hour or more at a time, you shouldn't have a problem with overheating the lines in the crossmember, but the OTHER line going directly above the exhaust system needs to be a hardline if you are serious about running it across there. AND I would buy a length of cloth heat shield tubing to run it through right above the exhaust pipes. That heat shield tubing works good. If you intend to drive the vehicle down the road and shut it off after you get there ... you should not have made enough 'heat' to melt anything on the crossmember location.
P.S. get rid of that filter in that location.
78 FSJ AMC 360 Quadratrac

letank
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Re: Exhaust vs fuel lines

Post by letank »

78 with quadratrac, I mounted my fuel pump on the left side frame rail in front of the QT, no EFI, only carb!

Image

here is a better one

Image
Michel
74 wag (349 Kmiles... parked, next step is a rust free body)
85 Gwag (229 Kmiles... the running test lab)

Topic author
SkylinePCG
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Re: Exhaust vs fuel lines

Post by SkylinePCG »

tgreese- now that you mention it, I think it is a ford pump and it’s been a while, but I recall the gm tbi pumps to be inside the tank. Close guess on Howell, but I went with Hamilton and he’s been very helpful despite my slow progress. Looks like I need to root back through some of his literature and my old notes…

OFT22- good eye on the exhaust; I actually ran out of the angle I want to finish it with, and since it’s going to be a minute before I get it back together to really run it, I decided not to bother with a temporary placement of a different piece. But yes when I get one last 30, it should exit at or very near the stock location.

Good suggestion too on the heat sleeve. I coincidentally have a new roll of that and it’s been in a box waiting for probably 10 years just for this.

Letank- what pump is that? Looks more compact than the one I’ve got, and I’d prefer the location you’re using.

Topic author
SkylinePCG
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Re: Exhaust vs fuel lines

Post by SkylinePCG »

Carter P4070? Looks like it runs at a lower psi than the airtex e2000, but may still be enough for TBI. I’ll look into that because I like the placement.

letank
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Re: Exhaust vs fuel lines

Post by letank »

SkylinePCG wrote: Tue Mar 21, 2023 2:27 pm Carter P4070? Looks like it runs at a lower psi than the airtex e2000, but may still be enough for TBI. I’ll look into that because I like the placement.
Yes it is the carter P4070, 4 to 7 psi perfect for the carbureted engine. What the pict does not show is that it sticks a bit below the frame rail by a 1/4", the bullet connectors for the electrical output. I used pre-existing holes.
Michel
74 wag (349 Kmiles... parked, next step is a rust free body)
85 Gwag (229 Kmiles... the running test lab)

Topic author
SkylinePCG
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Re: Exhaust vs fuel lines

Post by SkylinePCG »

Little update: rerouted the lines. There’s minimal rubber now, just in the connection pieces. Everything else is heat-sleeved NiCopp, and none of that is above the exhaust. Filter is still in the system, but now it’s a steel wix. At some point I may go to the s10 blazer tank and its internal pump, but for now the external pump lives on the crossmember, 6” west of its original location. Thanks for all the suggestions back in March!
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