The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1947 - 1959 Chevrolet & GMC Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 12-31-2017, 08:33 PM   #1
72Mountaineer
Registered User
 
72Mountaineer's Avatar
 
Join Date: Oct 2010
Location: Where Mountaineers are free
Posts: 406
Exhaust under fuel tank

I've noticed a few builds in the custom mags where the builder has run the exhaust under the fuel tank when it is between the frame rail in the rear. I always thought that this was taboo, maybe even not allowed in some states where a safety inspection is required. Any thoughts?
72Mountaineer is offline   Reply With Quote
Old 01-01-2018, 01:48 AM   #2
Black_Sheep
Registered User
 
Black_Sheep's Avatar
 
Join Date: Jun 2017
Location: upper midwest
Posts: 1,129
Re: Exhaust under fuel tank

My 2 cents worth, from a service and maintenance perspective it's not very practical. Plus, it looks kind of hokey, like the builder didn't plan for exhaust. Same thing for tailpipes that go under the rear axle...
Black_Sheep is offline   Reply With Quote
Old 01-01-2018, 06:04 AM   #3
Jesse Z
Account Suspended
 
Join Date: Aug 2016
Location: Florida, USA
Posts: 290
Re: Exhaust under fuel tank

Lots of late-model cars run exhaust much nearer the gas tank than I'm comfortable with right from the factory.

Two words: Heat Shields
Jesse Z is offline   Reply With Quote
Old 01-01-2018, 12:53 PM   #4
whitedog76
Registered User
 
Join Date: Jan 2014
Location: Peoria, IL
Posts: 1,450
Re: Exhaust under fuel tank

Pretty much every car made runs the exhaust under the fuel tank. Even going back to the 70’s and 80’s. My 85 Dodge van had the exhaust running right next to the PLASTIC tank, just a thin shield between them.
whitedog76 is offline   Reply With Quote
Old 01-01-2018, 05:30 PM   #5
Donaldo
Registered User
 
Join Date: Sep 2013
Location: Morro Bay, California
Posts: 447
Re: Exhaust under fuel tank

Put a heat shield between the pipe and the tank.
Attached Images
 
__________________
Thanks, Don

http://www.donsbirds.com/pick-up
Donaldo is offline   Reply With Quote
Old 01-02-2018, 09:43 PM   #6
72Mountaineer
Registered User
 
72Mountaineer's Avatar
 
Join Date: Oct 2010
Location: Where Mountaineers are free
Posts: 406
Re: Exhaust under fuel tank

Most production cars and trucks have converters which take most of the heat out of the exhaust from there back, so I'm not thinking about a cat exhaust. Just trying to get a feel for things. Thanks.
72Mountaineer is offline   Reply With Quote
Old 01-02-2018, 10:00 PM   #7
mr48chev
Registered User
 
mr48chev's Avatar
 
Join Date: Jul 2007
Location: Toppenish, WA
Posts: 15,711
Re: Exhaust under fuel tank

I don't think the heat is as much of an issue as the inconvenience if you have to drop the tank, Never heard of a 58/60 something Impala or a Mustang catching fire because the muffler dude ran the pipes under the gas tank.

You almost have to arm wrestle the muffler shop guys here to have the tail piped end up straight out under the bumper on a truck rather than off to the side behind the rear tire. As many late models around here run canopies on the bed and people might ride in them they want the exhust out in the slip stream rather than straight out the back where it might roll right back into the bed of the truck.
__________________
Founding member of the too many projects, too little time and money club.

My ongoing truck projects:
48 Chev 3100 that will run a 292 Six.
71 GMC 2500 that is getting a Cad 500 transplant.
77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around.
mr48chev is offline   Reply With Quote
Old 01-03-2018, 09:53 AM   #8
1project2many
Registered User
 
Join Date: Mar 2012
Location: Lakes Region NH
Posts: 3,200
Re: Exhaust under fuel tank

Here's the NH rule for heat shields. It used to apply to all vehicles but I only see it in the bus section now.

"The exhaust system shall not pass within 12 inches of the fuel tank and its connection, or any flexible brake system hose, unless a heat baffle is used, in which case a minimum exhaust system separation of 1.5 inches shall be maintained to the fuel tank, its fittings and any flexible brake system hoses. The exhaust system may be less than 12 inches from the fuel tank on diesel powered buses."

With exhaust under a tank, even if nothing melts, the fuel can get very warm which can cause vapor leaks and fuel odors, can cause excess vapors to be drawn into the charcoal canister, and can cause spark knock. But if you think about vehicles using plastic tanks today vs metal from the past, I think the OEM's run exhaust remarkably close to the tank.
1project2many is offline   Reply With Quote
Old 01-07-2018, 08:29 PM   #9
my56chevytruck
Registered User
 
my56chevytruck's Avatar
 
Join Date: Feb 2016
Location: Hebron
Posts: 1,153
Re: Exhaust under fuel tank

I guess my street rod that I've had for 20+ years with the exhaust pipes running under the gas tank wouldn't be happy in NH. If you take the time and look at most street rods, hot rods, the exhaust pipes are running under the gas tank. If you can run the pipes away from the tank then do so.
__________________
RUBBER DOWN AND HIT THE ROAD!!!
1940 Ford Dlx Coupe
1969 Mach1
my56chevytruck is offline   Reply With Quote
Reply

Bookmarks


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 09:38 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com