Cutting exhaust to fit gas tank under bed?
 

To start off I plan on running a custom exhaust down the road after I complete some more mods.

I have a Tanks inc tank that I am planning to put under the bed. I want to put it in between the frame rails so that I have a little room to run a bend and have the fuel filler in the fender.

My main question is can I cut the exhaust after the muffler to fit the tank in?
If I Put a tip on it to angle it down away from everything? Will it effect anything by cutting off about 3 feet of pipe?

Re: Cutting exhaust to fit gas tank under bed?
 

That's what I did when I installed a rear gas tank - cut off the tail pipes and installed turn-downs ahead of the rear axle. No problems, especially since the exhaust is exiting under the bed and not under the passenger compartment.

Re: Cutting exhaust to fit gas tank under bed?
 

some would have the pipe exit to the outside of the frame and channel back to the rear, thereby avoiding the tank altogether. the issue is the heat, possible hot carbon particles and also the oxides of nitrogen etc given off by the exhaust. the exhaust will usually rust everything downstream from it's outlet if possible. also, if idling for extended periods the fuel will heat up in the tank from the hot fumes. the less fuel in the tank the quicker it heats up.ensure you have a good vent yhat exits away from the exhaust exit area.
anyway, just, thoughts. lots of vehicles have midship exits and down turned pipes. sometimes that's all that works.

Re: Cutting exhaust to fit gas tank under bed?
 

Thank you that will probably be what I do then for a while.

Re: Cutting exhaust to fit gas tank under bed?
 

Thanks for your response. That's another thing I need to figure out, venting the tank. When reading up on it seems like people will buy vented caps, or add a vent to the tank itself. Do they do the same thing? Seems like it would be easier just to buy a vented cap then to try to modify the tank?

Re: Cutting exhaust to fit gas tank under bed?
 

if it were me i would vent the tank to a charcoal cannister mounted high enough so as not to worry about a siphon effect when you have a full tank, etc. plus use a vented cap. if you vent through a cap only ensure it allows air entry and exit.

Re: Cutting exhaust to fit gas tank under bed?
 

What exactly is a charcoal canister? Ive never heard of that before. Do i drill into the tank to run a hose out?

Re: Cutting exhaust to fit gas tank under bed?
 

it's that black cylinder looking thing under the hood of the 70's-80-'s vehicles that are carbed and don't have an evap system. the vapor are vented to, basically, a can of charcoal that captures the vapors/hydrocarbons around the outsides of the charcoal crystals. a small engine vacuum line draws across the charcoal and takes the particles back to the engine to be burnt rather than escape to the atmosphere (and make your hotrod smell like raw fuel).
google it for more info on how it works and how the vacuum system is hooked up.

Re: Cutting exhaust to fit gas tank under bed?
 

I've run a lot of exhaust systems the way you're describing, no issues other than noise in the cab. Currently my 50's exhaust runs out both sides where the rear fender and running boards connect.

Re: Cutting exhaust to fit gas tank under bed?
 

Thanks I will definitely look into that.

Re: Cutting exhaust to fit gas tank under bed?
 

Thanks, looks like I will be cutting it off so that I can install my tank later this week.

Re: Cutting exhaust to fit gas tank under bed?
 

Unless you have some real quiet mufflers the noise level and concussion drone running down the road for any length of time can really get to you or at least it does me.

Add to that in heavy slow traffic like a long line going into a car show the exhaust wants to get inside the cab from below.

I've run several trucks with the exaust exiting in front of the rear tire and the only issues with that are again there can be a lot of extra noise plus the exhaust may cause you to need to do more cleaning on the rear wheels and tires. You don't get that continual drone of the exhaust exiting under the rig though.

Re: Cutting exhaust to fit gas tank under bed?
 

The exhaust outlets are still more than 3 feet behind the cab - that's a lot more distance from the passenger compartment than your average coupe, sedan or wagon. Beats the heck out of routing exhaust close to the gas tank and/or having to construct heat shields to prevent explosions. And at car shows your biggest exhaust problem will be the guy's rear-exit tailpipes AHEAD of you filling your cab with fumes, lol! ;-)

Re: Cutting exhaust to fit gas tank under bed?
 

It's still going to be loud in the cab. Some guys like that, I got tired of it in a hurry...

Re: Cutting exhaust to fit gas tank under bed?
 

Mine before and after. If there was an increase in volume I never noticed it.

Re: Cutting exhaust to fit gas tank under bed?
 

Reminds me of the gear drive I had in my V-8 S-10, it sounded cool for about 20 minutes. LOL

Re: Cutting exhaust to fit gas tank under bed?
 

I have glasspacks with exhaust vented down like previous poster. Oddly the drone noise only is noticeable when cruising at 50+ with 700r4 manually switched into OD. May look at venting out at ends of running boards but not sure it would be any better.

Re: Cutting exhaust to fit gas tank under bed?
 

That is exactly what I was saying in my post. If you have loud or somewhat loud exhaust that exits under the rig before the axle it drums inside the cab when you go down the highway at road speed and can be loud and annoying in town.

The main thing here is that we are suggesting running pipes out from under to the rig to exit out past the body or running boards. That isn't hard nor is it expensive and it makes a huge difference. Not as good as having the pipes run back and exit behind the rear wheels somewhere but it gets any fumes out from under the truck and gets a big part of the noise and drumming out from under the truck Then you can have fun hearing your pipes echo off the Johnson barriers on the highway to boot.

Re: Cutting exhaust to fit gas tank under bed?
 

Somebody gave me a "quiet" gear drive, and after about 6 months, I took it out and gave it back LOL

Re: Cutting exhaust to fit gas tank under bed?
 

personally I like to enjoy the ride and conversation or music, not the noise or the fumes. when I am behind or next to one of those noisy diesel monster trucks I always change lanes before a light so I can miss the stink and hear the passenger and/or the stereo. funny how those guys think it is funny to drown the guy next to them though. especially if it is a rag top. I don't get it but thats just me. same for the old hotrod thats dripping fuel from the tail pipe. I admire from a distance, I don't need to smell it to appreciate it. again, just my opinion. just remember the carbon monoxide levels that can be present in the cab when sitting at a light or drawn in when driving or whatever. the further back the exhaust dumps are the better for more than drone, heat and rust formation.

Re: Cutting exhaust to fit gas tank under bed?
 

This is what I was looking for.
When I rebuilt my truck the first time back in the 80's, I had the exhaust stop just before the axle. At certain rmp's the drone was unbearable.

Re: Cutting exhaust to fit gas tank under bed?
 

My 72s exhaust cuts out right before the rear axle and just dumps under the truck. No real drone issues but I do get exhaust back into the cab. No problems with the blazer tank between the frame rails either but it does have a skid plate.

Re: Cutting exhaust to fit gas tank under bed?
 

Went from under bed to out back. Flat miserable with under bed and neither passengers or I could stand the drone. Sounded like being in a empty oil drum. Now its wonderful and sound is fantastic!

Re: Cutting exhaust to fit gas tank under bed?
 

Vents cap or otherwise are to let air in to replace the gas that goes out. They are not only to let vapors out if the car is sitting.

A none vented cap on a tank that requires a vented cap won't work unless you add a vent to the tank. Once the fuel pump draws enough fuel out of the tank it creates a vacuum inside the tank that the fuel pump cannot overcome.

Re: Cutting exhaust to fit gas tank under bed?
 

Just my 2 cents about not running the pipes all the way out back. I remember some of the 50's cars that had exhaust pipes running through the chrome bumper. If the owners never fixed their rusted out tailpipes the oxides would rust all the metal away from the bumper area there and all that would be left is the hard chrome plating. Never forgot that. It's like cigarette smoke, I think it's bad for your body. I bought a plastic Blazer tank years ago that fits between the frame rails. I have lately seen some new frame mount tanks that are mounted in the C-channel and I don't think they considered that the frame flexes all the time. I don't know if anyone has ever mentioned that the 67-72 tanks are actually part of the cab structure strength.