New exhaust with M1A1

[lewain]

I finally pulled the trigger on the M1A1 tank and got it installed. I have dual exhaust with exit behind rear tires. I had to cut off my exhaust on the driver side too clear the j hook hanger.
I have been waiting for new exhaust until I installed the M1A1 tank to work around the hangers.
I went to have an exhaust system installed today and the guy wouldn’t do it because he said that he smelled fuel at my auxiliary tank. I didn’t smell it.
So I guess that I am going with an exhaust kit. What kit would you recommend? I have 351w and would like to keep true dual. I would like to tone it down a bit. Not church quiet, but toned down. I think that I like the magnaflow 60 maybe. What are your thoughts? No headers.

 

[JB Fab]

How about finding a new exhaust guy?

 

[serial car restorer]

I installed a kit from Duff on my '69. Numerous options including 7 different mufflers and 2 tailpipe angles. Pipe is 2¼" so a bit easier to make fit than some of the 2½" I saw. I'm pleased with it, overall.

https://dufftuff.com/product/custom...6-75-bronco-config/#manifold-header-selection

 

[gnpenning]

Did the exhaust guy have it up in the air when he smelled gas? Being under the rig or getting your head close to the aux tank can make a difference. Gas fumes are heavier than air. You should be able to get a flashlight and look for the tell tell signs of a fuel leak on your aux tank through the wheel opening.

Whichever way you go, take a minute and verify you don't have a leak. It wouldn't be the first one to leak. More than a few people have ran into sending unit O rings that seep. We don't want to hear about you having a fire. Peace of mind is a good thing.

 

[lewain]

Did the exhaust guy have it up in the air when he smelled gas? Being under the rig or getting your head close to the aux tank can make a difference. Gas fumes are heavier than air. You should be able to get a flashlight and look for the tell tell signs of a fuel leak on your aux tank through the wheel opening.

Whichever way you go, take a minute and verify you don't have a leak. It wouldn't be the first one to leak. More than a few people have ran into sending unit O rings that seep. We don't want to hear about you having a fire. Peace of mind is a good thing.

We did have it up in the air. I don’t believe that my aux tank is leaking. Believe me, I have delt with leaks in the past.
I am thinking that he may have caught a whiff from the canister.

 

[Shimmy]

from what i've seen on the forum, you can either modify those j hook mounts or you'll need to find another exhaust shop that'll fab your pipes around the M1A1. nothing off the shelf fits without mods. i have the Duff dual exhaust and originally bought the M1A1. you'll need to modify/bend the over axle pipe on back to fit. i ended up selling the M1A1 and getting the LC gas tank. not because the M1 didn't fit... i just wanted the LC tank really bad. hahaha

here's another thread on the matter
https://classicbroncos.com/forums/t...th-m1a1-tank-and-dual-exhaust-routing.326213/

EDIT: just realized you're asking about mufflers? i personally like the borla mufflers. nice tone and quiet enough i can hear my family talk while driving.

 

[gnpenning]

We did have it up in the air. I don’t believe that my aux tank is leaking. Believe me, I have delt with leaks in the past.
I am thinking that he may have caught a whiff from the canister.

Okay. I'm a trust but verify guy. Only takes a minute. Probably longer to get a light. Either way, you will have to make a few adjustments to make your exhaust work. Mufflers are like women, some are noisyer than others. Pick your level.

Please don't say that to your wife.

 

[lewain]

So, I have ordered the exhaust from James Duff and I will have my muffler shop install. By letting them install they can do whatever tweaking may be needed.
I have also removed my auxiliary tank to eliminate any fuel smells. I have found that the “O” ring around the tanks vent that goes to the charcoal canister is deteriorated. My question now is, I see no need for this vent. Can’t I just plug that and move on? There is no vent attachment on my new M1A1 tank.

 

[jamesroney]

So, I have ordered the exhaust from James Duff and I will have my muffler shop install. By letting them install they can do whatever tweaking may be needed.
I have also removed my auxiliary tank to eliminate any fuel smells. I have found that the “O” ring around the tanks vent that goes to the charcoal canister is deteriorated. My question now is, I see no need for this vent. Can’t I just plug that and move on? There is no vent attachment on my new M1A1 tank.

How is your M1A1 tank vented?

The sender / delivery configuration of the M1A1 tank is a disaster. You simply cannot use the vent port to vent the tank. You will notice that the vent port is about 2 inches lower than the fill level of the tank. This fills the vent port with liquid fuel, and then when the tank gets warm (because you put a recirculating heater in it called a "fuel pump") the air volume expands and pukes the liquid fuel into the evap can.

So don't use that vent location. (ever.) You MUST drill a new vent location in the fill neck and port that to your evap can. Otherwise your garage will stink forever. And of course your evap can will fill with fuel. And you muffler shop guy will run screaming...

(and no, there is no better tank out there, and yes, I do run one. And I love mine, but I did have to "fix" it.)

 

[jamesroney]

So, I have ordered the exhaust from James Duff and I will have my muffler shop install. By letting them install they can do whatever tweaking may be needed.
I have also removed my auxiliary tank to eliminate any fuel smells. I have found that the “O” ring around the tanks vent that goes to the charcoal canister is deteriorated. My question now is, I see no need for this vent. Can’t I just plug that and move on? There is no vent attachment on my new M1A1 tank.

Beware of muffler shop installers. There is a complex chain of communication between the customer (you) and the salesman, cashier, muffler shop owner, shop foreman, and the technician. (Sometimes that all the same human)

Every muffler shop that I have ever "unleashed" on my Bronco has at some point done something to disappoint me. It's usually silly stuff that is easily re-worked, or easily mitigated. But it drives me insane. So watch out for hangers, straps, welded bolts, and cheapo $5.00 brackets. You are going to spend $1K on an exhaust. Make sure that it meets your expectations. Inspect the installation while it is on the rack. Look for bad welds, funky hangers, bolts welded to your frame, and the ability to access your fuel tank strap bolts. Duff does a GREAT job with their kit...but it has to be installed right.

You are destined to be disappointed with the gas tank strap, skid plate hangar, J-bolt location, and your exhaust. I have never successfully "tweaked" a path that makes me happy. In ALL cases, I have modified the J-bolt configuration. If you can't see a path to success, your muffler shop installer certainly won't.

 

[lewain]

How is your M1A1 tank vented?

The sender / delivery configuration of the M1A1 tank is a disaster. You simply cannot use the vent port to vent the tank. You will notice that the vent port is about 2 inches lower than the fill level of the tank. This fills the vent port with liquid fuel, and then when the tank gets warm (because you put a recirculating heater in it called a "fuel pump") the air volume expands and pukes the liquid fuel into the evap can.

So don't use that vent location. (ever.) You MUST drill a new vent location in the fill neck and port that to your evap can. Otherwise your garage will stink forever. And of course your evap can will fill with fuel. And you muffler shop guy will run screaming...

(and no, there is no better tank out there, and yes, I do run one. And I love mine, but I did have to "fix" it.)

I am running a 351w with a stock carburetor with a vented gas cap.
So far no worries.

 

[lewain]

Beware of muffler shop installers. There is a complex chain of communication between the customer (you) and the salesman, cashier, muffler shop owner, shop foreman, and the technician. (Sometimes that all the same human)

Every muffler shop that I have ever "unleashed" on my Bronco has at some point done something to disappoint me. It's usually silly stuff that is easily re-worked, or easily mitigated. But it drives me insane. So watch out for hangers, straps, welded bolts, and cheapo $5.00 brackets. You are going to spend $1K on an exhaust. Make sure that it meets your expectations. Inspect the installation while it is on the rack. Look for bad welds, funky hangers, bolts welded to your frame, and the ability to access your fuel tank strap bolts. Duff does a GREAT job with their kit...but it has to be installed right.

You are destined to be disappointed with the gas tank strap, skid plate hangar, J-bolt location, and your exhaust. I have never successfully "tweaked" a path that makes me happy. In ALL cases, I have modified the J-bolt configuration. If you can't see a path to success, your muffler shop installer certainly won't.

I plan to be there with the installer and hopefully we get everything worked out.

 

[lewain]

How is your M1A1 tank vented?

The sender / delivery configuration of the M1A1 tank is a disaster. You simply cannot use the vent port to vent the tank. You will notice that the vent port is about 2 inches lower than the fill level of the tank. This fills the vent port with liquid fuel, and then when the tank gets warm (because you put a recirculating heater in it called a "fuel pump") the air volume expands and pukes the liquid fuel into the evap can.

So don't use that vent location. (ever.) You MUST drill a new vent location in the fill neck and port that to your evap can. Otherwise your garage will stink forever. And of course your evap can will fill with fuel. And you muffler shop guy will run screaming...

(and no, there is no better tank out there, and yes, I do run one. And I love mine, but I did have to "fix" it.)

Am I too assume that I should keep my charcoal canister and all connections intact? This is the first that I have heard of anyone drilling a hole in their M1A1 tank!

 

[jamesroney]

Am I too assume that I should keep my charcoal canister and all connections intact? This is the first that I have heard of anyone drilling a hole in their M1A1 tank!

A fill neck is NOT an "M1A1 tank" I have never drilled the M1A1 tank. (although I've drilled plenty of NWF tanks...) Nobody is drilling a hole in the tank.

The logical location for the vent is in a location HIGHER that the liquid level line. That puts it in the fill neck.

 

[lewain]

A fill neck is NOT an "M1A1 tank" I have never drilled the M1A1 tank. (although I've drilled plenty of NWF tanks...) Nobody is drilling a hole in the tank.

The logical location for the vent is in a location HIGHER that the liquid level line. That puts it in the fill neck.

O.k., back to my original question, I want to eliminate the vent on my auxiliary tank. I am not worried about the M1A1.

 

[Oldtimer]

I have found that the “O” ring around the tanks vent that goes to the charcoal canister is deteriorated. My question now is, I see no need for this vent. Can’t I just plug that and move on?

76 Bronco main and aux tank vent system has no O-rings? Just hard lines, rubber hoses, and hose clamps.

 

[lewain]

76 Bronco main and aux tank vent system has no O-rings? Just hard lines, rubber hoses, and hose clamps.

View attachment 952942

View attachment 952943

On my auxiliary tank #9002 there is a 1/4” barbed nipple where the hose #9170 connects. That nipple can be unscrewed and it has an “o” ring around it where it screws into the tank. That “o” ring has deteriorated and weeps.
I have still not gotten my question answered!

 

[lewain]

On my auxiliary tank #9002 there is a 1/4” barbed nipple where the hose #9170 connects. That nipple can be unscrewed and it has an “o” ring around it where it screws into the tank. That “o” ring has deteriorated and weeps.
I have still not gotten my question answered!

I just noticed that #9170 goes too the fuel fill vent. But, there is a nipple next too that for emissions.

 

[Oldtimer]

Even if you replace the barbed nipple with a plug, you still need to replace the O-ring. The vent going to the fill neck will allow you to fill the tank, so if you went to a vented cap you could eliminate the tank vent line to the charcoal canister, and smell gas fumes when you park in garage.

 

[DirtDonk]

And since many have had an issue putting vented caps in a non-vented cap application, what caps did you use?
Got part numbers? The "reach" on the tangs is different between late '70 and later, and early '70 and prior year filler necks, so they don't just swap over. Unless you've found the right cap to do this?
If so, let us know.

Paul