Opinions on Single exhaust for v8

[danny]

I’ve been running dual exhaust on EBs for over 25 years . I love the sound of duals but I have been fighting fuel vapor lock for many years . I was thinking of going with a 2 into 1 to a magnaflow muffler. I have a mild build 289 and in process putting on a AX-15 . I like the fact that it will only run down the passenger side and free up space on the drivers side . Any recommendations?

 

[Yeller]

performance wise you are not giving anything up.

I believe with today's fuels; vapor lock is a fact of life with a carburetor. The boiling point is just too low.

 

[danny]

I have wrapped fuel
Lines and relocated , still vapor lock mostly on hot summer days here in NC .

 

[Soylent]

I have that setup on my 69 with a 302(6) crate, ax15 and like the sound and performance. Haven’t run a dual to compare.

 

[danny]

I have that setup on my 69 with a 302(6) crate, ax15 and like the sound and performance. Haven’t run a dual to compare.

Are you running shorty headers or full length? I am thinking of building my own exhaust with stainless fittings and my Tig welder . Just wondering if the crossover will work with long tube headers

 

[Soylent]

Mine are shorties and cross over at the bell housing iirc. Will snap a pic when it’s light out

 

[danny]

Mine are shorties and cross over at the bell housing iirc. Will snap a pic when it’s light out

I would like to see pictures your set up , thx !

 

[Brush Hog]

Have an old mild 302 in my 73 with a edelbrock avs2 carb. Went from long tubes and true duals to duff’s 2 into 1 about a year ago. One of best changes I’ve made. Great sound with magnaflow muffler. Less heat in cab and on fuel lines. More room underneath to work on things. That pipe down drivers side was always a pain and way too close to fuel lines. I think it runs, drives and idles better with the shorties and 2-1 exhaust. Seat of pants dyno feels like more torque at low rpm. It idles quiet but has a nice rumble when you hit the skinny peddle. No drone either.

 

[DirtDonk]

You can cross over into a single with either short tubes or long tubes. Just that the long tubes need a little more thought as to where you want to cross over.
And this is where extra fittings come in handy as well. Most people may never have to remove the exhaust to get a transmission out or service a driveshaft. But adding fittings to remove a section of tubing does make that kind of stuff easier.
Same for running it under the oil pan actually. Many can get away with never removing an oil pan from the Bronco, or weasel it around even with the exhaust in place. But having a removable section, there would make it a whole lot easier.
Also, the way I see it, if you’re running larger tubing, the rearward crossover leaves a little more leeway. Whereas the bell housing/oil pan crossover benefits from smaller tubing.
And even though I’ve never heard reports of ultra high oil temperatures because of exhaust being there, if I were running 2 1/2 inch from the header to the other side, I’d probably wrap the section of tubing that crosses under the engine.

 

[Shimmy]

i have tom's long stainless header with a dual exhaust and no issues with vapor lock. maybe i'm lucky.

 

[badandy73]

Another vote for 2 into 1, cross over just *behind* the bellhousing. Running WH/ JBA shorties into a Magnaflow, exiting out the back passenger corner. Great tone and opens up a lot of room underneath routed to that side.

 

[danny]

can anyone post some pictures of the crossover section ?

 

[badandy73]

Here's mine with a 347/4R70W, edited my post above to say 'behind' not in front of the bellhousing. Didn't have enough coffee this morning before posting.

Well clear of the inspection cover and plug, but short of the front pan bolts. Sans front driveline; working through a clearance issue with the cross member for the 4R.

 

[hunter1]

Here's what I did. Sounds mild idling but when revved up gets a little throaty. I like it.

 

[serial car restorer]

Check out Duff's single exhaust. A full 2½" system, Magnaflow is one of the muffler options. I've got Duff's dual system laid out in the garage now, looks good.

2 into 1 Exhaust Configuration, 1966-75 Bronco | James Duff Inc.

Installation Note: Contents Includes: Options: Information Looking for an exhaust for your Early Bronco? This 2 into 1 system works great with several different muffler choices to suit all types of…

dufftuff.com

 

[Torkman66]

I built my 2 into 1. I have mid length headers. Here are some pics and a sound video running a magniflow. If you can mig weld and have a cutoff wheel, easy t build your own custom system.

I purchased this 2 into one pipe.

Every joint is welded together except for the joint that connects the muffler to Y pipe. I used a clamp there so the system can easiliy be removed in two sections or if the muffler needs to be replaced.

On ther drivers side up near the headers, I wrapped the brake and fuel lines with heat guards.

Here is a sound clip of the system.

 

[Soylent]

 

[nvrstuk]

IF and only IF you want to keep dual exhaust then run your fuel line inside your frame rail. NO heat issues, no vapor lock problems ever. We drive in 90-100deg temps all day. Got a local buddy that's done the same and we both ran Q-jets for over 25yrs each. Never an issue with vapor lock

 

[DirtDonk]

Or you can also run your duals down one side. Makes it just a tiny bit tighter over there, but there’s generally plenty of room on the passenger side.
Especially if you pick the right mufflers and don’t go over 2 1/2 inch tubing. Dual 3’s are still doable, but overkill, and certainly not needed for 90% of the Broncos out there. And it does make it look a little more filled up.

 

[ntsqd]

My best vapor-lock prevention success has been to run a TBI electric fuel pump at the tank (Walbro GSL395BX or equivelant). Those are roughly 20psi output. Then I use a bypassing type regulator placed as close to the carb as reasonably possible. Does require running a return line. Increasing the pressure in the supply line from the slight vacuum that a mech pump will have to the regulated pressure causes the boiling point of the fuel to go up just like it does with a pressure cap on coolant. By using a by-passing regulator instead of a dead-headed regulator (like the more typical Holley regulators of old) the fuel stays in motion. Any hot-spot in the supply line will have fuel moving past it rather than dwelling there. On the Bronc-up I have a 5.0 Explorer's PS cooler set up to be in the return line for additional insurance against vapor-lock. If you've ever touched a later model's fuel tank after a long drive you'll know why this might be a good idea.

I ran a single 3.0 system on a street car with a 302 in it. It was a mistake. For any reasonably streetable 289 or 302 a single 3" is too large, even if you go clear to the rear bumper like I did. Performance suffered and it droned BADLY. (It did sound wonderful at WOT!) I talked to a Flowmaster Engineer who knew his stuff about it one year at SEMA. He told me that the system actually made the exhaust louder! A single 2.75" would have kept the exhaust gas velocity up enough to prevent the "constructive interference" that the 3" tube allowed. And that a 2.5" tube would aid the low engine speed performance.
For truck type use with a 289 or 302 I would go no larger than a single 2.5" tube. Leave the single 3" tubes for the 351 & larger displacement engines.