Question on dual exhaust muffler orientation

[Rembrant]

Hi Folks,

I'm getting pretty close to where I have to order...or at least start planning on what to order for exhaust parts. I know dual mufflers will have to be mounted on their sides, and also side by side, on the RH side of the truck. That part is understood. Is there a common muffler in/out arrangement to use for this? Like center inlet offset outlet, or offset inlet and center outlet?

I see that full length header outlets hang pretty low in these trucks. If full length headers are installed, do most people run the pipes under the transmission cross-member? Or over?

If shorty headers are installed with duals, is it common to have the left side pipe cross to the right hand side right under the engine/bellhousing where the stock Y-pipe crossed?

I'm wanting to keep the exhaust in the stock routing, even if I do go with full a full dual set-up. And by stock routing, I mean stock as far as the muffler(s).

 

[Gary Lewis]

Good questions! And ones I'm curious about as well.

On the mufflers, I've been thinking of two different approaches:

• Staggered: Use two mufflers, turned on edge, but put one ahead of the other to make the pipes run as closely to each other as possible.

• Dual In/Dual Out: I'm going with Magnaflow mufflers, and they have two mufflers made into one, like this 5x8" model. I'm not sure that will be quiet enough for me, so I intend to call them and discuss things before I buy, but it is an option I'm considering. EDIT: I just found that they have a 5x11" model that should be quieter.

As for full length headers, I think Big Blue has one pipe over and one under the cross-member, but I'll look later.

NOTE: I edited this post to include another 2 in/2 out muffler from Magnaflow.

But I do think that with shorty headers the pipes run best in the factory location.

[Gary Lewis]

Good questions! And ones I'm curious about as well.

On the mufflers, I've been thinking of two different approaches:

• Staggered: Use two mufflers, turned on edge, but put one ahead of the other to make the pipes run as closely to each other as possible.

• Dual In/Dual Out: I'm going with Magnaflow mufflers, and they have two mufflers made into one, like this 5x8" model. I'm not sure that will be quiet enough for me, so I intend to call them and discuss things before I buy, but it is an option I'm considering. EDIT: I just found that they have a 5x11" model that should be quieter.

As for full length headers, I think Big Blue has one pipe over and one under the cross-member, but I'll look later.

NOTE: I edited this post to include another 2 in/2 out muffler from Magnaflow.

But I do think that with shorty headers the pipes run best in the factory location.

Just listened to this episode of Engine Masters where they tested straight pipes, H-pipes, and X-pipes. Cool episode, but the answer is that there's precious little to be had in the way of power gain with cross-overs. But apparently the sound changes more than the power - not the volume as much as the "quality" of the sound.

[Rembrant]

Just listened to this episode of Engine Masters where they tested straight pipes, H-pipes, and X-pipes. Cool episode, but the answer is that there's precious little to be had in the way of power gain with cross-overs. But apparently the sound changes more than the power - not the volume as much as the "quality" of the sound.

Excellent! Yes, I've watched this episode. I'm a Motor Trend on demand subscriber, so I've watched many of these. I was planning on an H-Pipe.

My problem is that when I removed the engine and trans, I took my Sawzall to the exhaust...all of it. With the exception of the muffler and tail pipe, it was all original 1984 stuff and had to go.

So, in a week or two I'll have my engine back, and I want to drop it and the trans all in there in one shot. What the heck do I do with the exhaust? Send the truck on a flat deck to an exhaust shop, or do something temporary with it, like install a cheap off-road Y-pipe and muffler so I can drive it and get everything set-up and running right.

If I order a couple mufflers and get a shop to bend duals for me, I need to know what inlet/outlet offset(s) to order.

[Gary Lewis]

Just listened to this episode of Engine Masters where they tested straight pipes, H-pipes, and X-pipes. Cool episode, but the answer is that there's precious little to be had in the way of power gain with cross-overs. But apparently the sound changes more than the power - not the volume as much as the "quality" of the sound.

Excellent! Yes, I've watched this episode. I'm a Motor Trend on demand subscriber, so I've watched many of these. I was planning on an H-Pipe.

My problem is that when I removed the engine and trans, I took my Sawzall to the exhaust...all of it. With the exception of the muffler and tail pipe, it was all original 1984 stuff and had to go.

So, in a week or two I'll have my engine back, and I want to drop it and the trans all in there in one shot. What the heck do I do with the exhaust? Send the truck on a flat deck to an exhaust shop, or do something temporary with it, like install a cheap off-road Y-pipe and muffler so I can drive it and get everything set-up and running right.

If I order a couple mufflers and get a shop to bend duals for me, I need to know what inlet/outlet offset(s) to order.

Most people use 2 1/2". That's what Big Blue has, so I'm pretty sure that would be quite adequate for a 302. And, looking at Magnaflow's mufflers it is either 2 1/2" or 3", so I'd go 2 1/2".

In fact, that's what I'm going to do on Big Blue. The 1990 half-truck (Huck) that I bought came with the full exhaust, but the pipes were cut right behind the X and just ahead of the glass pack mufflers. I'm done with glass packs, which is what is on Big Blue now, so will have someone run from the cut back and incorporate one or two Magnaflows, but otherwise duplicate the factory run.

I'm pretty sure I'll go with the 5x11 2-in/2-out Magnaflow given the reviews here. Those folks say all the right things - like "It's quieter than I had hopped. Louder than stock but really very quiet in the cab even when towing." Just what I'm looking for. And, by the way, these have an X-pipe incorporated internally, so there might not be a need for an H-pipe.

As for getting it to the muffler shop, you might check to see if they'll come and get it. I'm going to winch Big Blue on my trailer and take him down to the shop that way.

[Rembrant]

Most people use 2 1/2". That's what Big Blue has, so I'm pretty sure that would be quite adequate for a 302. And, looking at Magnaflow's mufflers it is either 2 1/2" or 3", so I'd go 2 1/2".

In fact, that's what I'm going to do on Big Blue. The 1990 half-truck (Huck) that I bought came with the full exhaust, but the pipes were cut right behind the X and just ahead of the glass pack mufflers. I'm done with glass packs, which is what is on Big Blue now, so will have someone run from the cut back and incorporate one or two Magnaflows, but otherwise duplicate the factory run.

I'm pretty sure I'll go with the 5x11 2-in/2-out Magnaflow given the reviews here. Those folks say all the right things - like "It's quieter than I had hopped. Louder than stock but really very quiet in the cab even when towing." Just what I'm looking for. And, by the way, these have an X-pipe incorporated internally, so there might not be a need for an H-pipe.

As for getting it to the muffler shop, you might check to see if they'll come and get it. I'm going to winch Big Blue on my trailer and take him down to the shop that way.

I think I'll mock up a fake muffler out of cardboard when I'm at work tomorrow, and then stick the cross-member back in temporarily and just see where the piping will land (approximately). That will tell me what muffler inlets/outlets to order...I think.

[85lebaront2]

I think I'll mock up a fake muffler out of cardboard when I'm at work tomorrow, and then stick the cross-member back in temporarily and just see where the piping will land (approximately). That will tell me what muffler inlets/outlets to order...I think.

The system I designed and had built for my 77 with the 390 Camper Special engine, was left side back over the suspension cross member, then cross under the C6 extension housing and into a Corvair Turbo muffler turned vertically. Right side back over the suspension cross member and into another Corvair Turbo muffler turned vertically. There was a short H connection right where the two sides came together. The left side muffler was in front of the right side so the pipes ran close together. The dual tailpipes ran down the right side, over the axle and out on a 45° angle just ahead of the bumper. That way they were clear with or without the pickup camper in.

[LARIAT 85]

Just listened to this episode of Engine Masters where they tested straight pipes, H-pipes, and X-pipes. Cool episode, but the answer is that there's precious little to be had in the way of power gain with cross-overs. But apparently the sound changes more than the power - not the volume as much as the "quality" of the sound.

I ran a true dual exhaust system (a separate exhaust pipe running from each header) on Lucille since about 2009. In 2014, a friend in the exhaust business convinced me to install a crossover pipe. It was explained to me that an H-pipe helps with low-end torque and produces a deeper, classic muscle car sound. The X-pipe helps more with top end horsepower and produces a raspier, modern exotic car sound. Since I have an old-school, full size truck with a 5.0/302, I thought an H-pipe would be more fitting. So I went ahead and did it, not really expecting much difference.

Boy, was I wrong. The H-pipe made a VERY noticeable difference in my truck! Driving away, I felt the difference immediately. Although throttle response was always excellent with this truck, the H-pipe greatly improved low end power; I actually felt the difference in the throttle. The engine seemed to "breathe" better, as in I could accelerate MUCH easier and faster with less throttle pressure than before. The improvement felt like I fixed a sticking brake, or like I shed 500 pounds off the truck!

An added bonus came after I got home and got out to inspect the H-pipe location with the truck at idle: the exhaust note is now deeper, much STRONGER. It now sounds like...a 5.0 Mustang! This really is one of the best mods I made to Lucille.

Here is a cool video demonstrating the difference in sound between an H-pipe and an X-pipe:

 

[Rembrant]

I ran a true dual exhaust system (a separate exhaust pipe running from each header) on Lucille since about 2009. In 2014, a friend in the exhaust business convinced me to install a crossover pipe. It was explained to me that an H-pipe helps with low-end torque and produces a deeper, classic muscle car sound. The X-pipe helps more with top end horsepower and produces a raspier, modern exotic car sound. Since I have an old-school, full size truck with a 5.0/302, I thought an H-pipe would be more fitting. So I went ahead and did it, not really expecting much difference.

Boy, was I wrong. The H-pipe made a VERY noticeable difference in my truck! Driving away, I felt the difference immediately. Although throttle response was always excellent with this truck, the H-pipe greatly improved low end power; I actually felt the difference in the throttle. The engine seemed to "breathe" better, as in I could accelerate MUCH easier and faster with less throttle pressure than before. The improvement felt like I fixed a sticking brake, or like I shed 500 pounds off the truck!

An added bonus came after I got home and got out to inspect the H-pipe location with the truck at idle: the exhaust note is now deeper, much STRONGER. It now sounds like...a 5.0 Mustang! This really is one of the best mods I made to Lucille.

Here is a cool video demonstrating the difference in sound between an H-pipe and an X-pipe:

Hey Lariat,

Do your pipes run under the transmission cross-member, or over?

Are your mufflers mounted vertical, side by side?

And another stupid question...after watching A LOT of 302 exhaust videos..

Does the HO firing order cam make the 302 sound different?

Suppose you had a mildly modified engine, and you changed nothing but the cam from the regular 302 firing order to the HO/351 firing order, same profile cam. Would they sound or perform different? Just curious.

[LARIAT 85]

Hey Lariat,

Do your pipes run under the transmission cross-member, or over?

Are your mufflers mounted vertical, side by side?

And another stupid question...after watching A LOT of 302 exhaust videos..

Does the HO firing order cam make the 302 sound different?

Suppose you had a mildly modified engine, and you changed nothing but the cam from the regular 302 firing order to the HO/351 firing order, same profile cam. Would they sound or perform different? Just curious.

Both of my exhaust pipes turn up and over the transmission cross member.

I have two Flowmaster mufflers, run vertical, side by side.

Lucille has a Comp Cams 31-230-3, which is the older (non-H.O.) firing order.

Before I chose a cam, I did lots of research on the topic of sound and performance on the standard firing order and the H.O. firing order. I have heard/read everything from the older firing order produces slightly more torque, to the newer firing order gives a slightly smoother idle and a deeper sound. Then something about the older firing order being harder on the crank, to the "H.O." firing order was simply a name given only because it was first used on the 1982 Mustang GT 5.0L "H.O." In 1982, Ford found that they could use their existing 1973 Torino 351 cam in the Mustang GT and simply change the firing order to make it work on the 5.0/302 engine. In other words, marketing hype.

I don't think there is much, if any, difference, because I have *never* seen a before/after test to prove it either way. The older firing order was used for a LONG time and on more vehicles - from the early 1960s well into the 1990s (except the Mustang 5.0) - so that is good enough for me.

My conclusion is that the distinctive "Mustang" sound has nothing to do with the "H.O" firing order, but comes from the specific cam profile and the use of a crossover pipe. The cam I have is very similar to the Ford Mustang "H.O." cam, except the ICL and LSA is adjusted to get better bottom end and a bit more lift.