Exhaust questions for boxes seem to be pretty common, so I've tried to gather up some of the usual basic info floating around. Please let me know if anything is wrong/should be added/your opinions. This is just stuff I remember/have done myself so I'm making it up as I go along. I'd just like to make a nice exhaust options write up once and for all.
So you want to upgrade the exhaust on your Box? Excellent. Here's some info to hopefully help you make a decision on what would be best for your own car.
The first and most basic upgrade, would be upgrading to factory duals. Factory duals are worth ~10hp over factory single exhaust.
Factory duals consist of: H-pipe, drivers side muffler, drivers side tailpipe, and additional hangers.
This is a 100% direct replacement, that requires little to no modifications. The hangers themselves changed in 89? so be aware if your using junkyard parts.
Next up is one of the must common questions. Will Mustang headers fit on my Box? Short answer: No. But why?
Let's look at the factory manifolds. These are all the same from 86? to 91 for 302's. Early 79-85 manifolds may be a touch different, and/or missing an o2 sensor hole.
These large cast iron beast are very heavy, and don't flow that great. They work excellent in a dumpster.
A nice upgrade to these, are 1990 Town Car tubular manifolds, commonly referred to as "Lincoln Logs".
These weigh significantly less then the cast iron manifolds, and also flow a touch better. They are also a 100% direct bolt on to your factory down pipes and require no modifications.
They also have another significant plus, and that is they can be used on GT40P cylinder heads. There is just enough room for the plug wires, but if you need to/want to retain your factory exhaust, these are your only options.
GT40P's with Lincoln Logs mocked up:
Next up is Mustang headers. These will not bolt to your factory down pipes. The collectors on the factory downpipes are too small, and just barley make contact with the headers, the angles aren't quite right, and the bolt holes do not line up. A few have "made it work", but in the end were unhappy. What else needs to be done to make Mustang headers work? We'll get to that in a second. Let's look at header options quick.
First up is factory Fox Body headers.
These work great for a modded lopo, or stock HO. You can often find these for very cheap/free, as Mustang guys upgrade to aftermarket. The only mods need for them to work (besides for the rest of the exhaust), is spacers for the brackets for the air box, dip stick tube, and possibly the smog stuff. Those same rules apply to nearly every aftermarket Mustang shorty header.
If your running GT40P's, you will need a "P" specific header, such as these FRPP ones.
Now, in order to run Mustang headers on your box, you will either have to have custom down pipes made, or run a Mustang H-pipe. Factory or aftermarket H-pipes follow the same rules pretty much. Nether fit that great, but can be made to work. A factory catted Mustang H-pipe will not work on a 90/91 as the one cat completely jams against the shift cable. It may work with some mods. You will also need either long wire 02 sensors, or extend the wires on your sensors. Mustangs have the 02 sensors in the H-pipe, as compared to the manifolds on boxes.
Here's a factory Box exhaust system compared to a factory Mustang system.
And an aftermarket Summit catless 2.5" H-pipe
************
This section I need your guys help on, I know some people run mustang extension pipes with pipe welded on, and others run s-10 midpipes. I don't know enough about either to comment on.
*************
As I mentioned, the Mustang H-pipe doesn't fit perfectly. I personally cut the ball flanges off the H-pipe. Make a notch on the pass side pipe which sits at a weird angle, and bend it straight and weld it up. Then I weld some straight pipe back to the mufflers. I have done this successfully on 2 cars now, and it tucks the exhaust up to almost factory levels.
Once you get to the mufflers, you can either dump the exhaust at the axle, or the most popular option is to add 2.5" Impala SS tailpipes. These are mandrel bent, and flow really, really good. As of now, the only place that still sells them is RockAuto. DynoMax 50417 and 50416 are the ones you want.
They require a little love to fit, but are the best pre-bent buy-able pieces. You will have to add extensions too them though.
As you can see, there isn't really a great option for us Box owners as far as aftermarket parts are concerned. Mustang parts work to an extent, as as of now are the best viable option IMO.
Some additional info,
Stock Explorer Manifolds:
Comparison pic:
So you want to upgrade the exhaust on your Box? Excellent. Here's some info to hopefully help you make a decision on what would be best for your own car.
The first and most basic upgrade, would be upgrading to factory duals. Factory duals are worth ~10hp over factory single exhaust.
Factory duals consist of: H-pipe, drivers side muffler, drivers side tailpipe, and additional hangers.
This is a 100% direct replacement, that requires little to no modifications. The hangers themselves changed in 89? so be aware if your using junkyard parts.
Next up is one of the must common questions. Will Mustang headers fit on my Box? Short answer: No. But why?
Let's look at the factory manifolds. These are all the same from 86? to 91 for 302's. Early 79-85 manifolds may be a touch different, and/or missing an o2 sensor hole.
These large cast iron beast are very heavy, and don't flow that great. They work excellent in a dumpster.
A nice upgrade to these, are 1990 Town Car tubular manifolds, commonly referred to as "Lincoln Logs".
These weigh significantly less then the cast iron manifolds, and also flow a touch better. They are also a 100% direct bolt on to your factory down pipes and require no modifications.
They also have another significant plus, and that is they can be used on GT40P cylinder heads. There is just enough room for the plug wires, but if you need to/want to retain your factory exhaust, these are your only options.
GT40P's with Lincoln Logs mocked up:
Next up is Mustang headers. These will not bolt to your factory down pipes. The collectors on the factory downpipes are too small, and just barley make contact with the headers, the angles aren't quite right, and the bolt holes do not line up. A few have "made it work", but in the end were unhappy. What else needs to be done to make Mustang headers work? We'll get to that in a second. Let's look at header options quick.
First up is factory Fox Body headers.
These work great for a modded lopo, or stock HO. You can often find these for very cheap/free, as Mustang guys upgrade to aftermarket. The only mods need for them to work (besides for the rest of the exhaust), is spacers for the brackets for the air box, dip stick tube, and possibly the smog stuff. Those same rules apply to nearly every aftermarket Mustang shorty header.
If your running GT40P's, you will need a "P" specific header, such as these FRPP ones.
Now, in order to run Mustang headers on your box, you will either have to have custom down pipes made, or run a Mustang H-pipe. Factory or aftermarket H-pipes follow the same rules pretty much. Nether fit that great, but can be made to work. A factory catted Mustang H-pipe will not work on a 90/91 as the one cat completely jams against the shift cable. It may work with some mods. You will also need either long wire 02 sensors, or extend the wires on your sensors. Mustangs have the 02 sensors in the H-pipe, as compared to the manifolds on boxes.
Here's a factory Box exhaust system compared to a factory Mustang system.
And an aftermarket Summit catless 2.5" H-pipe
************
This section I need your guys help on, I know some people run mustang extension pipes with pipe welded on, and others run s-10 midpipes. I don't know enough about either to comment on.
*************
As I mentioned, the Mustang H-pipe doesn't fit perfectly. I personally cut the ball flanges off the H-pipe. Make a notch on the pass side pipe which sits at a weird angle, and bend it straight and weld it up. Then I weld some straight pipe back to the mufflers. I have done this successfully on 2 cars now, and it tucks the exhaust up to almost factory levels.
Once you get to the mufflers, you can either dump the exhaust at the axle, or the most popular option is to add 2.5" Impala SS tailpipes. These are mandrel bent, and flow really, really good. As of now, the only place that still sells them is RockAuto. DynoMax 50417 and 50416 are the ones you want.
They require a little love to fit, but are the best pre-bent buy-able pieces. You will have to add extensions too them though.
As you can see, there isn't really a great option for us Box owners as far as aftermarket parts are concerned. Mustang parts work to an extent, as as of now are the best viable option IMO.
Some additional info,
Stock Explorer Manifolds:
Comparison pic:
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