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DIY Explorer 302 Headers

97Sandbox

Elite Explorer
Joined
February 7, 2019
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City, State
Seward, NE
Year, Model & Trim Level
2000 Explorer Sport
As you all likely know, the TMH lead time has gotten absurdly long and OBX headers only pop up once and a while. Since these headers are the only off-the-shelf options for replacing stock cast manifolds, I can certainly see where they have their place.

However, I've been wondering lately how bad it would be to make DIY headers with an online kit. There's a lot of SBF header kits out there, most with either 1 5/8" primaries to 3" collectors or 1 3/4"primaries to 3 1/2" collectors. The kits are pretty reasonable compared to TMH and OBX, coming in at $150-250 for collectors, bent tubing, and flanges (even gaskets and hardware in some kits).

So why aren't more people making their own headers? Do the normal "SBF" header flanges not work with GT40P heads? What can be done to make a new EGR tube to work with custom headers?
 



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To make such headers will require the normal head flanges, the primary pipes in various tight mandrel bends, a tight merge section with very short collector, choice of collector joint, a very good welder/expertise, and imagination with patience. You can't slap together some pre-made header that is cut up to fit.

It will have to be made from scratch, the front two left pipes will have to go outside the steering shaft, and the rest will need to be slowly worked out. The EGR pipe will be a fairly easy step versus the headers, you can weld an EGR bung in the needed place with a pipe that goes to one right primary. The EGR is a low exhaust flow system, any path that includes the same stock EGR pipe features will work. So just use the most common EGR pipe that connects to the intake elbow connection, and make the other end work.

The stock manifolds were made to tuck close to the engine for original manufacturing ease, on the line. TM headers were made to attempt(poorly) to create equal primary pipes, thus they use up all available space and are horrible to install or remove etc.

Just make a shorty header that fits as easily into the space as possible. Leave plenty of room from the steering shaft, the valve covers and heads, the shift cable, fuel lines, AC box etc. Work them out to fit well around the steering shaft, make the collectors at least a true 2.25"(2.5" would be a huge improvement), and ease of R&R labor is what matters. You can place the primary pipes at angles coming from the flange which allow "P" plug wires or normal angle plug wires. Leave plenty of room around the flanges for the bolts and needed sockets or wrenches.
 






Thanks for all of that. If I understand correctly, you're saying normal header flanges will work, it's just that headers for P heads need to leave clearance for the different angle of spark plugs? I thought I'd read somewhere that P heads also had the bolt holes in a different location relative to the exhaust port openings (can't remember higher/lower), but maybe I misread or the person who said it was wrong.

I don't expect there's any way to make a perfect header that leaves good clearance to everything, but it'd be interesting to lay out some configurations different from TMX/OBX and see if making a different set of tradeoffs would come with more pros than cons.
 






It can certainly be done. I have a really nice TIG setup and I’m not bad with it…I’ve considered it.

But to have the room for work, I’m gonna have to take damn near half the front end apart to get in there. Then I need the mandrel bent parts as mentioned…lots of measuring, fitting, trial and error. Tacking, pulling it out, welding…and it needs to be able to be installed/removed when it’s done (obviously).

And on top of it all…is your design going to flow properly? As you know, runner length is important for pulse synchronization, all that fancy nerdery.

Now will just about anything be better than stock? Sure. But if you’re gonna do alllllll that work, you’re gonna want to do it right. Stainless (and time) ain’t cheap!

I’ll be honest, I probably wouldn’t attempt it unless I installed a hot motor.

I do love seeing handmade intake and exhaust manifolds though. Things of beauty.
 






I’ll be honest, I probably wouldn’t attempt it unless I installed a hot motor.
Precisely. This isn't something I plan to do on my Mounty, but I'd be interested when I eventually tear the Mounty apart to yank the 5.0 , spice it up, and drop into my Sport.

I'm currently working at a shop that does a lot of motorsport exhaust manufacturing, so there's plenty of scrap 1 3/4" - 2" mandrel-bent headpipe at my disposal. With header flanges costing less than $50 and collectors around $30 each, it's getting tempting to more seriously consider experimenting with making some headers...
 






Precisely. This isn't something I plan to do on my Mounty, but I'd be interested when I eventually tear the Mounty apart to yank the 5.0 , spice it up, and drop into my Sport.

I'm currently working at a shop that does a lot of motorsport exhaust manufacturing, so there's plenty of scrap 1 3/4" - 2" mandrel-bent headpipe at my disposal. With header flanges costing less than $50 and collectors around $30 each, it's getting tempting to more seriously consider experimenting with making some headers...
There's enough demand here, that a good working prototype could be sent off to the land of reverse engineering to have a large quantity sent back.
 






The last important thing to consider is if they will be removable once tacked up. Gotta be bolt on

Edit. Already mentioned.
 






Sounds like I need to start squirreling away as much bent 1 3/4" headpipe as I can find and plot out potential routes in my head as I refresh the 5.0 in my Mounty!
 






Start w pvc a lot of custom headers are
Mocked up using plastic pipe first cheap and easy to work with
 






Can anyone confirm the diameter of the ball flange for the Explorer exhaust manifolds? I'm considering grabbing a cheap set of used 5.0 Mustang headers to chop up and experiment with, but I think the Mustang flanges are 2-1/4" and the Explorer's might be 2-1/2". I haven't found anything conclusive though.
 






They are 2 1/4", any ball type will mate there fine.
 






Ordered a set of used fox body headers yesterday! I'll be excited to get them in and start dissecting.

After talking with a coworker who does a lot of fab work and especially TIG welding, my plan is to cut up the used headers as necessary (likely rerouting the back three primaries on the driver's side and back two on the passenger side), then play around with primary routing tacking together sections of pre-bent 1-5/8" tubing (I'm lucky the Speedway Motors HQ is less than 10 min from where I work), and finally cut apart my mockup primaries so each can be fully TIG welded then welded to the head flange and collector.

I've been studying pictures of past TMH designs, OBX headers, and even Ford Motorsport headers. I've also been staring at my engine bay a lot haha. I honestly think Bob's passenger side header uses the space quite well, I'd just like to see how much more length I can add to the cylinder 2 primary before it starts to block its own spark plug. On the driver's side I'd like to try bringing the 6 and 7 primaries outside the steering shaft so I can loop the cylinder 8 primary up then behind the steering shaft. With all of this, I think there may be a way to get the primary lengths much closer to equal without sacrificing too much space.
 






Good luck! I love speedway! Their prices and service are right there with summit and jegs. Speedway diy exhaust kits kick ass
 






Good luck! I love speedway! Their prices and service are right there with summit and jegs. Speedway diy exhaust kits kick ass
Glad to hear! My wrenching coworkers all rave about Speedway -- I'm exited to be able to pickup locally too.

I'm planning to get one of their 1-5/8" assortments and a few U/J bend sections. I was initially thinking of going completely DIY with their 1-5/8" SBF header kit (only $149!) and supplementing extra bent tubing as necessary, but realized I'd have to redo the whole exhaust to make use of the 3" collectors...that's a rabbit hole I'm not ready to go down right now. You can buy 2.25" flanges that work with our stock downpipes/cats, but they're so pricy it made sense to just get used Mustang headers and cut them up.

If making a modified 1-5/8" header set goes well, my hope is to use them as a guide to make a 1-3/4" set from scratch in the future when I'm ready for 3" collectors and full DIY exhaust.
 






I would not mess with the primary lengths, to make them more equal etc. That is exactly why the TM headers are terrible to install. All "equal length" headers do the same thing, they snake around on purpose to make the pipes closer in length. All that does is use up the available space, and thus make it hell to install them, plus accessing the plugs, and making the plug wires closer, and burn more.

Instead, do what the OEM do when they make shorty headers, route the pipes the best way to clear the plugs and wires very well, and to allow the whole thing to install easily. The primary pipe length is almost immeasurable as an effect on power or torque. You cannot feel it, and only on a dyno can it be seen as a difference, to the tune of a few horsepower at most. The fuel economy won''t be changed enough to be able to measure it in any way people check their mileage.

I plan to do 1 5/8" headers too, but I'll route the pipes as much away from the steering shaft and plug wires, as possible. I'll move the collector down a bit to wherever there is the most room for 2.5" collectors. I'll be building my exhaust from the back to the front, so at the headers the collectors will be placed where I want them, not where OEM put them for efficient manufacture of the vehicle. That helps the primaries a little, more space for more collector merge volume is good power. The stock collectors are puny, almost nothing, the pipes jamb together right at the ball collector joint. I plan to buy the merge collectors separately and build out from those, keeping as much of the merge length as possible.

Think about it more before you go about making headers that may be as bad to install as the TM's, and still have wires too close to the pipes.
 






And it does absolutely no good to try and make equal
Length headers and then leave one cylinder only 5” long on both heads… silly
Much room for improvement here

Holley/ hooker makes some nice simple headers these days, they hug the block and flow well, very simple design one big tube really, search hooker
Black heart ls swap headers


I posted some pics of the obx headers installed in my engine bay, pics from around the front of the engine not a shot you normally see, maybe helpful here
hok-bhs558_km_xl.jpg
 






I plan to do 1 5/8" headers too, but I'll route the pipes as much away from the steering shaft and plug wires, as possible. I'll move the collector down a bit to wherever there is the most room for 2.5" collectors. I'll be building my exhaust from the back to the front, so at the headers the collectors will be placed where I want them, not where OEM put them for efficient manufacture of the vehicle. That helps the primaries a little, more space for more collector merge volume is good power. The stock collectors are puny, almost nothing, the pipes jamb together right at the ball collector joint. I plan to buy the merge collectors separately and build out from those, keeping as much of the merge length as possible.
My Intent for now is to make headers that work with the rest of the factory exhaust, so the collectors will be similar to TMH out of necessity. If you're moving collectors downstream, there would certainly be more options for routing primaries and increasing collector volume, but otherwise the available space is very limited. In the future when I'm putting a more "built" small block into my Sport -- and likely a full custom exhaust -- I'd envision doing something similar to what you're describing.

I have little doubt my headers will be at least as bad as TMH to install (probably worse on driver's side) and I 100% plan to run plug wire boots. You have to make tradeoffs somewhere; if you're not making any performance tradeoffs, your big tradeoff is probably cost (and there's nothing wrong with that if you have the funds!). Again, the more I study the available space, the more the TMH design makes sense to me -- I'm not saying a better shorty header can't be made, but it'd take someone with more expertise than me to visualize and build it.

Holley/ hooker makes some nice simple headers these days, they hug the block and flow well, very simple design one big tube really, search hooker
Black heart ls swap headers
I did a fair amount of research on "log headers" and my conclusion was that they likely would not hold up well if a custom set were welded together due to the way they develop hot spots which often cause welds to crack (residual stress from weld + uneven thermal expansion = cracks).

"Lake style" headers (cone shape instead of log) are an alternative which help with flow to reduce the hot spots, but good luck fitting those. I can see where a cast log header might be able to survive without cracking -- I wish someone made them for our application!

Sadly I own neither a foundry nor an annealing furnace, so I'm backing away from this path.

I posted some pics of the obx headers installed in my engine bay, pics from around the front of the engine not a shot you normally see, maybe helpful here
Yes, I've been referencing those quite a bit as well as similar shots of headers on installed engines (some good ones on Ranger-Forums). Thanks!
 






And it does absolutely no good to try and make equal
Length headers and then leave one cylinder only 5” long on both heads… silly
Much room for improvement here

Holley/ hooker makes some nice simple headers these days, they hug the block and flow well, very simple design one big tube really, search hooker
Black heart ls swap headers


I posted some pics of the obx headers installed in my engine bay, pics from around the front of the engine not a shot you normally see, maybe helpful here
View attachment 444894
I'd like to find a set of manifolds exactly like this with a T3 flange on it for a turbo.
 






I'd like to find a set of manifolds exactly like this with a T3 flange on it for a turbo.
You're really going to need to find some space for that! Time to go full chromoly tube front end with tubs like the drifters do. They have a lot more space in the bay to begin with since they usually use inline sixes though.
 



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Forgot to follow up! My used Fox Mustang headers came in a couple weeks ago and I think they'll be very useful. They're in much better shape than I expected, I'll get a picture or two before I start hacking them up.

I've scoped out the tubing from Speedway I think I'll need and will get that ordered once I'm ready to start cutting and tacking -- I don't want it sitting around rusting while I'm working on other projects.

I hope to start refreshing my 5.0 in the next couple of weeks and that will make room for header mockup as I disassemble various systems for cleaning and new gaskets, hoses, etc.

Any tips for removing rusty manifold bolts/studs? I bought new studs already, but getting the old ones out might be a heck of a job...
1693572241578.png

1693572699100.png
 






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