DIY Explorer 302 Headers

[410Fortune]

We are happy you did! Great work!

 

[Blown]

You can build man, no hurry for larger downpipes till you are making more power. The cats are restrictive though, especially 4 cats! 2 1/2" duals will handle 400HP very well 2-1/4" and a single 3" come-up short.

I may very well stick around the 370HP mine is making now. That maxes-out the stock 2-1/4" stock downs. I had heard of gutting cats but that makes a large cavern/expansion area which may effect flow. It appeared I could run a 4 1/8" hole saw through the secondary cats which would increase flow dramatically along with the still existing flow through the cat honeycomb. This can be done easily without completely gutting the cats or even having to remove them. A guy I know did that and got great results here in Colorado. CO is a CARB state, but he is out of the sniff-testing counties. They do not allow non CARB parts from the cats forward in CO. and it looked stock.

 

[97Sandbox]

Thanks!

Yes, after research and conversation on here, it seems remaking the downpipes with 2.5" tubing, v bands instead of ball flanges, and just two newer cats will be well worth the effort.

Still on the fence about running an x pipe to dual 2.5 or just a dual inlet single outlet setup. Maybe a 3.5" tailpipe would be better suited? That seems huge, but that's what a lot of powerful trucks have from the factory now and I assume the engineers have their reasons.

I probably won't dive into the rest of the exhaust for a while though. Like you said, stock engine probably doesn't need it. Plus I've got other fun plans for my Mounty.

 

[97Sandbox]

The moment you've all been waiting for without realizing you were waiting for: direct comparison to TMH!

I sourced a set of used, damaged headers from a fellow forum member for the sake of furthering my DIY header deep dive. I'll try to get more pics in the engine bay if it stops snowing anytime soon.

TMH driver's side is tall! I'm sure this makes for better steering shaft clearance, but at the expense of the #7 primary running closer to the fuel line. TMH is probably better for valve cover pulling, but the header itself will be harder to snake in place.

Passenger side we have two fairly different ways to accomplish the same thing. My #4 runs under the heater box, TMH runs alongside it. That's of course why TMH needs custom EGR tube and I don't.

General impressions:

• TMH are very well made. TIG welds in primary sections look great (unlike my bulky MIG stitches), primaries are made from custom bends that fit together nicely, and all the flanges look like great quality.
• The same challenges created by using stock downpipes are evident in both my headers and TMH. This seems obvious when I say it, but hits home when you consider the challenges I faced getting the collector locations and orientations just right. You'll note in the pictures they're almost exactly the same between TMH and mine, I believe this happened because it is a necessity.
• Both sets neck down to about 2-1/8" ID at the ball flanges -- this is of course the same ID as 1/16" wall 2-1/4" OD tubing like the downpipes, so you're not really losing anything. However, since my collectors go into 2-1/2" tubing, I can cut off the ball flanges and run 2-1/2" V bands in the future with custom downpipes. TMH can't do that, their collectors neck down to 2-1/4".
• Everything looks better with the smaller 1-1/2" primary tubing: tighter bends, more space for hardware, and I'm sure better clearance in the vehicle. Clearly sacrifices have to be made to run larger tubing, but I'm going to keep pushing and prove it can be done (even if it won't be worth it until I redo the rest of the exhaust).

Stay tuned!

 

[410Fortune]

What the

Where did you get those? Do you get to keep them? Are they for sale! Will you repair them? Why did we now know about this earlier!?!? What a score!!

I like yours better lol

Those are some early tmh just fyi he changed them a bit over the years

 

[vroomzoomboom]

take note on where some of the shinny spots are for the passengers side. thats where they may have come into contact due to bad motor mounts, or major engine torque.

 

[Turdle]

take note on where some of the shinny spots are for the passengers side. thats where they may have come into contact due to bad motor mounts, or major engine torque.

So it was you. Good man, as always.

 

[410Fortune]

“May have” hahahahahahahaha “major engine torque” I love it you had me laughing this am

 

[vroomzoomboom]

So it was you. Good man, as always.

“May have” hahahahahahahaha “major engine torque” I love it you had me laughing this am

ya know, im not saying i know where he got them from, but im sure the guy that sold them to is a pretty cool cat. or at the moment a cold cat...

 

[97Sandbox]

Haha I can leave my source a mystery, but sounds like we already know. I will be keeping the TMHs and will likely repair them, but for now just using them for reference. It's very helpful to have a set on hand, wish I'd had them in the beginning, but then again I probably just would've copied them and we wouldn't have learned as much.

When I was a few days into my DIY build and feeling discouraged, I started a parallel path to find a set of TMH to use for reference (or just run them instead of making DIY -- lame, I know). There were minor delays and in the meantime I made good progress on my custom set. Now I suddenly have two sets of not quite functional headers haha!

I'll be coming up with a leak test to check for any welds I missed before I get my headers coated. I'll test the TMHs too to figure out where they need repair.

 

[Blown]

Great post with the older TMH's! The 5.0 X manifolds are the worst and it looks like you've got them beat!

Good luck with testing and final welding/finish. I look forward to seeing it.

You asked again about 3" pipe. The table I found below is based on 2.2CFM Exhaust per HP. They say that is a high estimate, to perhaps leave some room for restrictions.

The next weakest link in the exhaust is the stock muffler with 2" inlets, but it is still good to something around 289hp.

An inexpensive, dual 2-1/2" inlet 3" exit muffler with turn down or tailpipe is good too 339HP, based on the 3" exit.

The stock 2-1/4" downs are good up to 371HP.

Dual 2-1/2" downs and mufflers gets you to 463HP!

Pipe Diameter (inches)​	Pipe Area (in2)​	Total CFM (est.)​	Max HP Per Pipe​	Max HP For A Dual Pipe System​
1 1/2​	1.48​	171​	78​	155​
1 5/8​	1.77​	203​	92​	185​
1 3/4​	2.07​	239​	108​	217​
2​	2.76​	318​	144​	289​
2 1/4​	3.55​	408​	185​	371​
2 1/2​	4.43​	509​	232​	463​
2 3/4​	5.41​	622​	283​	566​
3​	6.49​	747​	339​	679​
3 1/4​	7.67​	882​	401​	802​
3 1/2​	8.95​	1029​	468​	935​

 

[97Sandbox]

Finally had an opportunity to get out in daylight and play around with the headers and do more comparisons.

With the heater box out, passenger side TMH installs with minimal issues.

Clearance is pretty good all around and spark plug access is fine. With the heater box in, the #4 primary is right along the side of the heat shield.

With my passenger header, it's generally a similar story, just tighter everywhere due to the larger tubing.

My cylinder #4 primary touches the underside of the heater box heat shield. This was the plan.

One thing I decided after this trial fit is that I want to cut off the locking nuts I welded on the exit flange and replace them with normal nuts. It seemed like a good idea, but it's hard enough to get access to the inner bolt, I don't want them to be harder to turn than they need to be.

 

[97Sandbox]

Driver's side it gets more interesting.

As I showed before, TMH driver's header is really tall, that makes it very tough to sneak into place. I mean really tough. And that stupid flange for the two-piece #5 primary gets caught on everything.

I do really like how the #6 and #7 primaries are spaced so the steering shaft bolt passes between them, it's a clever way to avoid a clearance issue.

Valve cover clearance is good.

My header is a lot easier to sneak in, but comes much closer to the valve cover. I also elected to do some denting to clear the steering shaft bolt better.

I'm going to have to get creative with the dip stick, but I'm not too worried about a little bending and a custom bracket. This seems like a better route than trying to follow the stock path.

All in all, I see pros and cons to both designs and I'm sure there's a more optimized design somewhere in between. I'm going to go ahead and finish what I've started, but I definitely think a Rev 2 driver's header will be warranted in the future. Hopefully I can TIG by then.

 

[Blown]

Great job! you jumped-in acknowledging a lack of experience and did it! I wouldn't have tried. I may now after your example but probably wont realizing how much time and effort you have put in. I think I will work on better downpipes.

 

[vroomzoomboom]

Finally had an opportunity to get out in daylight and play around with the headers and do more comparisons.

With the heater box out, passenger side TMH installs with minimal issues.
View attachment 447744
View attachment 447745
View attachment 447746
View attachment 447747View attachment 447748
View attachment 447749
Clearance is pretty good all around and spark plug access is fine. With the heater box in, the #4 primary is right along the side of the heat shield.
View attachment 447750
View attachment 447751

With my passenger header, it's generally a similar story, just tighter everywhere due to the larger tubing.
View attachment 447752
View attachment 447753
View attachment 447754
View attachment 447755
My cylinder #4 primary touches the underside of the heater box heat shield. This was the plan.
View attachment 447756
One thing I decided after this trial fit is that I want to cut off the locking nuts I welded on the exit flange and replace them with normal nuts. It seemed like a good idea, but it's hard enough to get access to the inner bolt, I don't want them to be harder to turn than they need to be.

thats exactly how i took that one out. never done it that way, and figured i would try it. couldnt believe how easy it was. also, does your header that you have made come close to the plastics splash shield? you might also want to get as much room as you can between the heater box, and the header. i melted 2 boxes a few years back while tuning the truck (had the timing waaaaaaay out and the heat the headers pumped out was unreal.)

 

[410Fortune]

With the heater box lid off you can simply heat it with a heat gun and re shape it to clear your header
Or hack that part of the box out and replace it with tin/rivets/ fiberglass

You will want some serious heat shielding there either way so your cold air stays cool in summer. Maybe even wrap the header tube where it comes close? A simple tin heat guard with some air gaps can also work wonders.

I have v8 stuffed into bronco ii with a small body drop… I know all about how much heat headers can put off, enough to melt your shoes on the passenger side before I did a bunch of heat shielding inside and out

 

[97Sandbox]

Great job! you jumped-in acknowledging a lack of experience and did it! I wouldn't have tried. I may now after your example but probably wont realizing how much time and effort you have put in. I think I will work on better downpipes.

Thanks! It's definitely a lot of time and effort, but if you want headers and don't want to wait for TMH, it's what must be done. I know I've said it already, but when you consider the labor that goes into these, TMH look like an absolute bargain.

does your header that you have made come close to the plastics splash shield? you might also want to get as much room as you can between the heater box, and the header. i melted 2 boxes a few years back while tuning the truck (had the timing waaaaaaay out and the heat the headers pumped out was unreal.)

It will come somewhat close but not touch the splash shield. Thankfully the primary sits lower than the plastic part, and the fiber part of the shield bows out in that area for the shock tower.

I didn't want to take the #4 primary any lower because it would start getting close to the shock tower unless I put another jog in it, which would make plug access worse. This job is all about balancing tradeoffs. I do plan to wrap the section of tubing running under the heater box (and a few sections on the driver's side too).

With the heater box lid off you can simply heat it with a heat gun and re shape it to clear your header
Or hack that part of the box out and replace it with tin/rivets/ fiberglass

You will want some serious heat shielding there either way so your cold air stays cool in summer. Maybe even wrap the header tube where it comes close? A simple tin heat guard with some air gaps can also work wonders.

I have v8 stuffed into bronco ii with a small body drop… I know all about how much heat headers can put off, enough to melt your shoes on the passenger side before I did a bunch of heat shielding inside and out

This is all great to know! I'm hoping the ceramic coating, wrap, and retaining factory heat shields will be sufficient for thermal management, but we'll see. Adding something to protect the passenger's foot well (at least more wrap around the collector) is a good idea that I would have missed.

 

[97Sandbox]

"Ported" some of the bulky weld back off:

I'm glad the Remflex gaskets are for taller ports because the Speedway header flange doesn't look like it'd seal the top of the P head exhaust ports with the OEM-style gasket in the picture above.

Started my merge spikes, it's all coming together as planned:

I will weld, hammer, repeat until I work my way to the end of the spike. Then I'm sure I'll do some cleanup grinding. It's going to be tricky stitching along the edge without melting the spikes.

 

[Muleman36]

I'm a pipe welder by trade... If I had a set of TMH on hand, I'd be happy to build headers for the group.

 

[Josh P]

I'm a pipe welder by trade... If I had a set of TMH on hand, I'd be happy to build headers for the group.

The forum member that burned holes in his trying to repair a crack needs to talk to you.