DIY Explorer 302 Headers

[Josh P]

Interesting. My M5R1/3.73 drivetrain has my Sport right around 3k RPM at cruising speed. That'd jump another ~300 RPM with 4.10s. Fifth gear is about the same ratio for an M5R2 and I don't expect a 302 to be more rev-happy than a 4.0. I guess 3300 RPM isn't terrible, just drains the fuel tank quicker.

What size tires and what speed on the highway?

 

[97Sandbox]

Stock height 29" tires, speed limit 75 so I usually set cruise at 82.

 

[CDW6212R]

What size tires and what speed on the highway?

Tires about 29", 70mph at maybe 1800rpm, that's about what I expect with 3.08 gears and the same high gear of .70:1 like any OD trans. That's my dream cruising down the highway, if it makes enough torque to do it.

 

[97Sandbox]

After realizing how much better I got building the passenger side header, I decided to go back to #5 which had been bothering me. I got it a little lower and much closer to the block. I'll probably still do a little denting around the 5 and 7 plugs, but much less now.

 

[vroomzoomboom]

i would like to think i have built some stuff from scratch and dont really consider myself a fabricator as well, but thats why more and better then i could ever do! nice job!

 

[410Fortune]

Yes our sport trax is at 2900 rpm at 70 mph I have been considering 3.73 to help with tbis
Slightly, mostly because I have the axles and I have a 96 front diff with the cad I was thinking of putting on this trax in an effort to get the most mpg possible. But for now I am going to install slightly larger tires I’m running 245 the snow tires are 265 I think 265 will fit it nicely (31” basically) and will drop the rpm slightly at 70-75 mph

She has plenty of torque so it is a non issue at lower speeds, the first gear is barely usable for in town driving

Keep up the good work

 

[97Sandbox]

i would like to think i have built some stuff from scratch and dont really consider myself a fabricator as well, but thats why more and better then i could ever do! nice job!

I don't think you're giving yourself enough credit! I haven't read the full Evil thread, but I've seen you do plenty that looks harder than this.

This job is tedious, but with the flanges, bent tubing, and a welder, anyone can do it. Patience and willingness to undo/redo work have been the most important parts. Otherwise, all I'm really doing is cutting tubing with an angle grinder/portaband and burning it together with the MIG gun.

We need more folks tackling this job, there's so much to learn from taking different approaches! There's a lot that TMH does well given the constraints, but clearly there are other options for primary routing which have different pros and cons. In the future, I definitely want to look into redoing the rest of the exhaust system which will open up opportunities for moving collectors, switching to V band connections, etc.

Once I get these headers completely finished, I'll have to make a condensed how-to with the techniques I've been using -- I assure you, there's not that much to it!

 

[97Sandbox]

I was cruising right along stich welding until I ran out of wire...dang it!

Decided to work on a couple other areas I've been putting off.

First, shaping the inlets to close gaps before welding

I used a hammer and punch to push the tubing against the inside of the flange.

Then I practiced grinding back some weld where I'll want to gasket match

Carbide burr works well, but the fine shavings of weld are sharp! Need to wear gloves next time.

Test fit again to make sure nothing warped...all good

And starting preparing for EGR bung placement

Slow and steady. I'll get the 5 pound roll of wire this time.

 

[CDW6212R]

Very good. Those exhaust flanges look very thick and sturdy, what thickness is that and were there other choices?

 

[97Sandbox]

The header flanges are Speedway's Small Block Ford 289-351W Header Flange - 1-5/8 Inch, which their site lists as .31" so ~5/16". In actuality, I measured my flanges and they're more like 3/8".

There's lots of SBF header flange options out there, but I liked these due to their flat oval design which makes it easy to just form the primary inlet tubing with a vise/hammer and insert them into the flange. A lot of SBF header flanges have rectangular openings which is more like the exhaust port in the head, but it would be much more difficult to form circular tubing into a rectangle.

 

[97Sandbox]

I've been thinking about the next bottlenecks in my exhaust system now that I'll be getting away from the stock manifolds. What's all of your experience with the rest of the exhaust?

As I understand, the 5.0 has two 2.5" downpipes each with two cats that go into a dual-in/single-out muffler. But the muffler outlet and tailpipe are only 2.25"? Seems odd to me. I'd think dual 2.5" tailpipes or a single 3" would be more appropriate flow-wise. Mufflers for both configurations appear to be readily available, granted it would be hard to route either tailpipe setup along the stock path...time for side exit? Now that I'm getting familiar with cutting, routing, and welding tubing, a DIY exhaust sounds pretty manageable.

I'm not going to delete all my cats -- if anything, I'd delete the secondaries and consider replacing the primaries with newer high-flow cats. But it seems to me that the muffler may be the primary bottleneck before the cats.

 

[CDW6212R]

You have a good handle on the exhaust fabricating now, obviously. The back end is bad because it's half the flow of the front, being just one single path the same size as the front section. Installing a 2nd muffler doubles the airflow of the back section.

The stock cats are 2.25" pipes, just like virtually all V8 Fords have had since the early 80's(single by routing one bank straight into the other).

The front pipes are restrictive because of the four restrictive cats. Do remove the rear two and use some better flowing front cats. Making them 2.5" would help but it's not a huge deal if the engine will be just a mild 302. All of the narrow connections are bad for flow, the 2.25" ball connectors neck down to maybe 2", measure the stock collector outlet size. That's where it would help to use a different connection, the old style flat four bolt flange, or much better the V-band flanges.

 

[410Fortune]

Secondary cats go bye bye
They are worth $50-150 each btw depending on the platinum and palladium markets

flowmaster makes some nice cheapish 2.5 compact cats to replace your primaries Dual all the way out is the way to go, however I do setup Many trucks with a dual inlet single outlet muffler, usually a 3” tailpipe, less plumbing and only one pipe going over the rear axle and out the truck… cheaper and way easier, still sounds good and makes good power for a stockish 302

Now that I have done a couple of rigs with true duals and a crossover… we’ll all my
Personal 5.0s will be setup with some rendition of true duals…. It just sounds proper for the pushrod sbf

 

[CDW6212R]

That too, bank something for the old cats, and duals do sound much better.

 

[97Sandbox]

All of the narrow connections are bad for flow, the 2.25" ball connectors neck down to maybe 2", measure the stock collector outlet size. That's where it would help to use a different connection, the old style flat four bolt flange, or much better the V-band flanges.

My header ball flange IDs are around 2-1/8", better than the cast manifolds I think, but definitely not great. If I fab downpipes in the future, I'm definitely taking the opportunity to cut off the ball flanges and swap for v-bands if I can find a way to get access to one on the driver's side.

flowmaster makes some nice cheapish 2.5 compact cats to replace your primaries Dual all the way out is the way to go, however I do setup Many trucks with a dual inlet single outlet muffler, usually a 3” tailpipe, less plumbing and only one pipe going over the rear axle and out the truck… cheaper and way easier, still sounds good and makes good power for a stockish 302

Got a part number for the flowmaster cats?

Do you think a 3" tailpipe would work on a stock height Ex? I assume it works on a lifted one, but even 2.5" was tight between the right rear shock and frame on my '97.

Now that I have done a couple of rigs with true duals and a crossover… we’ll all my
Personal 5.0s will be setup with some rendition of true duals…. It just sounds proper for the pushrod sbf

What type of crossover do you prefer and where do you like to put it? Have you run duals all the way out the back, or mostly side exit on Rangers and 'tracs?

 

[410Fortune]

Side exit near impossible without body lift
No way to go over the frame

I have never installed a 3” pipe on a non lifted explorer but I am sure there are paths to take a 3” pipe
Spintech also has oval tube available

Flowmaster cats I just search summit 2.5”
Cat

 

[97Sandbox]

Side exit near impossible without body lift
No way to go over the frame

I was thinking under the frame, ahead of the rear right wheel, but that'd probably end up hanging too low for comfort.

I have never installed a 3” pipe on a non lifted explorer but I am sure there are paths to take a 3” pipe
Spintech also has oval tube available

Sounds good. I bet I could just oval or dent the tube around the shock and it'd be fine.

 

[97Sandbox]

EGR bung notched and welded

Exit flange nuts welded too

All my primaries are welded now, so next up is to pull the collectors off and start making merge spikes and finish welding what will be inside the collectors.

 

[Blown]

2-1/2" down-pipes for the win! That is the best size behind your headers to get some scavenging and thus better performance. What kind of power are you building? Cutting and pasting what I found below.

350HP Header Calcs with the stock, very mild, cam:

Primary Tube Length is 44.64, Diameter is 1.41 inches, & Collector Diameters are 2.44 inches

My assessment: The TMH primaries are short, The stock Collectors/downs are small at 2.25 for scavenging but both are large enough for CFM/flow. 350HPX2.2CFM/HP = 770CFM 2.25" flows 810CFM for Duals up too 369HP.

Dual 2-1/2" flows 1014CFM max. or 461HP

Single 3.00" 744CFM or 338HP

 

[97Sandbox]

Right now I'm not really "building" this 302. I just gasket matched the lower intake and cleaned up the casting lines in the upper and EGR/intake elbow. Eventually the engine will come out of the Mountaineer and go into my Sport at which point it will likely get heads and a cam, possibly the stroker treatment if funding allows. 400+ hp would be the goal at that point. But for now, I'm just making the most of what I can with the engine in the vehicle and it partially coming apart for new gaskets.

My cast manifolds were pretty rusty on some sealing surfaces and the bolts all needed to be ground/drilled out, so I just decided to try to make headers. It's something I've always been interested in exploring given the lack of readily available headers.