85 Bronco 300 I6 Exhaust - Ford Bronco Forum
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post #1 of 17 (permalink) Old 05-11-2017, 08:47 PM Thread Starter
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85 Bronco 300 I6 Exhaust

I know this isnt going to apply to most of you, but im sure theres a lone few out there.

1985 Bronco, 300-6 with a 450 cfm 4bbl carb, 270 duration cam and Clifford 3-into-1 long tube headers with 2.5" collectors.

I decided a while back to redo the exhaust on the bronco. It had a decent system, but i wanted to improve on it. I started with some hedman collector x-tensions. After slicing and dicing, i got them joined into a 2.5" into 3" flowmaster scavenger y-collector. Thats where im at now. It will have a magnaflow spun metalli-cat on the end of the "y-pipe". Then a Borla XR-1 oval muffler. I fired it up with just the muffler clamped to the y-pipe and man was it loud. The cat should tone it down a bit

Original plan was to have it dump before the axle, but i might build a tailpipe.

Anyways, heres a couple pics.





This is the catalytic converter
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post #2 of 17 (permalink) Old 05-13-2017, 02:31 PM Thread Starter
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Got some more work done.

Here is the two y-pipes side by side. You can see the crimp bends and crude Y junction. It was also only 2" pipe. I ran 2.5" into the new Y junction.



Here it is with the magnaflow cat welded on. I used the little sections of straight 3" pipe so i could cut the cat out for replacement and not destroy the y-pipe or muffler.



I am going to run a full tailpipe, as the exit of the muffler is right before the rear axle: too far back for a dump imo.
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post #3 of 17 (permalink) Old 05-13-2017, 06:05 PM Thread Starter
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Got the tailpipe welded up. All thats left to do is get a couple lap joint band clamps for the muffler and position a couple hangers.

Heres the tailpipe, all welded up.

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post #4 of 17 (permalink) Old 05-13-2017, 09:26 PM
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Lookin' good! It'll be interesting to see what kind of performance gain you get.
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post #5 of 17 (permalink) Old 05-13-2017, 09:57 PM Thread Starter
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Quote:
Originally Posted by SRWillis View Post
Lookin' good! It'll be interesting to see what kind of performance gain you get.
Unfortunately itll be hard to distinguish, as i also added a bigger carb. Im doing this now to add an O2 sensor to help with tuning using a wideband AF ratio meter
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post #6 of 17 (permalink) Old 05-14-2017, 08:18 PM
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Quote:
Originally Posted by BigBlue 94 View Post
Im doing this now to add an O2 sensor to help with tuning using a wideband AF ratio meter
How 'bout a writeup on that?
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post #7 of 17 (permalink) Old 05-14-2017, 09:40 PM Thread Starter
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Quote:
Originally Posted by SRWillis View Post
How 'bout a writeup on that?
Installing the afr gauge or tuning the carb? I can do one of the gauge install, but im as green as can be at tuning carbs so that wouldnt turn out well haha.

Im actually going to install a full autometer gauge set at some point (ive got all the gauges already). All ultra light series, 3 3/8 tach and gps speedo, and 2 1/16 fuel level, wideband, oil psi, water temp, volts, and both differential temps. But thats a lot to fit on the dash so im still figuring that one out. Itll definitely have a writeup.

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post #8 of 17 (permalink) Old 05-16-2017, 11:53 AM
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Looking good BigBlue!

I have a 2.5" exhaust on mine and totally love it. However, I've never been 100% happy with Walker's Y-Pipe. It's a great piece for a quick install, but it leaves a little to be desired in the Y-pipe area. I'd love to have it redone like yours.

The O2 install is a piece of cake, and really depends on which sensor you go with, as they all have different wiring/boxes, etc.
I went with a PLX for mine and love it. It has a graph over time, which is invaluable for tuning as you can visually see spikes, bogs, etc. instead of just watching numbers quickly change.

If you have any questions on wideband tuning, let me know. I've been at it for about 2 - 3 years now, and have learned a ton. I will say that after getting a wideband O2 sensor for carb tuning, I realized that anything and everything I did before that was a near waste of time.
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post #9 of 17 (permalink) Old 05-16-2017, 12:50 PM Thread Starter
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I didnt go with the walker on my 351 because i didnt like the crimp bends or how the two downpipes merged at a right angle.

Ill keep ya in mind if i have questions with the wideband. I did pick up a set of accelerator pump cams and 35-50 discharge nozzles for my carb. Should all be here tomorrow with the clamps i need to finish this exhaust up.

Overall im very pleased with the fit and how it tucks completely up inside the frame.

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post #10 of 17 (permalink) Old 05-19-2017, 09:30 AM Thread Starter
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Well i got the muffler clamped in. Its a bit snug next to a brace under the rear seat area, but after a little coersion, itll clear just fine. With the cat and tailpipe, its still loud, but not obnoxious. The xr1 muffler has a deep growl at idle, and a roar under throttle. Nothing like the old flowmaster that was on it, it doesnt have that hollow sound. The little cat definitely knocks the fumes down significantly: glad i decided to use one.

Im debating if using vht on the system is worth the time and effort, and im gonna weld in the o2 bung tonight. Then all thats left is a couple hangers to keep it all in place.

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post #11 of 17 (permalink) Old 05-19-2017, 11:08 AM
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I agree, I'm glad I have a cat on mine. I get a little frustrated with people who just want to yank it out because they don't have to pass emissions. They're a good thing to have on there, keep our air clean, gets rid of fumes, etc. I like my fresh air. A good working cat shouldn't have any noticeable affect on your power either.

What is VHT?


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post #12 of 17 (permalink) Old 05-19-2017, 11:57 AM Thread Starter
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VHT flameproof high heat paint.

Ill admit, ive always been one of those who rip the cat off, but with the carb and the ever rising emissions in the air, i decided to man up and do the right thing. Its amazing how well it works, even being only 4" long of actual catalyst.

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post #13 of 17 (permalink) Old 05-19-2017, 12:14 PM Thread Starter
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Forgot to post a pic of the tailpipes next to eachother


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post #14 of 17 (permalink) Old 05-19-2017, 07:58 PM Thread Starter
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Heres the location of the o2 sensor bung.



Here is a full mock-up before i paint it. That will happen tomorrow.



This is the paint ill be using.


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post #15 of 17 (permalink) Old 05-20-2017, 02:53 PM Thread Starter
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Paint time! I started by sanding with 120 grit to give propper adhesion. I followed that with a wipe down with acetone. I came in with a light coat of the VHT primer, followed by a full coverage coat ten minutes later. After 20 minutes i shot it with a light coat of the VHT flat aluminum paint, followed by two full coverage coats, all ten minutes apart.

Pics:
Prepped and ready to paint



First coat of primer



Final primer coat on muffler



Final coat of aluminum paint






Ill install it tomorrow, to give it plenty of time to dry. This VHT product must be ran through a specific heat cycle in order to chemically cure and be gas/oil resistant. It involves a couple idle cycles and a 30 minute easy drive.
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post #16 of 17 (permalink) Old 05-21-2017, 01:34 PM Thread Starter
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Installation complete!

Sorry for the sideways pics, supermotors likes to rotate portrait pics from my phone.









Haha and this one is upside down...
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post #17 of 17 (permalink) Old 05-21-2017, 03:23 PM
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I thought those tires looked really sticky!

Great looking exhaust!


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