Getting ready to pull the trigger on a new exhaust system

[Johnnyb]

So it's time to pull the trigger on a new exhaust system. One thing I'm certain of is that if I take it in and say "do it" I won't get what I want. I need to provide fairly specific specifications for the shop to build to, but I have a couple of questions for those more experienced. Also I'm thinking about this post from earlier: https://classicbroncos.com/forums/threads/anybody-added-a-cat.327048/page-2

I've decided that I want to use a crossover and have the exhaust exit passenger side rear. I also want to add a CAT, so that will preclude a two into one muffler. Lastly the ProFlo4 only has one exhaust gas oxygen sensor so I want a bung after the crossover joins before the CAT.

• What size tube would I specify from WH shorty headers to crossover?
• What size tube from crossover to muffler? (This will be size of CAT)
• What size tube to exit the vehicle pass rear?

It's a 1995 5.0 block & heads, my goals are a general purpose exhaust system that's not too noisy but also not too restrictive.

THX,
JB

 

[.94 OR]

Is there a sweet spot for distance behind the collector for the O2 sensor so it maintains heat?

 

[Bruners4]

'97 Explorer swap with Ford EFI and Scott Drake mid-length headers. I did 2 1/2" from the headers to a Y-pipe on the passenger side into 3" pipe. Straight back w/o a CAT to a flow through oval muffler and a tail pipe exit pointing to the right rear corner of the tub/bumper. Both of my O2 sensors are 4" ~ 6" from the header collectors. Nice deep mellow tone.

 

[.94 OR]

'97 Explorer swap with Ford EFI and Scott Drake mid-length headers. I did 2 1/2" from the headers to a Y-pipe on the passenger side into 3" pipe. Straight back w/o a CAT to a flow through oval muffler and a tail pipe exit pointing to the right rear corner of the tub/bumper. Both of my O2 sensors are 4" ~ 6" from the header collectors. Nice deep mellow tone.

Any issues with the GT40P (assuming) heads and the headers for spark plug access?

 

[Shimmy]

i'd go 2.5" from header to tail. i suppose you could do 2.25" from headers to cat, then something larger to muffler to tail if you want more clearance up front. overall it won't make much of a difference.

 

[Johnnyb]

Any issues with the GT40P (assuming) heads and the headers for spark plug access?

Plugs are PITA, but doable. Mostly the brake booster is in the way.

 

[.94 OR]

Ok, I don't run a factory brake booster, so maybe that would be in my favor.

 

[Soylent]

I bought mine 8-10 years ago but believe it is the Duff 2 in 1 with the magnaflo. I think it is 2.25” from shorties to the muffler then 2.5” after. I had my local shop modify and weld it several times to get around the AX15 and add bungs for upcoming Proflo. I suppose you could put the Y earlier for the cat. Mine comes out behind passenger rear tire.

 

[Bruners4]

No GT40p heads anymore. Swapped them out for some BPE aluminum heads. I had long tube headers until the exhaust shop pointed out that the Atlas was in the way and I refused to have the pipe hanging lower than the transfer case. I still have those TBP coated headers hanging around needing a new home.

 

[Johnnyb]

Thanks for all the pictures and suggestions. Today is the day. I took the EB over to a nice old guy named Manny here in Flagstaff who seem to know what he's talking about. I'm going two to one with a y-pipe and the EGO sensor right behind the y, then a 2.5 inch cat, muffler 2.5 in all the way out the back passenger side, dodging the inboard shock hoop and the 23 gallon tank. He asked me for a couple of days because he didn't want to put anybody else in his shop on it, so apparently he's doing it himself.
I'll share pictures when it's done whether it's a success or a disappointment.

-JB

 

[.94 OR]

And a polished 8" can off the back corner?
Tell me you are going to have the zoomie can...
Anyway, looking forward to pics and a review regardless.