V8 Exhaust Question

[markinms]

I'm getting ready to install a set L&L headers on my 5.0L BII. Very well made and come with 2.5" collectors. Went to arrange exhaust system install with local muffler shop and the guy I spoke with "strongly" suggested I reduce from 2.5" to 2.25". My goal was to run 2.5" from the collector to a universal cat, to flowmaster muffer, and out to the back of the vehicle.

What do ya'll think? Does it make any sense to go to a smaller pipe?

Thanks for any feedback!

Mark

 

[Curious Hound]

He probably knows more about exhaust than I do. I have read many times in recent years that with exhaust systems, bigger is not always better. Apparently, you need to keep it small enough to maintain good exhaust velocity for scavenging. That's most of what I've learned. A quick Google search brought up this page that applies some science to the issue. I'm sure others will chime in soon with more info and plenty of opinions. According to the article I referenced, I would guess that a stock 302 would be right on the edge between 2 1/4" and 2 1/2"

 

[19Walt93]

I used a 2 1/2" single system on my 13.8 second, 302 Mustang and on my almost stock 351 Ranger with a Jones Max Flow muffler- it's like a Magnaflow for way less money. Dual 2 1/4" would be enough for a 6000-6500 rpm 302, velocity and torque would be higher with dual 2" for a more truck oriented engine.

 

[RonD]

Whats the collector outlet size?

As long as you are equal to or larger then doesn't matter

The size and length of the pipe from each cylinder and the size of the collector pipe decides the RPM band when you get scavenged power from the exhaust manifold/header design

As long as you don't go smaller after the collector it wouldn't matter, unless you are also looking to do "X" or "H" scavenging as well, then you would want to stay with collector size pipe

 

[markinms]

Thanks for the feedback! Collector size is 2.5 inch. I think I'll stick with my plans for a 2.5" exhaust system and override the muffler shop dude.

Also, thanks for tip about the less expensive muffler. I'll look into that.

Mark

 

[ford4wd08]

I would like to see pictures of this B2 5.0 swap.... I don't see many of them on the forum!

 

[markinms]

Here ya go, I kept a complete photo history of every task completed for the swap.

 

[ford4wd08]

Here ya go, I kept a complete photo history of every task completed for the swap.

View attachment 43069

Looks awesome! I might start collecting part for a swap someday. Looks like you kept the AC box as well?

How did the AOD fit? What transfer case? Do you have a build thread?

 

[19Walt93]

If you're talking about a 2 1/2" single system, I agree, a dual 2 1/2 will lower exhaust velocity and may hurt bottom end. It will likely be louder, too, and I'm not sure where you'd put a dual 2 1/2 system under a Bronco II, please don't run it out in front of the rear wheels.
My Ranger didn't have a heater box when I got it so I used a Vintage Air system, you're evap case really crowds things.

 

[85_Ranger4x4]

I just have 2-1/4" duals on mine, I am happy with how it sounds.

 

[Shran]

I have 2.5" single on mine, a Y pipe that goes into a single in/single out Flowmaster. Sounds good.

I suspect that there is a fabrication and/or muffler selection related reason why he said to go with 2.25".... maybe it has to do with where the inlet and outlet are placed on the muffler itself, I wanted a specific center in/center out muffler recently and it was only available in 2.25". I can't imagine that 1/4" makes any difference.

FWIW Roadkill/Engine Masters did a series of videos on exhaust size, X/Y/Y/etc crossovers, headers, and stuff a while back and I was was left with the impression that it doesn't matter as much as you'd think it would in most cases.

 

[markinms]

If you're talking about a 2 1/2" single system, I agree, a dual 2 1/2 will lower exhaust velocity and may hurt bottom end. It will likely be louder, too, and I'm not sure where you'd put a dual 2 1/2 system under a Bronco II, please don't run it out in front of the rear wheels.
My Ranger didn't have a heater box when I got it so I used a Vintage Air system, you're evap case really crowds things.View attachment 43071

Very nice!

 

[markinms]

The AOD fit fine, although a bit snug in there. I used the stock transfer case with an Advance Adapters AOD to BW1350 adapter. I never created a thread while I was doing this.

 

[ford4wd08]

The AOD fit fine, although a bit snug in there. I used the stock transfer case with an Advance Adapters AOD to BW1350 adapter. I never created a thread while I was doing this.

It is never too late. Would love to see a thread!

 

[19Walt93]

The AOD fit fine, although a bit snug in there. I used the stock transfer case with an Advance Adapters AOD to BW1350 adapter. I never created a thread while I was doing this.

I used a C4 because I had one that I had driven and knew it would be an easy rebuild. I've never built anything with an automatic transmission and didn't know if I'd be able to stand it, if I decide to swap in a T5 I should be able to sell the C4 for a small profit.