exhaust, headers back

[johnbeck]

I have a 302, mild(60's 289highperformance grind)cam, AFR 165 heads, Edelbrock 600cfm carb and performance manifold, installing Hooker mid length headers. The header collector is 2 1/2". I need exhaust from the headers back. A local muffler shop said just run the 2 1/2" all the way out. Is 2 1/2" going to be bulky, is it going to give me significant enough gain in performance to bother with? I'm not building a street racer, just a fun ride to "zip" around town. I don't want noisy exhaust so what should I buy for reasonably good performance without attention getting noise volume? Thanks John B

 

[rguest3]

I prefer a 2-into-1 exhaust coming together on the passenger side before the transmission crossmember. Use 1 Muffler with Dual-Inlet / Single Outlet with the tailpipe out the passenger side rear at the stock location.

2 1/4" pipes from headers to muffler. 2 1/2"-3" single outlet from muffler out the back. A Flowmaster Super 50 series has a nice mild tone and the Gibson Superflow is pretty quiet as well.

 

[WheelHorse]

Technically you would also need to factor in RPM. Seeing how most Bronco owners aren't revving out to 6500 where you'd be using all of the flow of the AFR heads, I'm most positive you would do just fine with a 2.25.

You could go 2.5 into the mufflers down to a 2.25 out the back for increased scavenging.

Or the classic 2.5 into a single 3" would also work for a street Bronco as mentioned by rguest.

 

[DirtDonk]

A local muffler shop said just run the 2 1/2" all the way out. Is 2 1/2" going to be bulky, is it going to give me significant enough gain in performance to bother with?

Is this recommendation based on a full dual-exhaust system all the way back? Or are you planning to cross over for a 2-into-1 setup?
A single 2.5 is a kick-butt system for a mild Bronco engine. Dual 2.5's on the other hand is likely overkill for your stated use and just get in the way of future work underneath the rig. So yes, it's bulky.
Funny how much it feels like that little extra 1/4" of diameter makes a big difference in lost space underneath.

Really though, no matter what size tube you use, a full dual exhaust on a Bronco can be a royal pain, on the driver's side mostly, unless the installer is very, very good.
Which is why most of us have gone back to high performance single exhaust, or a dual but on the passenger side only.

I doubt you'd actually feel any loss in lowest rpm performance (if there is any actual difference) under normal use between running dual 2.25" vs dual 2.5" tubing.
Dual 2.25" tubing has slightly more flow volume than a single 3" tube does. And a single-3 can still support a ton of power! Member MtFit's red Bronco buggy had a single-3" through a flowmaster and shorty headers and could literally roast the 38" Swampers in a mild throttle roll-on. Get the rig rolling about 10mph, push the throttle down and watch the smoke coming off those big tires.
Just to give you an idea of what kind of power a single exhaust can support if it's done well. The 419ci engine dyno'd at way north of 400hp and could rev to the moon. Or to the rev-limiter, whichever came first.;D

Remember too, in any scenario it can all still come down to choosing the right muffler(s). There are compromises to be made between sound (tone), sound (volume), and flow characteristics. Tubing aside, the muffler can make or break the performance of your system.
Or it can make or break your happiness, based on getting the sound just right.

All in all, you don't need the big tubing. It's nice to get it right the first time, it's just not always easy. But uh, no pressure or anything like that!%)

Paul

 

[xltboy]

I ran 2.5 all the way back with dump behind the wheels. I also have shorty headers. No issues servicing anything, I had to remove the 4r70w with the d20 attached and it all dropped out without touching the exhaust. Driver side is routed high enough so you can get the drain plug out of the D20. The key is to have someone competent bend the exhaust so it clears everything. The overall noise level is more dependent on the type of muffler chosen in my opinion.
Xltboy

 

[pcf_mark]

My $.02.

I have dual exhaust out under the bumper. That stunk up the cab and the guys on here straightened me right out.

Then I moved the outlets to the left and right behind each tire. No crossover pipe just duals. Sounded freaking amazing. Using Dynomax/Summit 2 1/2 in out mufflers cost about $30 a side.

Then I did other stuff and put the exhaust all down one side. Had the same power that I could tell but sounded way less fun. Same muffler just one of them.

Then I put on duals using muffler from a newer Mustang or Camaro I got for free. These sounds like total crap.

Pipe diameter really does not matter once you get past 18" or so after the collector. The restriction of the muffler determines your loss.

I would find a sound you like them build around that. I am now going to Magnaflow 3" in 2 x 2 1/2 out this time around. There site has a great was to listen to the mufflers.

 

[johnbeck]

I really value your opinions. My situation changed dramatically when I found the stock exhaust manifolds were resting on the side of the AFR heads. I could possibly grind the exhaust manifolds to clear but I'll tired of altering things. I 'm going to install the Hooker headers. Would have been happy with stock exhaust manifolds but wasted time hunted for quality new or good used only to find the fitment issue. With my build it sounds like 2 1/4" to the muffler or mufflers will breath enough for my needs. I don't know the rpm's but I just wants performance that pulls when you start, not kicking but laying fairly heavy on the throttle. I'm having a talented exhaust guy do the installing. Coming off the headers is it easier to run duals straight back to dump behind the the rear tires, or run 2 into 1 ? I know the duals should have an H pipe- that crowds the under side some. Last is mufflers. I'd like great sound but not attention grabbing noise. Thanks All for your help! I'm almost there, back on the road. John B

 

[ManTruck]

Do yourself a favor and get the shortie headers if you are considering future work as well. I went that way recently after the new set of long tubes which replaced my old 30 year old long tubes. Once i decided to long arms and an atlas I went to 2 into 1 and wish I would of done that in my original replacement of the long tubes. Just my experience is my reasoning for this suggestion.

 

[pcf_mark]

2 into 1 helps get around the transfer case. I never go offroad but my duals looked a little funny you could see the one pipe taking a goose neck around the t-case drop. If you cross over under the transmission you can pack it up in there really right. I like long tubes you actually gain low end torque in my experience.