Exhaust time...what you got on yours?

Renodemona · Post by **Renodemona** » Sun Apr 05, 2015 6:55 pm

The 401 Lives! And the exhaust leaks terribly from the manifolds back. Rust, holes, yuck...
Time for new pipes and mufflers. Currently running true dual with what looks like some cheapy small mufflers. What have you guys put on and have you liked it? 2.5" or 3"? I don't really care about the sound per se, just don't want something too loud and annoying when I'm just driving around town. Thanks for any input!

Herk · Post by **Herk** » Sun Apr 05, 2015 9:02 pm

2.25" primaries into a 3" single. Use the biggest muffler you can fit under the rig. Something like a Walker 22636 http://www.summitracing.com/parts/wlk-22636/overview/

And yes, it looks like a school bus muffler, because that's basically what it is.

Post by **Stuka** » Sun Apr 05, 2015 9:18 pm

On my cherokee I had 2.5" from the Y-pipe back with a turbo muffler. Sounded great, not super loud, good tone, no drone.

flawlessfailure · Post by **flawlessfailure** » Sun Apr 05, 2015 10:42 pm

I used a thrush welded muffler, big beefy mufflers full welded truck mufflers (like a flow master knock off) but half the price, it gives it a good throaty v8 sound and not obnoxiously loud, I like it a lot and only $40 at pep boys

Cheap Hobby · Post by **Cheap Hobby** » Mon Apr 06, 2015 12:42 am

If you need a y pipe have it made. The only one available is from Walker and it is thin, crush bent galvanized . If you have made make sure the shop knows we use a flanged donut seal not flat paper gaskets. The paper will be blown before you get home. The Walker muffler above is great and very quite mine has had one for years. Go with single exhaust, duels and stock tanks don't mix. The gas absorbs the heat. Although the flying gas caps are cool when the pressure releases. 2.5 exhaust is great and will are a difference. The factory export system was 2.5 from the manifolds back ending with a 3" muffler outlet to tail pipe and no cat. Muffler was the same just different in and out. Sound was the same just deeper and richer sounding .

Nikkormat · Post by **Nikkormat** » Thu Apr 09, 2015 7:53 am

I'm running 2 inch duals inside the frame rails with long (42 or 36 inch?) bullet mufflers. It runs between the transfer case and frame then back over the axle and around the spare tire to dump out on the passenger side. Its a bit loud but it sounds good. I would like to switch to turbo mufflers to quiet it down a little.

The exhaust system is important for a motor with an intake and any cam added in. AMC heads flow amazingly well stock. Add in a cam, intake, or head porting and you'll start to choke it out with back pressure. The force of the air coming out of my tail pipe tells me I need bigger, much bigger. But there isn't room for any larger pipe. Someone here has 3 inch duals outside of the frame, that sounds like an interesting setup to me.

REDONE · Post by **REDONE** » Thu Apr 09, 2015 9:05 pm

flawlessfailure wrote:I used a thrush welded muffler, big beefy mufflers full welded truck mufflers (like a flow master knock off) but half the price, it gives it a good throaty v8 sound and not obnoxiously loud, I like it a lot and only $40 at pep boys

I also have the Thrush welded and LOVE it. I went with the welded because I was still figuring out all the problems with the engine and it backfired a lot. Now that the problems are dealt with I just love the way it sounds.

Cheap Hobby wrote:If you need a y pipe have it made. The only one available is from Walker and it is thin, crush bent galvanized .

Double ditto. I used the walker y-pipe for the basis of my exhaust and I regret it. It looks and leaks like cheap nasty parts store "universal wrinkle toob exhaust pipe". If it was just my welds that leaked (I used 308L MIG) I'd own it, but the over filleted 3rd grader with TIG torch welds it came with leak too. I have no doubt it was made in China by a person with NO training or experience for social reasons we can't understand.

My dad on the otherhand had his exhaust made locally by a pretty reputable shop, "Lakewood Muffler". I've heard that people outside Denver order their stuff it's so top notch. He paid twice what I did, but it's all stainless steel. He had his done at the same time I built mine and his still looks amazing, despite colorado salting the roads. The fit and finish is miles above the Walker junk.

One thing I did that I highly recommend, I put a collector right in front of the cross member. The back half of my exhaust I made from Summit prebent pieces and it's still good. When I need to move the y-pipe it comes all the way out in one piece. This is super handy if you need to drop the oil pan, pull the trans, etc etc. (Ive had to do both since building my exhaust). I highly recommend the collector mod.

Tatsadasayago · Post by **Tatsadasayago** » Thu Apr 09, 2015 9:32 pm

I run a pair of 2" headpipes off before where the factory Y joined to a Dynomax dual inlet muffler, then 3" along the pass side to behind the R/R Wheel. Kinda growly for an old guy, but I kinda like it. The only drawback is the drivers side headpipe is kinda close to the transfer case as it goes over the top. Was this way when I bought the Jeep and works well enough I've left it alone.

Cheap Hobby · Post by **Cheap Hobby** » Fri Apr 10, 2015 2:50 am

Don't agree on the back pressure issue. We have dynod these engines built and stock with open, stock and headers less than 1% horse power gain with headers and lots of flame and noise from the open. Older Chevy s are far more sensitive to back pressure. I've seen these engines pulled fro ski boats and dropped in cats with no change in performance.

Modified a brand new 1980 limited for export to Germany defeated cat and installed factory export exhaust and returned for 49 state specs. Same power and speed. Slightly better mpg and much better sound. The only re I've has problems with back pressure is when the hat burned out and packed the muffler. Have seen issues with too big of system.

Josh d · Post by **Josh d** » Fri Apr 10, 2015 1:43 pm

Headman headers, 2.25" pipes into dual 2.25" in/single 3" out Flowmaster 50 series. Sounds great, runs even better!

FSJunkie · Post by **FSJunkie** » Fri Apr 17, 2015 11:49 pm

2" dual should flow the same as 2.5" single, because Pi times radius squared, and actually the single should scavenge better. 2.25" dual or 3" single should be good for a 401. 2.5" dual would be the max size. Single 3" is probably the cheapest and easiest option.

I don't buy into the whole backpressure deal, either. Let the cylinder heads and exhaust manifolds be the restriction. After that let it flow as much as it wants. I also don't think it matters much what muffler you choose for flow. If the pipe is sized right the muffler poses little restriction. I went from a straight-through Magnaflow (no internal restriction at all) to an OE-style muffler and noticed no change in how it ran.

The bigger the pipe, the noisier it will be, so a 3" pipe hanging out the back will tend to make a lot of noise. Might have to put two mufflers together in a row with a resonator near the tip to really quiet her down. The quietest mufflers will be OE-style mufflers if you can find something to fit. The next louder will be the universal fit stock replacement mufflers followed by turbos. After that you get into Flowmaster zone, then Magnaflow and Dynomax and ending with a straight up cherry bomb glasspack.

I like turbos when I want something to have some sound but not that I can hear while driving. Exhaust noise is for people outside the car to hear, not people inside, and turbos do a good job of giving the car a low rumble without the volume. Some of the more docile Flowmasters like the 50 and 70 series can be nice as well.

Tin Medic · Post by **Tin Medic** » Sat Apr 18, 2015 12:53 am

I'm running Doug Thorley tri-Y headers with 2.5 single pipe and a magnaflow muffler. Nice sound while driving and not to loud.

j2sax · Post by **j2sax** » Thu Apr 30, 2015 2:47 pm

I have 2 1/2 to a dual in/dual out crossover muffler from DynoMax (I believe) I much prefer ANY dual exhaust with a crossover than both banks firing on their own... really smooths the sound out without taming the beast too much. Many people do a separate crossover tube and 2 mufflers, which also works and takes less room, but under my 401 J10 was not an issue.

The duals into a large (3"+) is a better sounding option imho than the individual separate banks.

Tatsadasayago · Post by **Tatsadasayago** » Thu Apr 30, 2015 4:00 pm

I have essentially the same setup as you j2sax. What I noticed is while the low end is a bit throaty and bass-ish, by 2500RPM and above it quiets down to the point I can't hear any exhaust note over the wind and road noise--which is very tame now days with the insulation and carpeting.

The two 2.5"s into a decent sized muffler with a 3" outlet to behind the rear tire flows better than my heads can and takes up less valuable space under there.

DarkMonohue · Post by **DarkMonohue** » Sun May 03, 2015 9:47 am

FSJunkie wrote:I also don't think it matters much what muffler you choose for flow. If the pipe is sized right the muffler poses little restriction.

I don't think this is a universal truth. Some mufflers (like your Magnaflow example) pose no restriction whatsoever and flow as much as the pipe they attach to. Some others that fit the same size pipe (factory installed mufflers, cheap service-grade replacement units) are quite badly necked down inside.

You and your engine may or may not notice a difference in day-to-day driving, but it is definitely possible to choose a muffler that restricts performance.

If/when I find the time and budget, and chop through the taller weeds first, I'll build a nice 3" single system with a Hooker Aero Chamber muffler. I think they're pretty tough to beat for a nice "performance" sound without booming resonance. This is for a pickup, so that's less of a factor, but if it was in a wagon, you could add a 3" inline resonator after the rear axle to kill any unwanted frequencies.

tara · Post by **tara** » Wed May 25, 2016 9:32 am

some have experience the hot mad thrush mufflers ?
really wondering what to install in my 327. still got the OEM which sounds great but really too low and restrective

44bz · Post by **44bz** » Wed May 25, 2016 11:49 am

tara wrote:some have experience the hot mad thrush mufflers ?
really wondering what to install in my 327. still got the OEM which sounds great but really too low and restrective

I have the Thrush welded muffler behind my 327 and 2.5" pipes I think. Might be 2.25", I can't remember now. It's got a real decent hot rod rumble to it.

wewillsurvive · Post by **wewillsurvive** » Wed May 25, 2016 12:37 pm

I also have a thrush welded muffler 2.5" pipes into Flowmaster y that makes it all 3". The 2.5" maybe 2.25"... Either way it sounds good. If you find my exhaust thread the part numbers are all there as is a video of it running.

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