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351w going in my YJ but what muffler?

1K views 13 replies 7 participants last post by  89YJBuilder 
#1 ·
So I, as usual, am planning ahead. Once I get the engine built and installed I am obviously going to need exhaust. I figure 2.5 or 3 in tube. I like Maganaflow mufflers but there are other quality units out there. I do not want it to be any louder than necessary. The exhaust will, obviously, be short and therefor louder than a pick up with the same size pipe and muffler. So what are the recommendations? I am currently looking at a Magnaflow 11229 but have no idea how loud it will be. I don't want loud.

I am not doing a "wild engine build." .30 over very close to stock, the biggest upgrades will be Edelbrock E-Street heads and mustang injection. Maybe a low end Comp Extreme 4X4 cam.

Any way thanks for the info.
 
#2 ·
I would go as quite as I could, that motor really wont lose much power. There are plenty of muffler choices, all depends on how loud you want it, that's kind of a personal preference. 3" pipe might get a little tight depending on how you run it and will be a little louder. You can never go wrong with Magnaflow, I would just pick the quietest one they make, Dynomax makes some that still perform well but are on the quieter side. I have also read, not sure if true, but going to a single pipe out the back instead of duel will help reduce drone, maybe others hear can clear that up.
 
#4 ·
in 100% stock form the engine has way more power than the 2.5 so not too concerned with cutting performance. I'm not going to intentionally choke it though.
I had a 78 Chev short box that had an L88 in it that I warmed a bit. The exhaust ran from long tube headers to cross pipe and dual Flow Master 44s. 3" pipe and dumped right in front of the rear tires. It made the stereo and CB useless. Hated it! it would boil the 35s in 4wd on dry pavement, but too loud. It was fun though I couldn't keep drive shafts in it. I was 24 so that didn't help either.
44 now and quiet is good.
 
#5 ·
A good 2.5" single system with a fully welded steel muffler (and catalytic) is a great choice for a mild V8 like your 351W. The 2.5 inch system has a higher overall velocity that helps port scavenging on a short wheel base vehicle like a Jeep.
 
#6 ·
I had the same thoughts in my build. 330hp Vortec headed 5.7. I went with ram horn exhaust manifolds, with 2.5" downpipes, into a 3" y-pipe, then a 3" resonator, then 3" dynomax muffler that has a 2.5" tailpipe. If you do the math based on the equation PV=nRT where we want pressure constant, volume and temp are the variables. As temp decreases, so does volume on a gas (in degrees K not C or F). My calcs were that the temp drop from the inlet of the 3" pipe (as it goes through the resonator and muffler) would be slightly more than the same ratio of dropping from a 3" diameter to 2.5" diameter pipe. Thus minimal pressure change throughout the system to exit which should keep low end torque numbers up.

The large "fart-cans" on the back of some imports only increase sound and probably hurt performance... They do not understand science... Another concern to keep sound down is to make sure that the tailpipe exits away from the jeep, not under it.
 
#7 ·
Wow way more info than I was expecting. Thanks for the lesson. I really can use it as I truly had no knowledge of the way that all worked out. I usually just did a big pipe to big muffler previously.
 
#13 ·
I have a 302 and wanted to do duals out the back, but it would have been tight clearance. Instead I went with duals into a single 3" output. It's kind of tight but fits and I'm happy with it. I'll try to find a pic of it
 
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