Magnaflow Muffler Question

[hpracing10]

I am going to weld in new magnaflow muffler in place of my stock muffler on my truck, 2003 silverado 1500 Z71. The muffler I have picked out that closely matches the dimensions of my stock muffler is part #12286. It is a 5x8in oval, 24in long and has Center/Offset 2.5in inlet/outlet. The stock pipe on my truck is 2.75in so I am going with the 2.5in inlet/outlet so I can slide it inside the stock pipe and weld it up. My quesiton is this: On my stock muffler, the inlet is more towards the bottom center, and the outlet is more towards the upper left. Will the magnaflow muffler fit right in there, since it is center/offset inlet/outlet, or will I have problems because on my stock muffler the inlet is towards the bottom and the outlet is more towards the top? Thanks for any input! Just want to be sure it will fit ok before I order it.

[05silvycrew]

might have to tip it, instead of laying it flat like the stock muffler. I can't tell you for sure if it will line right up, sorry

 

That's what they had to do with mine. I got a 5X11 case, 22" long, 3" center/3" offset. Mine's tilted up toward the driveshaft and down toward the fram.

 

if you're looking from the rear axle it looks kind of like this \

[hpracing10]

Ok, that's what I figured I would have to do which is fine but I wanted to get someone else's input. Also, I am new to aftermarket mufflers but I am set on magnaflow because I have heard first hand they are quieter in the cab than flowmasters. I have been told that the longer the muffler is, the quieter, is that true? So a 24" would be quieter than an 18" for example? Thanks

[oldscsc]

Ok, that's what I figured I would have to do which is fine but I wanted to get someone else's input. Also, I am new to aftermarket mufflers but I am set on magnaflow because I have heard first hand they are quieter in the cab than flowmasters. I have been told that the longer the muffler is, the quieter, is that true? So a 24" would be quieter than an 18" for example? Thanks

 

Yes the bigger the muffler the quiter it will be. Also, I bought a 2.5" in/out for my truck (stock 2.5" exhaust) and they just kinda flared the inlet and outlet pipes the fit around the stock pipe (might be a better idea than buying it 1/4" too big).

[hpracing10]

That is a good idea, I may look into that as well. Only thing is, the stock size exhaust pipe on my truck is 2.75" and I couldn't find a magnaflow muffler with a 2.75" inlet/outlet they are all either 2.5" or 3". The wall thickness of my stock pipe is 1/8", so times that by 2 and you get 1/4", so going a 1/4" bigger or smaller would work depending whether I wanted to go on the outside or the inside of the stock pipe. Thanks for the replies! Anyone else have any other advice I may need to know?

[nickvrebel]

get a 3" in/out center to center and it will fit just fine

[JAMIEZ71]

Go with the 3". I wouldn't restrict your factory exhaust by going smaller. I have the 14" Magnaflow and it's pretty quiet so I could only imagine that the 24" would be really quiet. Probably won't even hear it.

[05silvycrew]

Ok, that's what I figured I would have to do which is fine but I wanted to get someone else's input. Also, I am new to aftermarket mufflers but I am set on magnaflow because I have heard first hand they are quieter in the cab than flowmasters. I have been told that the longer the muffler is, the quieter, is that true? So a 24" would be quieter than an 18" for example? Thanks

 

It also depends on how big the case is. a 24" round case (new age glasspack) might actually be louder than a 18" 5X11 case. The idea is, the bigger the case the more sound absorbing material can be packed inside it and thus more exhaust noise cancled out. they're all going to be about the same, but you are right, in generally if the case size is the same the longer muffler = quieter

 

I got the biggest one I could find (see post 2 for size) and am very happy with it. at idle or cruise, there's just a hint of something "not quite stock". under light acceleration it starts growling. under heavy acceleration it unleashes the exhaust note. smooth, deep, and mellow....exactly what I was looking for.

[hpracing10]

Thanks for all the replies. Thats exactly what I am looking for too, something that sounds just a bit different at idle/cruise but not deafening in the cab, yet when I get on it I want to know it is there. I was up under my truck tonight and it looks like a center/center would work but I think I can make a center/offset work even better so I went ahead and ordered a 24"x8"x5" case with 3" inlet/outlet center/offset. I'll let everyone know how awesome it is as soon as i get some free time to install it!

[apierce918]

where did you order it from? I Was going to order one this weekend, and autoanything.com has a 6x18 as their biggest which i figured would be fine but i havent really crawled under my truck to measure what i will be cutting out

[05silvycrew]

keep us updated when you get it installed! I think you'll love it!!!!!

[hpracing10]

I ordered the muffler off of Ebay for $90 and free shipping. That's a pretty decent deal considering the muffler part#12289 that I ordered is listed everywhere else for about $105. Should be here by the end of the week I am hoping and I will get it installed and provide an update!