Magnaflow mufflers on 8.1

AmericanMuscle · May 14, 2005

Just had two 2.5" stainless Magnaflow mufflers installed inplace of the factory muffler on my truck. It sounds awesome!

It's very quiet at idle, but the moment you hit the gas, you can tell it has exhaust. It's really deep, and loud when you romp on it. At highway speeds, it has a nice mellow rumble with no interior resonance.

My only complaint so far is when towing a trailer in Tow/Haul mode and the engine is engine braking while decelerating, you get a few pops out of the exhaust now and then, but its really no big deal.

Don't know yet how gas mileage will be affected.

I don't appear to have lost any low end torque (my original concern with going to a free flowing exhaust), and as a matter of fact it feels slightly stronger throughout the entire powerband.

Overall, I'm very happy with the Magnaflows

I'll try to snap some pics and figure out how to post em...

dannyukonxl · May 15, 2005

that is awesome, i think im going to do that setup, which mufflers did you use, im still deciding on which cans to use but im set on 2.5 inch pipes and 4 inch tips

AmericanMuscle · May 23, 2005

Alright, I'm reporting back after putting about 2000 miles on these mufflers (I drive alot).

Dannyukonxl, the part number is 14326. They are a 4"x9" SS "oval" muffler w/ 2.5" center inlet / 2.5" offset outlet.... and I'm running two of them into the factory tailpipe. If the suburban's exhaust is the same as the HD's, you could run true duals if you wanted to.

I'm still enjoying the mufflers and would put them on again. My only complaint so far is in my truck is lugging down at 1300-1700rpm in 5th gear (40 to 50mph), the exhaust note is so smooth it drones more than it thumps. The easy fix is give it a little more gas and it gets aggressive again. Its really not that big of a deal. No exhaust system is going to sound perfect. What I believe it is, is the resonance is just right under the truck to create a droning sound in the cab. Outside I think it still sounds good (how could an 8.1 not?). This seems to have formed after the mufflers have loosened up a bit.

Idling, the exhaust has some "fuzz" to it. Kind of like a Vortec 350 has if you put loud pipes on it. The moment you touch the gas it's gone, but you do hear it idling if your next to the pipes. Also not that big of a deal. I'm just a perfectionist.

I absolutely love how it sounds accelerating in town and running down the highway. Anything over 2000rpm sounds really good.

k3500 · May 24, 2005

Did you notice any change in your fuel mileage or are you still enjoying the new sound with your right foot?

High Mileage · May 24, 2005

Hey Muscle,

You'll continue to enjoy them. I put dual 3" x 18" long magnaflows on my truck last December. Had to be custom since nobody offers a kit for a regular cab truck. Per the installer's recomendation I had a crossover pipe installed just ahead of the mufflers. 2 1/2" pipes were run from the mufflers to 4" tips droping out of each fender behind the duallys.

My resonance occurs between 59 and 61 mph. Not so bad that I wouldn't leave the cruise control set there.

My first day after the work had been done I was kicking it coming out of a tunnel in Washington DC and actually scared myself. Thought I'd been surround by the Hells Angels. You've got to find a tunnel or a decent overpass to kick it under.

By the way,, my installer is located in Woodbrige, Va and he does excellent work.

AmericanMuscle · June 1, 2005

k3500, I actually have seen about a .5mpg gain!

I normally drive 85 to 87mph on the highway. With the exact same amount of weight in the bed and travelling the same roads, I'm now getting 10.5mpg where I was getting 10.0mpg before the exhaust. No other changes. This is over a lot of tanks of gas too. This isn't a one-time deal.

I just recently got my best tank, 10.7mpg. I typically carry about 600lbs of equipment in my bed, and drive fast.

I got 10.2mpg going consistently 90mph over a stretch of road I used to get 9.5mpg before exhaust.

Around town I don't see any mileage gains, but thats because I'm usually on the gas.

High Mileage, I mashed it today under an overpass and it sounded rowdy! I was right next to some kid in a rice-rocket and I could see him look over shocked through my side mirror. He got an ear full.