93ChevyVan

My 21 year old muffler is finally saying goodbye. Has anyone installed a flowmaster or magnflow muffler on a G20? I am trying to decide what would sound the best and do the MPG thing for me.

canucklehead

I had a new magnaflow put on my 2002 express and it has the vortec 350. It made a difference for power, minor but noticeable. The problem is there was a huge drone at about the middle of the power band. Every time you got to the upper part of the gear befor the gear change, the harmonic drone was so bad that it hurt your ears in a large open van. I had to take it back and have a resonator put on behind the muffler. It fixed the drone, but cost be another 130 bucks, which peed me off for sure.
Since then its been great. Bette sound, and power. No fuel economy change to speak of.

greenfire

I believe Flowmaster has an SUV model that prevents drone.

200OZ

I ran a Flowmaster Super 44 series with out a converter on my '95 G30 with a 350 and 4L80E. Lots of fun. Didn't notice any power increase, but my mileage went down....! It sounded too good to keep my foot out of the loud pedal. I used the tail pipe of a '87 G30 van because the pipe diameter is 3", as apposed to the '95s 2-3/4". Flowmaster makes a 70 series that might fit the bill to keep noise a bit lower. Make sure to run a full exhaust, that's a good way to reduce exhaust drone, and a resonator will help even more.

93ChevyVan

My 1993 G20 has a 305 and 4L60-E and the cat converter is gutted (not needed in NC emissions because of the year). When I got it, the tail pipe was rusted out and I replaced it with a 2 3/4 pipe. Probably should've put a bigger tailpipe on.

Thanks for the advice. Gives me somethings to consider now.

canucklehead

If you go without a cat, won't you mess up the emmissions sensors? Your fuel injection will be off. Unless there is a tune you can apply.

spaceblonde

i think there just precat O2 sensor

93ChevyVan

It passes emissions with flying colors and nothing seems to be affected by having no cat converter, just a bit more power than it used to.