Exhaust

[91Subbed]

When up grading to headers and dual 40 series flowmasters is it necessary to reinstall the cataylac converters? Other than emissions reasons?
1991 suburban 350 2wd.
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[tobiahr]

you will have to have the cats installed to pass inspection. IMHO thats the only real reason to install them.

[Edahall]

Originally Posted by 91Subbed

When up grading to headers and dual 40 series flowmasters is it necessary to reinstall the cataylac converters? Other than emissions reasons?
1991 suburban 350 2wd.
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The only other reason I can think of is to pass smog inspection and to help tone down the noise. Dual 40 series without CAT's is going to be very noisy.

[91Subbed]

Good noisy or bad noisy? I'm no worried about emissions.
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[Edahall]

Originally Posted by 91Subbed

Good noisy or bad noisy? I'm no worried about emissions.
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Bad noisy

Tip: Install a good quality glasspack in place of the CAT with the Flowmaster 40's behind.

[91Subbed]

Glasspack? Wouldn't it be even noisier?
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[Edahall]

Originally Posted by 91Subbed

Glasspack? Wouldn't it be even noisier?
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No combine glasspacks and Flowmaster 40 series. You would use 2 glasspacks up front and 2 Flowmaster 40 series behind. Glasspacks don't add noise. They remove high frequency noise while the Flowmasters remove the low frequency noise. Using both types of mufflers in tandem is very effective in noise reduction compared to just using 1 muffler type.

[91Subbed]

Yeah right now I have a really deep tone sounds good but I have lots of vibration.
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[Edahall]

Originally Posted by 91Subbed

Yeah right now I have a really deep tone sounds good but I have lots of vibration.
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What's your current setup?

[Edahall]

Here's a photo to demonstrate what I mean. I replaced the CAT with glasspacks (up front) and replaced the (very restrictive) rear muffler with a Flowmaster. The only difference in your case would be that you would have duals.

[91Subbed]

I don't have pics but, I have headers with 2 1/2" reducers with 2 flowmasters located under my back seats.
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[Edahall]

Originally Posted by 91Subbed

I don't have pics but, I have headers with 2 1/2" reducers with 2 flowmasters located under my back seats.
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If your issue with the current setup is too much noise / vibration, install some glasspacks wherever there is room (it can be behind the flowmasters or in front) and that should take of that issue.

[91Subbed]

Thanks man appreciate the help!
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[Edahall]

If you install in H-pipe or X-pipe, that'll also help with the noise and make the exhaust system even less restrictive.

[motornut]

i'd throw the 40 Flows in without(like mine with Hpipe)...but you can leave room to try it later
with a 305 it's a not bad rubble to idle with,great on the heavy pedal