Muffler for 3800sc (Page 1/1)
pontiacfierokid1985 SEP 29, 09:39 AM
Can people provide videos and part numbers for a muffler to go with on my 3800sc build I’m getting all parts in order dropping cradle out today I know tons go with the spin tech muffler but are there any other out there that will be the same size in diameter as the stock fiero one to fit up in front of the trunk. I don’t want to cut my trunk out so that isn’t a option here I’ll be using the stock manifolds and cross over if this helps and I want it to be at least a 2.5 inch exhaust so it can flow somewhat decent
Dennis LaGrua SEP 29, 06:39 PM
We use the Spintech crossflow muffler on the 3800SC swap. Spintech will supply one with any size inlet and outlet pipes that you specify. We've used the 13" L size with a 3" In and two 2 1/2" outs that we necked down to fit the Fiero dual trumpets and also the same muffler with a 2/1/2" in and dual 2" outs to fit the Fiero exhaust ends. That was on a 4.9L Cadillac swap. We tried the Flowtech afterburner but it was too noisy for my taste. The Spintech is a non-restrictive design but not overly noisy. We also chose that brand as no trunk cutting is required. Got to have that trunk as my wife likes taking 13 pieces of luggage even for an overnight trip.
darbysan SEP 30, 10:48 AM
As an alternative, I used the Dynomax 17638. It's slightly larger than the Spintech, but it will fit without cutting the trunk. It's tight on my install, because I also have a Magnaflow Cat installed. After my first install, I decided to modify the trunk just a bit, to be able to raise the muffler up just a bit. It does involve cutting of the trunk, but I only cut off the small slanted portion at the very bottom of the trunk, maybe 2 1/2", essentially making the trunk floor flat vs slanted toward the front of the car. No real loss of space inside, it was pretty easy to do ( no welding), and only took about 1 hr. Keep that in mind in case you find the fit is not what you were looking for.

Here's a picture of the first install, before cutting the trunk. You can see the muffler hangs down about even with the cradle.



Here's a picture of the chunk of trunk cut out. You could probably get fancy and just cut three sides, and then bend it up and re-attach it at the front of the trunk. I chose to make a plate that fit inside the trunk, bent up the cut edge all around the trunk about 1/2", and then pop-riveted the new floor in place. A little sealer and you're done.



Here's the final install. Cutting the trunk allowed me to slant the muffler enough so that it is above the cradle.



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'87 GT , '00 3800 Series II SC, 4t65e, Vue Power Steering. (SOLD)