LS3 480 swap ... 2.5 or 3 inch exhaust?? Muffler suggestions?

[NovaSF]

Getting close to pulling the trigger. Exciting $&?@!!!! Gonna go with the LS3 480. Need to decide on exhaust. What's are your thoughts...? 2.5 vs 3 inch exhaust?

Car is a 1970 Nova. I'm gonna run long tube headers and I'm also going to have catalytic converters. Haven't decided on mufflers yet.

Would 3's be that much louder even with the cats on there?

Would like it to sound good/ not too crazy loud at idle and cruising speed but don't want it too quiet. No drone. My kids will be in the car with me half the time.

Many good muffler suggestions?

thanks!!!

[icemanrd19]

2.5 sounds great for me. Running dynatech muscle max exhaust which has super turbo mufflers

[piratebaseball]

What rear suspension are you running? If you are running a ridetech g bar, you can forget about running the exhaust over the rear axle out the back if you are going 3". You can make it work with 2.5" but it is a TIGHT fit.

[Later-A-body]

You could do a hybrid set up like I did on my project. I run 3" exhaust out of the headers, into dual 3" cats. The 3" exhaust continues into and out of an "X" pipe, then reduces to 2.5" about 1" before my 2.5" Borla mufflers. The 2.5" continues over the axle and out. It is a good compromise. I did not want a 3" due to the noise and also to minimize any fit issues.

[xavier296]

I'm running 3" on my LS3 with magnaflow mufflers. I ran the exhaust under the rear axle, and in 5k miles, have never touched them to the ground. I hit the vert brace often, but never the exhaust.

My car is loud BTW when on the gas, but pretty good when cruising. I bought some cats and may put them in just for the sound reduction.

Also, running hooker mid lengths instead of long tubes to work better with the tru-turn setup from ride tech.

[ragz]

Ls3,525hp , 2.5 stainless BlackWidow Pro 250 Venom,

[MAGONSTERZ68]

[QUOTE=xavier296;1264642]I'm running 3" on my LS3 with magnaflow mufflers. I ran the exhaust under the rear axle, and in 5k miles, have never touched them to the ground. I hit the vert brace often, but never the exhaust.

My car is loud BTW when on the gas, but pretty good when cruising. I bought some cats and may put them in just for the sound reduction.

68 convertible, Also, running hooker mid length as well, used full mandrel bent 3" stainless and routed out the over rear axle and dumps side of fuel tank. 525 HP LS2 467 to the wheels and didn't need 3" 2.5 would of done just as well with little to no loss of power and possibly even been a bit quieter.
originally used two warlock mufflers and was ridiculously loud at idle even with x balance tube so added two spintech muffs travers mounted between rear axle and fuel tank, completely mellowed out the idle but still rips at full throttle. Added electric cutouts just after 1st set of mufflers just in case i want to run straight pipe.

[NovaSF]

I ended up going with 1 7/8 long tubes and 2.5 inch MagnaFlow exhaust (I think they’re turbo mufflers). I also have MagnaFlow cats on it (the tiny ones , 200 mcell count).
The car is pretty quiet at idle and low speeds, screams at higher rpms. I kinda wish it
Was a little louder at idle but all and all, my head isn’t ringing after I get out from a long drive and I like that.
Overall I’m happy with it.