I'm a parts manager at a GM dealership and we just installed a GM crate 650hp/650tq LT4 6.2L supercharged, same as the C7 Z06 corvette engine into a 2017 Silverado 1500 reg cab standard bed. I had to re-use the stock 5.3 manifolds because of clearance issues. The techs (4 master techs) in the shop are advising me to leave the stock 5.3 cats and exhaust so it'll be a sleeper. 1: the customer wants it to have a deep sound and be a little louder. 2: I know that 650hp needs a lot more than a 2.5" single exhaust. I've read many muffler comparisons with cfm charts and they all say you need at least full 3" duals to accommodate the 650hp this truck is producing. The customer and I would both like to keep the bank 1 and bank 2 cats and delete the third cat. The pipes behind both cats are around 2.75" where they collect before going into the 3rd converter. I was thinking we'd chop it off where those pipes come together before the 3rd cat and run true 3" duals (2 mufflers) or a 3" dual inlet/dual outlet (1muffler). I'm just not sure which muffler to choose for both the sound we want and which one will give us the best performance. Price is not an issue whatsoever. Any advice would be greatly appreciated!

 

why stock 5.3 manifolds ? no clearance for arh or kooks ?

if you have clearance i would suggest kooks lts with green catted y-pipe you can run a muffler and resonator if you need to tune the sound down

 

Agreed Kooks Long Tubes with the green catted y-pipe and resonators as needed

 

At first I was going to say Borla Touring, but in checking their muffler specs the largest diameter they make in Touring is 2.75 inlet/dual 2.25" outlet which would work better than stock, but if this were my truck I'd be shooting for 3" all the way out. Their S-Type mufflers are a little more aggressive.

https://www.borla.com/chevy-silverad...haust-systems/

 

No room for headers. We wanted to run them but an oil cooler line and the engine mounts cancelled that idea. Thanks for your responses.

 

Since you're a dealer who sounds like you do a lot of performance stuff, you probably have a lot of take off parts laying around. If you have the stock exhaust off a duramax truck, put that on there. It's about 3.75" I believe and it will be much better than the stock gas truck exhuast and they sound pretty good on the gas motors.

 

What about a factory 6.2 exhaust? I know its 3.5" for most of it.

 

you can also call kooks or any other good shop for a custom work .

 

Interesting the motor mounts needed to be changed enough to cause issues

 

I would look into that as well.

If it's anything like the earlier trucks, It's probally a true dual back to the muffler.