What size exhaust is stock on a 2003 Silverado 5.3L?

**beatle78** · 06-26-2008, 05:30 AM

Hi guys,

Does anyone know what size exhaust comes stock on my 2003 Silverado w/ 5.3L?

I think I'm about to pull the trigger on a Magnaflow universal muffler :)

thanks!

**Cowboy Silverado** · 06-26-2008, 02:03 PM

If you a referring to the pipes I believe it is 2 1/2 inch pipe at least that is what it was on my 01.

**beatle78** · 06-26-2008, 03:51 PM

yes, thanks. I was referring to the pipe size.

I'm look563ing to get a Magnaflow universal muffler and needed to know the size.

**00silverado2wd** · 06-26-2008, 04:57 PM

I had a 3" magnaflow put on my 2000 silverado

**shinychevy** · 06-26-2008, 05:51 PM

I think the stock size is 2-3/4", kind of an odd size. I just ordered a SI/SO universal Magnaflow muffler myself (#14589), can't wait for it to arrive. Got it from hottexhaust.com.

**beatle78** · 06-26-2008, 06:39 PM

Originally Posted by shinychevy

I think the stock size is 2-3/4", kind of an odd size. I just ordered a SI/SO universal Magnaflow muffler myself (#14589), can't wait for it to arrive. Got it from hottexhaust.com.

yah, I just measured it. I measured 2-3/4" outside diameter and 2-9/16" inside diameter.

Are exhaust pipe diameters measured from the outside or the inside of the pipe?

OK, so how do you fit a 2-3/4" stock pipe into a 3" muffler?

Are you just cutting out the old muffler and piecing in the new muffler?

thanks!

**beatle78** · 06-27-2008, 06:12 PM

Do they make 2-3/4" to 3" adapters for exhaust?

I would need 2 if I cut out the muffler and put in a Magnaflow :)

**Underpowered** · 06-27-2008, 09:15 PM

most use a 3" muffler and just have the gap welded up, atleast thats how i did mine. bought a 3" muffler and just welded up the gap to seal it.

if you take it to an exhaust shop they can make an adapter to go from 2 3/4 to 3" for you.

**beatle78** · 06-28-2008, 04:57 AM

Originally Posted by Underpowered

most use a 3" muffler and just have the gap welded up, atleast thats how i did mine. bought a 3" muffler and just welded up the gap to seal it.

if you take it to an exhaust shop they can make an adapter to go from 2 3/4 to 3" for you.

ahhhh ok. Yah that makes sense. So they could just fill the gap with weld and skip the adapter altogether, right?

**kaycee** · 06-28-2008, 06:16 AM

A good shop will expand the end a little so it slips over and then they weld it up.Yes they do make an adaptor to match them up

**Underpowered** · 06-28-2008, 09:42 PM

Originally Posted by kaycee

A good shop will expand the end a little so it slips over and then they weld it up.Yes they do make an adaptor to match them up

kinda hard to expand a pipe that is already on the truck ain't it? unless you get a muffler that is already a smaller size, you can't expand it.

however, the shop that origionaly did mine did say that if i bought a 2.5" inlet they could expand it to work with teh 2.75 but have actually split a few mufflers trying this.

**gitingrdone** · 06-28-2008, 11:37 PM

When i got my exhaust the guy was putting 2.5" on and i asked about it being smaller then stock size. He said that GM uses an odd sized 2.75" pipe to minimize alterations to the exhuast. I dont know if that was true or not. The just welded the gap up like you guys were saying.

**kaycee** · 06-29-2008, 07:09 AM

A little pissy r we,I was just refering to how some do it

**beatle78** · 06-29-2008, 05:02 PM

Originally Posted by kaycee

A good shop will expand the end a little so it slips over and then they weld it up.Yes they do make an adaptor to match them up

ok sweet. I'm too cheap for an exhaust shop. I will probably order the muffler cut out the old one and get the adapters to attach the new one.

Then when I visit my cousin, I'll have him weld it for me....

Can you weld stainless? Or do you need to braze it?

**beatle78** · 07-01-2008, 06:01 PM

Does anybody know if you can weld stainless? Or do you have to braze something like that?

**Underpowered** · 07-01-2008, 08:52 PM

stainless can be welded.

**Chevy4thewin** · 07-02-2008, 01:20 AM

Your local auto parts store should have some kind of adapter for your setup.

**beatle78** · 07-02-2008, 05:27 AM

Originally Posted by Underpowered

stainless can be welded.

Originally Posted by Chevy4thewin

Your local auto parts store should have some kind of adapter for your setup.

Thanks guys. I do want an adapter, but then I would like to have it welded. Then I guess the best thing to do is to put some high temp paint on the welds so that they do not rust, right?

**bhutton86** · 04-20-2011, 05:54 PM

i got the same issue, i have a 02' silverado, got a flowmaster cheap for 25 bucks but its a 2 1/2 in and out. what size adapter would fit? the id is 2 1/2 on the pipes and the muffler.

**dundee57** · 04-20-2011, 08:06 PM

My muffler shop cuts a little off the inlet on the muffler so the inlet is just large enough to fit over the pipe then welds it up.

What size exhaust is stock on a 2003 Silverado 5.3L?

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