5.7 Exhaust to a 7.4 Exhaust

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

alpinecrick

I'm Awesome
Joined
Jun 12, 2015
Messages
1,614
Reaction score
1,695
Location
Western Slope of Colorado
'96 K1500 ECSB 5.7, 4L60E.

Some time ago there was a thread and one or more members said the 7.4 exhaust system with its larger diameter will bolt up to a 5.7 half ton truck. This is all the exhaust including cats to the muffler. Do I remember correctly or is it not so?
 

Supercharged111

Truly Awesome
Joined
Aug 20, 2015
Messages
12,614
Reaction score
15,239
7.4 is a bigger motor so I doubt that. A 5.7 exhaust from an 8 lug truck would absolutely bolt up and is a larger diameter.
 

alpinecrick

I'm Awesome
Joined
Jun 12, 2015
Messages
1,614
Reaction score
1,695
Location
Western Slope of Colorado
7.4 is a bigger motor so I doubt that. A 5.7 exhaust from an 8 lug truck would absolutely bolt up and is a larger diameter.

So you're saying the 2500 and 3500 5.7 exhaust is larger diameter than the 5.7 1500 trucks?

So the 5.7 exhaust from the 2500/3500 is 2 1/4" just like the 7.4 exhaust? But the flanges that bolt to the manifolds are different between the 5.7 vs the 7.4 ?
 

Schurkey

Supporting Member
Supporting Member
Joined
Jan 14, 2018
Messages
10,967
Reaction score
13,746
Location
The Seasonally Frozen Wastelands
Buddy of mine has a '97 K2500 with 7.4.

I just bought one a week ago.

He was telling me that the best exhaust mod he did was to SCRAP the OEM muffler, because it had 2.5" inlets, but was restricted down inside to 2" or 2.25". You'd never know unless you cut it apart--or it blew apart--and you looked inside.

Replacing the original muffler with a pair of genuine 2.5" inlet/outlet (and internal passages) mufflers made more difference than his Gale Banks fancy-ass headers and new converters.

MY truck has already had the OEM muffler replaced, they reduced the pipe size from 2.5" to 2.25 by welding-in stub pipes, then installed a muffler with dual 2.25 inlets and dual 2.25 outlets--but the muffler is completely blown apart, so I need exhaust work pretty bad, too.
 

454cid

Sooper Pooper
Joined
Sep 5, 2010
Messages
8,003
Reaction score
8,885
Location
The 26th State
It's my understanding that the Vortec exhaust varies with GVW not V8 displacement. It's just that there are no lighter GVW trucks with the 454. I have never verified this myself.
 

letitsnow

I'm Awesome
Joined
May 5, 2018
Messages
1,684
Reaction score
2,460
Location
MN
7.4 is a bigger motor so I doubt that. A 5.7 exhaust from an 8 lug truck would absolutely bolt up and is a larger diameter.

My 99 3/4 ton with a 350 had dual 3" OD exhaust (and dual cats) back to the dual 3" intake muffler. That muffler had a single 2.5" outlet for the tail pipe. Just FYI, if anybody is looking to do a cheap swap.
 
Top