1997 K2500 GMC 7.4L

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.

Erik the Awful

Supporting Member
Supporting Member
Joined
Aug 9, 2019
Messages
7,624
Reaction score
15,541
Location
Choctaw, OK
The Harbor Freight flux welder doesn't do too bad on exhaust work. My wife bought me one years ago without asking - I would've told her not to. Soon after a friend brought over the exhaust from his Sentra that was cracked. It zapped it closed with no leaks, and I had almost no welding experience at the time.
 

Schurkey

Supporting Member
Supporting Member
Joined
Jan 14, 2018
Messages
10,970
Reaction score
13,759
Location
The Seasonally Frozen Wastelands
Was the other truck a diesel?
No. I think it was a '94 K1500 5.7L, the same truck I stole the front suspension from, to put on my '88 K1500. I'm thinking the muffler inlet, and the tailpipe are 2 3/4" tubing.

At any rate, it was a single-catalyst exhaust that the Treasure Yard had already cut the catalyst from--so I unbolted everything that would have been behind the cat. Slid the hangers into my truck's mounting points like it was made for it. I cut some pipe ahead of the muffler, and welded-in a Y-tube, which I then welded to the stubs coming out of the twin catalysts on my '97.

No doubt this would not work well under load at higher RPM--but I use this truck to plow snow. "High rpm" is just not an issue for me.
 

Kruzin66

Newbie
Joined
Aug 2, 2021
Messages
1
Reaction score
2
Location
Minnesota
I rebuilt the engine in my 96 Suburban and tried to find a way to get rid of the restricted factory 1-7/8” Y pipe without going to headers. Solution I came up with was a GM Y pipe from Jegs 555-31002 which is two 2-1/2 into a 3” and then a Walker 44840 intermediate 3” pipe (you may need a different part number depending on your wheelbase, this is one is 32” long) that bolts directly to the Y pipe flange and gets you past the crossmember. It has the stub on it to fit into the factory hanger. (I had to move the factory hanger forward in the frame to the next set of factory holes) I then installed a Flowmaster 3” single inlet and two 2-1/4” out to dual tail pipes. If you went with a single 3” outlet, it would line up with the factory tailpipe if that is what you want. I ordered O2 sensor bungs 555-30740 and drilled holes in the Y pipe and welded them in so I could keep the factory sensors in the stock location. Used stainless band clamp 555-30733 so I could take it apart if it didn’t work out. So far so good. No rattles or leaks. Hope this helps.
 

RedBurb

OBS Enthusiast
Joined
Apr 1, 2021
Messages
70
Reaction score
60
Location
California
I have a pesty exhaust leak at the main square flanges just downstream of the driver's side CAT (reference PN 4731 in the diagram posted above). I can't seem to get the flanges to align and tightly sandwich the gasket. I loosened the three nuts holding each pipe to its respective exhaust manifold in order to provide enough "play" to align the flanges but even this was no-go. Could it be that the flange is bent? I took it to a local muffler shop where the old timer said aligning the flanges can be a royal PIA. The flange only has three bolts to do the job across a faily large and busy surface area. He suggested cutting the flange out and simply welding the two sections of pipes together. Has anyone on this site done this before ----any issues with removing the flanges? Is there a better way??

(BTW --My '97 L29 has (4) O2 sensors----one on each exhaust pipe approx 10" from the exh. manifold connection and one after each CAT)
 
Last edited:

yevgenievich

I'm Awesome
Joined
Jan 21, 2021
Messages
934
Reaction score
1,505
Location
TX
Something bent or moved. One way is to simply cut the pipe before the flange, and then reweld after flange is bolted on correctly. That would relieve extra pressure. If flange is not straight and bent, then a different connection would need to be made( either weld pipe together or install different flange)
 

RedBurb

OBS Enthusiast
Joined
Apr 1, 2021
Messages
70
Reaction score
60
Location
California
Something bent or moved. One way is to simply cut the pipe before the flange, and then reweld after flange is bolted on correctly. That would relieve extra pressure. If flange is not straight and bent, then a different connection would need to be made( either weld pipe together or install different flange)
Thanks, I'll ask the muffler guy to try the partial cut relief(s)first --it might take one cut per pipe.

I hate the idea of removing the original stout flange. In my world removing it will undoubtedly create another set of problems e.g., a cracked weld or pipe somewhere else along the system due to additional flex and vibrations. Or a full engine eject at 70 mph,,,

It just occurred to me that possibly part of the alignment problem is lack of shoulder bolts. The bolts I found on the unit are full threads ---I believe they are 3/8x16 by 3/4" long. Are these original bolts?
 
Top