We knew when we bought this truck the driver exhaust manifold was cracked. This weekend I replaced that and "upgraded" the exhaust.
After I removed the back 2 bolts, this piece just fell out of the engine bay.
The valve cover leaks as you can see with the oil on the broken piece.
Then, this piece came out with the y-pipe.
So this 350 had the extremely rare 3 piece exhaust manifold.
This was the first time I ever saw these things that I asked about above.
The interesting thing is the nicer looking one on the right came out of the busted manifold. So it seems like someone maybe replaced the "donut" gasket. It had to have been before the broken manifold because the one piece would have just fallen out. Maybe they broke the manifold putting the y-pipe back on? I just wonder how the manifold got so busted up. The exhaust is all old and shows no signs of being smashed.
Speaking of the exhaust system, here's the high performance setup that was in there.
Yes, it was y-pipe into single exhaust. Not a big deal except that it has maybe 2.5" up to the muffler and then kinked bend 2.25" tail pipe. Here are the other gems I found with the exhaust system.
Note the odd use of square nuts above.
Good old soup can & bailing wire muffler patch. Some other random material added for good measure.
Cheap flex pipe mounted right over old rusty tail pipe with a cool tip added for effect.
It does have a typical rear main leak so I thought this shield on the y-pipe was funny and yet also at least a little clever.
New manifold from China.
I noticed when I did the removal the front manifold bolt was loose. Problem was it was just a bit too short to reach the threads with the power steering pump bracket. I had to scrounge up a bolt; only thing I found long enough was a left over ARP bolt.
For the new exhaust I cut the 2.5" single pipe off the y-pipe and added a short piece of 3".
Then it's single 3" out through a Magnaflow. This will be the third truck for this muffler. It was in the K5, then the crew cab with the TBI350, and now this 73.
You can see my custom Frankenstein exhaust made up of pieces welded together. I used most of a 5' straight and half of a mandrel U-bend that was left over from Nate's red K5 exhaust project.
You can barely see my bit of cheating "hack" work to make it line up where I wanted. There's a spot near the left side of the photo where I put a pie slice in the straight run before the hanger. Before I did that, the hanger was hitting the frame and the muffler was hitting the e-brake brackets. I took about a 1/2" wedge out and bent the pipe a little. Then used the wedge to weld the pipe back together.
It worked out perfect and the tailpipe even hit the hanger just like I knew what I was doing. I didn't get a picture of the tailpipe because I need to get a different hanger type. The exhaust ends with a turn down just in front of the rear axle.
I was thinking about replacing the Magnaflow with the Thrush welded muffler that comes highly recommended by
@Bent77 but the MF was free. I still might get the Thrush if I can verify the offsets will line up with where the Magnaflow sits.
), then just this weekend I picked up a Thrush welded muffler. It just has a turndown right after the muffler just before the rear axle...and boy ol boy, it is the sweet spot now. It has a nice low tone to it at idle, and sounds real good off idle, and even higher RPMs is loud enough for people to look and say, "What the freak is under the hood of that boat!?!" but not loud enough that I can't just cruise down the road without being able to hear my wife next to me.
