How I replaced a 521 exhaust system
Posted 15 March 2014 - 10:50 PM
I used this truck, as a model.
I know replacing an exhaust system is a lot of work, and there are muffler shops in almost every town and city. I did get a quote of about $300.00 to replace the exhaust system on Ratsun. I have spent about $238.00 on parts, pipe, muffler, hangers, clamps, and another $46 on a tail pipe expander. but I have quite a few parts left over, and the second exhaust I build should require spending maybe another $100.00.
Ratsun had a stock sized exhaust system, and I had a 2 inch system put on Dragon a long time ago. Most of Dragon's exhaust system was rusted out, but the collector and a short piece of pipe, with a 45 degree bend were usable.
I ordered four 4 foot pieces of pipe, and a kit of two 45 degree, and two 90 degree bends, from this company. http://www.mandrel-bends.com/catalog/
Here are some parts you will need to get from your local Nissan dealer.
The gasket is obvious. The nuts are a type of stainless steel that does not seize to the manifold studs easily. I used these nuts on Ratsun, when I put the engine in it, in 2011. I cannot remember when the last time I removed the exhaust system from Dragon. Long story short, no broken exhaust manifold studs.
While waiting for new pipe to come, after ordering it, I took the old system off Dragon. I used the one good piece of pipe, and the collector, from Dragon and made this.
Another look at the down pipe, and collector.
This is how it fits between the torsion bar, and transmission.
Torsion bar side.
After welding the collector, and down pipe together, I had to "adjust" the fit a little.
While I was "adjusting" the fit, this showed up.
I am pointing to the area UNDER the transmission crossmember where the exhaust pipe goes.
Right after the pipe goes under there, it crosses over to the right side of the truck, and goes OVER the center support bearing crossmember, about where the "adjusting" tool is balanced.
First, I bolted the two inch down pipe I made on Wednesday, on the engine.
Then, I took one of the flanges, welded it to the end of one of the 4 foot pieces of straight pipe, and slid that over the manifold down pipe, and made a mark where I needed to cut the straight pipe to put in the elbow.
I was just cutting, and trying, and guessing where pieces of pipes would fit. After a lot of that, I ended up with enough exhaust pipe to hang over the bearing cross member, and meet the down pipe. I attached the exhaust pipe to the down pipe with a pair of flanges.
Here is where the pipe goes under the transmission cross member.
and this is the pipe going over the bearing crossmember, with a supporting clamp already installed.
A close view of the pipe clamp.
And finally, this is where I ended up. with the pipe hanging under the bed, where the muffler will be located. I had used the two 45 degree bends, that came with the pipe I ordered, and one of the 4 foot sections. I still had two 90 degree bends left.
When I got that far, I did not have a muffler, yet. I used the "universal muffler search" on this page,
and plugged in the parameters for the muffler. A quick note, exhaust pipe is measured by the OUTSIDE diameter. Mufflers are measured usually by the inlet, and outlet INSIDE diameter. This is so the exhaust pipe will go into the muffler.
the "Universal muffler search" returned over 20 different mufflers. I eliminated the few that were too long, and called a local auto parts store, and gave then the list of possible mufflers. They called back, with one that I could get the next morning. It was a Walker 17900.
Once I had the muffler, I could then hold it up under Dragon to see how it would fit. Nothing too scientific, other than "that looks about right" The muffler was placed here.
To get it there, I had to shorten the end of the pipe sticking out from under the cab, I also cut part of one of the 90 degree bends, to make the muffler point up close to the mount in the above picture.
This is the bend in the front pipe, to point the muffler up where I wanted it to go.
Then I used another section of what was left from the 90 degree bend to turn the tailpipe down after the rear axle.
and I had a small section of the 90 bend left to make this bend.
Even though some of the above pictures were with the system on Ratsun, the entire system was built on Dragon.
I took this picture Thursday morning. I still had not yet done any work on removing the old exhaust system from Ratsun.
Thursday after noon, about 4:00 PM, I ran Ratsun up on ramps, on the front, and jacked the rear up, and put stands under the rear axle. I unbolted the pipe hangers from the frame of Ratsun, then I used a 3 inch cutoff disk to cut the tail pipe off the muffler, the front pipe off the muffler, and made a cut where the front pipe bends, by the transmission. I then unbolted the down pipe from the exhaust manifold.
With the old system out, I bolted the down pipe to the manifold. Then I slid the front pipe over the drive shaft center bearing crossmember, and bolted the flanges on the down pipe to the front pipe. Next, I slid the muffler on the front pipe, and then put the bend of the tail pipe over the rear axle, and into the muffler.
I then twisted the muffler around to move the pipes where I wanted them, and bolted it up with the hangers. And Ratsun was back on the ground, around 5:30.
I have a small leak, in the bottom of the bend right in front of the muffler, and I had to tighten up the clamp on the front of the muffler.
And this is what I have left. I need three 15 degree bends, and a muffler to complete the system for Dragon.
Posted 20 January 2015 - 01:50 AM
Great work Daniel.
Up the irons!!!!!
71 521 red beater thread
72 521 blue thread
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80 210 thread
Posted 20 January 2015 - 06:51 AM
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Whenever I think that I'm out of my mind for putting this much time and money into an old Datsun, all I have to do is look some of your threads to know that I'm not nearly as whack as you are.
You're going to skin a few knuckles, stand up too fast and bump your head, hunt around the floor for the nuts and bolts you dropped, invent a few new cuss words and when you're finished you'll say "That wasn't so hard after all!"
Posted 20 January 2015 - 06:54 AM
Thanks for the encouragement!
I recently got Dragon able to move itself again, and since I used it as a model to build Ratsun's exhaust system, I took the rotted exhaust system off Dragon. I started Dragon with just a two inch straight pipe. Maybe because an old, it was really annoying.
Before I move Dragon too many times, it will get an exhaust system fabricated for it.
Dragon is this truck.
Posted 20 January 2015 - 09:49 AM
I am not quite there yet. For some reason, when I fabbed the system on Dragon, the pipe from the manifold down pipe back under the driver, and crossing over to the other side of the truck just pretty much fit into place, on Dragon, and then pretty much bolted into Ratsun.
When I tried to duplicate the same system on Dragon, it did not fit as nice.
Dragon was not a high priority at that time, so that part of Dragon project is shelved.
But Dragon is coming closer to a priority now. Once I figure out the reason for things not fitting the second time, then I can maybe start building 521 exhaust parts for other people.
Posted 10 February 2015 - 07:35 AM
Posted 10 February 2015 - 10:26 AM
You do nice work.. I'd love to do this on my dime.. but I'll probably just take it to a shop.. or just hack it together for now. Not decided yet.
Posted 10 February 2015 - 11:02 AM
I had a few reasons for doing this myself. Biggest reason, i have at least three 521 trucks that need exhaust systems.
I had the advantage of having one truck up in the air, that I could fabricate an exhaust system for, and then move it to my daily driver.
If I was doing only one system, and did not have a second truck to mock up the system on, I probably would have just paid to have it done.
The tubing I used is 16 gauge. It is pretty easy to weld. It can be cut fairly easily with a cut off disk, and a grinder. And abrasive chop saw would also work, or even a hack saw, if you are desperate.
I ordered tubing from these guys:
Posted 24 February 2015 - 11:25 PM
I have been working on Dragon's exhaust system.
In this picture, I was getting ready to tack weld the flange on the down pipe, coming off the engine. When doing any electrical welding on your car, or truck, try to attach the ground lead as close as possible to where you are welding. Do not just put a ground clamp on the bumper, and expect a good ground to anything else. Also, the high currents used in welding can damage what would be an OK ground between different parts of the car that normally only carry ground current for parking lights, for example.
This pips was giving me some problems fitting in the right place, before. It was built using 45 degree bends, and I did that with the first exhaust system I made, and it fit. I looked at a stock exhaust system on Dragon Two, and noticed the pipe had sharper bends in it. I got a few more bends, and made this pipe with two 75 degree bends, and it fits good.
This is a stock pipe mounting clamp. I added some extra metal, to fit the 2" diameter pipe. The bolts are loose, because I am sliding the pipe in and out of it, for measuring, tack welding, test fitting, removing again, and final welding.
I got a larger muffler for Dragon than I put on Ratsun. The muffler was just slid on the pipe, this is not it's final location. No tail pipe, yet.
Here is the down pipe, front pipe, and muffler on a cluttered bench.
Another picture of exhaust pipe, and muffler on the bench.
Posted 06 March 2015 - 10:45 PM
I finished "mostly" the exhaust system install on Dragon. I still need to put one clamp on the front of the muffler.
This is the front exhaust pipe bolted to the engine down pipe, with a flange.
This is the forward pipe "hanger". I took the stock 521 pipe holder, cut the legs on it, added some more length to it, so it would fit a 2" OD pipe, and used it.
This is where the end of the front pipe is under the rear of the cab.
The pipe need a slight turn up to fit the muffler. The front of the muffler hangs on this pipe, and the back end of the muffler goes here.
This is the start of the bend for the front of the muffler.
It just slides into the muffler.
Here I held the muffler with the piece of pipe in it, so I could see how much I needed to trim it to put the muffler at the right angle to fit.
This is the short piece of pipe that was slipped into the muffler, welded to the front pipe. Because of the flange, at the front of this pipe, I can easily take it out of the truck, weld on it, and put it back in the truck.
This is how the back of the muffler was hung off the middle pipe mount. The muffler got shifted about 2 inches forward after this test fit.
With the muffler in place, or close to where it will end up, I started working on the tail pipe. This pipe goes over the rear axle, and then bends down, and then back straight to exit below the bumper.
Here I am holding the second bend that goes to the rear of the truck.
Those pieces got welded together, and a straight piece of pipe was added. This is the front of the tailpipe.
This is the rear part of the tailpipe.
And the welded tailpipe test fitted on the truck.
This is the final location of the muffler.
Another picture of the muffler location.
This is a close view of the rear pipe hanger.
This view, is the aft end of the tail pipe.
This is where the tail pipe exits under the bumper.
Posted 17 December 2017 - 07:19 AM
I have all my pictures and have put PB behind me. If I went and tried to replace them all it would take 10 years. Many are on google images and those can be copied by others.