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Frame Off Restoration - Step 3 - Dealing with the Exhaust System

Introduction

Every car has some form of exhaust system. Depending on the age of the vehicle the primary differences you will see relate to newer cars, especially from the seventies onwards. This is due to governmental regulations about emissions of vehicles. So, while your fifties car may have simply a long exhaust pipe with a muffler somewhere along it's path, a newer car could also have a catalytic converter and oxygen sensors (O2 Sensors). For the scope of this article the exhaust system is defined as the region beginning at the end of the exhaust manifold to the point where the exhaust pipe exits the back of the vehicle.

Now, more often than not, I've found that I end up pulling the exhaust system that's on the car and recycling it. Then I wind up installing a brand new system. I recommend you start with that in mind before you go tearing into everything.

Removal

Almost every single exhaust system is installed the same way. The exhaust is either bolted or welded to the exhaust manifold and then routed out the back of the vehicle. As you go back on the car either the exhaust will have hangers welded to it, or there will be rubber and steel clamping assemblies that connect the pipe to the car. The rubber aspect is important as it allows the exhaust pipe to move and flex. Without it you would wind up with an exhaust pipe that eventually cracks due to the stress of it attempting to vibrate but held still.

Take a look at your exhaust system. It may be a number of segments bolted together, or one long contiguous piece. To remove it, first unbolt it from the exhaust manifold. There also should be a gasket at the mating surface of the two pipes. On the off chance that it was welded to the exhaust manifold you have a decision to make. Are you going to re-use the assembly or replace it? If you are going to reuse the assembly you'll have to additionally remove the exhaust manifold. Now, a caveat on this. If the pipe was welded in place while the manifold was on the engine, then you may not be ablt to remove everything as a single unit because of clearance issues. So, carefully determine if you can remove the entire unit as is. If not, then you will be forced to cut it off. If cutting is the necessary solution, cut through the exhaust pipe, not the exhaust manifold.

Now that the exhaust pipe has been disconnected from the manifold you should be able to work your way towards the back of the car disconnecting the exhaust pipe hangers. Once the hangers are off, then it's simply a matter of sliding the exhaust manifold out from under the car. Now, in some cases (like my Jensen Healey) the exhaust pipe consists of a routed assembly that was welded together as it was put on the car, and because of this there's no way to easily drop it out because of the way the pipes were routed. This is another instance where, if it's not been bolted together in multiple segments, you will have to cut through the exhaust to remove it.

The final step is to go back through and remove as much of the exhaust hanger assemblies as are removable from the car. In many cases the part of the hanger that's attached to the body is welded in place. So only remove what is removeable. Keep each hanger assembly in a separate pile for now.

Disassembly and Restoration

So, restoration may be a bit of a misnomer here. As you're more likely to replace than restore. What you really need to do at this point is decide what tye of exhaust you want to put on the car depending on the restoration type. In the case of a concours restoration it's an easy answer, the original stock set-up. However, if you're building a resto-mod or a hot rod you'll want to evaluate how much airflow the engine will need and what sort of exhaust note (sound) you will want the car to have. In addition, should you change the exhaust system you will need to determine how it will fit on the car. In some cases, going with a larger diameter exhaust means that you will have to reroute where it goes underneath the vehicle.

So, if you're doing a concours restoration this piece is simple. Add the exhaust parts to your parts list and order them. Don't forget to order replacement gaskets and rubber hangers as well. If there are any metal clamps, nuts, bolts, etc. you'll need to toss them in the sandblaster, clean them up, and then paint them. This is another area where I recommend a coat of POR-15 followed by some Chassis coat. When you evaluate the nuts and bolts for wear and ust damage determine if they can be reused or need to be replaced. Generally speaking, if you can find matching bolts, nuts, and washers new, then replace. If you cannot, and the originals are salvageable what I like to do is use a wire wheel on my dremel tool to clean them up, and then use a rust preventative spray paint to treat them. The only part that requires significant care is to not fill the threads with too much paint.

If you're not going to replace it with a stock exhaust system I recommend holding off on the exhaust until you finish the engine rebuild. The reason for this is that depending on how extremity of the engine modification will define the necessary airflow through the system and thus the diameter and efficiency of the exhaust system. This is an area where finding peers hat have done the same or similar engine modifications will be very useful because they will have had to solve this problem already.

Reassembly

This is one of the few cases where most of the reassembly will be performed at the end of the restoration. The reason for this is that the exhaust system as a complete unit takes up a lot of space and you don't get a major time savings for doing it in advance. What I normally do is actually wait until the end project to order any new exhaust pipes. I do, however, immediately reassemble the exhaust hangers and order the rubber parts that are involved in the assembl. Then, bag each hanger assembly separately, note where it went on the vehicle and store it away in one of the 12 gallon containers. Don't forget to label the exterior of the container so that you know what it contains!

On to Step 4: Fuel System

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Contents copyright 2008, 2009 - Jody F. Kerr

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