Obviously, the first thing we needed to do was remove the existing exhaust system. We applied penetrating oil to all of the nuts and bolts to make sure we could loosen everything without the use of torches. We started by loosening the intermediate pipe.
We then used a Sawzall to make it easier for us to remove the exhaust from here back.
We carefully and simply pulled the existing exhaust out the back, leaving only the intermediate pipe in place. As you can see, our 1974 had Flowmaster 3-chamber mufflers on it, so the car already had a good sound. Would the side pipes improve things in the sound department? By then it was too late. There was no turning back.
Chris then moved on to the intermediate pipes and quickly removed them. These components had been married for over 24 years, so it took some extra work to loosen them. We used a torch to help extract the right-side exhaust inlet pipe. Don’t use an impact wrench in this situation; you may do more damage in the process. The use of the torch is one reason this job is pretty difficult to do in your home garage, not to mention that you’ll need a lift.
With the exhaust inlet pipes off the car, we could get to the exhaust manifolds. Any bolts that could be reached easily from the bottom were loosened at this time. Also, remove the spark plugs and plug wires.
Once everything was loosened from the bottom, we set the car on the ground and disconnected the battery. The need to remove the alternator made it necessary to disconnect the battery while we installed the headers. Once all of the wiring was disconnected, we could remove the alternator.
With the alternator out of the way, we loosened the remaining left-side exhaust-manifold bolts and removed the factory exhaust manifold.
Here’s what was left after the exhaust manifold was removed. Then we could move to the other side and get it ready for the headers.
Here Chris loosened the aftermarket plug-wire looms that were present on our 1974. They were attached using the valve cover bolts. We deep-sixed these wires, located a set of correct-length plug wires, and reinstalled them in the right location.
The A/C compressor needed to be pulled out of the way for our header install. You don’t have to disconnect the compressor, but you do have to get it out of the way. One of the compressor brackets attaches, along with the exhaust manifold, on this side. With this bracket removed we let the compressor rest on the inner fenderwell.
Once the compressor was out of the way, we removed the compressor bracket and the remaining exhaust-manifold bolts, and then removed the exhaust manifold.
Here’s our exhaust system with all of our components removed. We discarded the ugly and non-mandrel-bent pipe, but saved the vital parts just in case we wanted to return the car to rear-exit exhaust some day. (Yeah, right.)
Before we installed our headers, we cleaned up the bolt holes using a 3/8-inch, -16 tap. This made it a lot easier to thread the new bolts in, not to mention tighten them properly.
Here are the middle exhaust ports. Notice we cleaned up the surface area and were ready to start installing our new headers. A clean surface is essential for proper gasket sealing.
Then we returned to the underside to install the headers. There’s no way to install these from the top, so don’t even try. While we were down here, we went ahead and started a couple of bolts and moved on to the other side. (From the looks of the oil pan, this 1974 is crying for a ZZ4 swap. Anyone out there interested in a ZZ4 project?--Ed.)
Once we got a couple of bolts in each side, we could again move to the top side and install the rest of the bolts. We’re using Stage 8 fasteners for our installation. They’re not necessary, but they do keep exhaust bolts from wriggling loose after a period of time and causing an exhaust leak. Man, you gotta love chrome.
Here’s our completed left side. Notice the way the Stage 8 fasteners work. You install the bolt, then a wedge keeps the bolt from wriggling loose, and then a clip is used to hold the wedge in place. You can also see that our new plug wires are heading in the right direction.
Here’s our A/C-compressor bracket that we removed when we began taking out the exhaust manifolds. Notice how much it had to be modified in order to fit the new headers. This bracket attaches using the first and third (from the front) header mounting bolts on the right bank. The increased primary size of the headers necessitated modifying this bracket.
Here’s a better look at how the A/C compressor bracket attaches to the engine. Make sure the bracket is straight before you reinstall the compressor.
In this shot you can see the spacers we used to reinstall the A/C-compressor bracket.
We had to notch the lower fender ever so slightly to make sure the headers wouldn’t rub on the body and drive us crazy going down the road. Our 1974 recently went through a blown-tire episode at the right front, and the fender had to be repaired. We think that may have something to do with us having to notch the fender; either that, or we have some body-mount issues to be settled on the car.
When the headers are fully mounted, you can slide the pipes on and tighten them using the supplied nut and bolt. We didn’t totally go off the deep end when we decided to put side pipes on our 1974--we did get the reverse-flow slip-in mufflers to prevent us from going deaf prematurely. (Huh, what’d you say?)
We were able to retain the side mouldings, even though it was a tricky operation to get them back on the car. You must remove the mouldings before you can install the pipes properly, and then carefully slide the side mouldings back in place once the pipes are installed. It’s tricky, but take your time and you’ll get it done.