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New C4 Exhaust System - More Bark With Your Bite, Part 1
New C4 Exhaust System Adds Power And PRRRRR
Sep 1, 2008
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New C4 Exhaust System - More Bark With Your Bite, Part 1
Here's our header system from Stainless Works, complete with A.I.R. plumbing, an EGR port, and a bung for the O2 sensor, along with nifty band-type clamps that are attractive, effective, and don't crimp the pipes being clamped, making any future disassembly a hassle-free experience.
Removal of the rear half of the original exhaust system is as simple as removing three bolts at the flange of the catalytic converter and two hangers at the rear of the mufflers. It all comes down in one piece, which we'll keep for the lucky guy who will end up restoring this car twenty or thirty years from now. Before removing the cat converter, we marked the underside of the car at the rear edge of the catalytic converter flange. This would allow us to be sure the new system was in the proper fore-and-aft position to ensure proper alignment and positioning.
The air feed tube to the catalytic converter is a multipiece affair. We used a cut-off wheel to surgically remove the clamp, being careful not to nick the tubing since we knew we'd be re-using it with the new system.
Here's the complete original exhaust system in surprisingly good condition considering it's twenty years old. the car has always been garaged and has just 35,000 miles on it (some a quarter-mile at a time, of course), which has helped preserve this system that could be re-used if desired.
This clamp secures the metal A.I.R. tube to the front pipe to prevent noise, vibration, and possible metal fatigue.
This bracket is essential for supporting the alternator. Word on the street is that leaving it off will result in a broken mounting ear on the front of the alternator. As you'll see later, we had to fabricate a new bracket since the original would not clear the header tube.
The left-side exhaust manifold lifted out easily without the need to remove the alternator, just the bracket mentioned previously. We were even able to leave the spark plug wires installed while removing the left-side manifold, but we did have to remove them and the spark plugs, on both sides of the engine, in order to position the new headers.
The high-performance catalytic converter from Random Technologies is more than just another replacement converter. In our discussions with the folks at Random, we were impressed with the depth of their knowledge in overall engine management and how it must be carefully integrated with various performance parts so everything works in harmony.
Since our headers and mufflers are so pretty, we decided to send the extension and "Y" pipes to Classic Coatings for their chrome-like ceramic coating. The finish was spectacular and will inspire us to place mirrors under the car at shows to display the gorgeous finish on the entire exhaust system. We did notice some small balls of material in some of the inner nooks and crannies of the pipes, which seem to be leftover from the plating process. While they appeared harmless, we did take the time to remove them using a dentist's pick.
Since our '87 is equipped with aluminum cylinder heads, we cleaned off the old gasket material by pulling rather than pushing on a razor blade in order to prevent gouging the metal. The gasket surface needs to be perfectly clean to prevent leaks. We cleaned the last of the gasket material off with an abrasive pad, but we left the spark plugs in and also plugged the exhaust ports in order to keep abrasive particles out of the engine.
In anticipation of a snug fit and to ensure the entire job was done with quality parts, we picked up a set of ARP header bolts from our local speed shop.
The flange on the Random Technologies cat converter has extra bolt holes to allow it to fit multiple applications. It also includes ports on both sides for connection of the A.I.R. tube on different applications. this is no "will-fit" universal part-it's designed for alternative mountings and was a simple and direct bolt-in.
Here's the Corsa cat-back system that was recommended by Mid America Motorworks. It's made to mount to the factory hangers, making installation a snap after the headers are in place.
Installing the left-side header wasn't too difficult. There was adequate room to lift it up into place from below. We tried dropping it down from above, but there was simply not enough room to snake it into place.
The new headers didn't come with gaskets, so we bought a set locally. Note that the bolt holes on the front and back of the gasket are not full circles, but rather are slotted. This allows us to install the header with the end bolts first to hold it in place, and then slide the gasket down into position before installing the remaining bolts.
Here you can see how easily the new gasket slides into place with the two end bolts holding the header in place. This is far easier than struggling with trying to start the bolts while juggling the header and the gasket at the same time.
As it turns out, all four of these brackets (two on each side) interfered with the header flange.
Fortunately, we didn't have to cut any material off these brackets. we only needed to bend each tang 90 degrees to prevent interference with the header flange.
The original alternator rear support bracket bolted to the rear bolt of the front tube on the driver-side exhaust manifold. The new header tube does not leave clearance for the stock bracket, so we decided to make a new bracket and mount it to the next bolt back.
We used the original long shouldered stud and made a "stand-off" tube to move the hex head out where we'd be able to attach a bracket without contacting the header tube.
Even with the stand-off tube, the fit was so snug that we had to grind off the integral washer until it was even with the hex.
As long as we were changing out the whole exhaust system, we chose to install a new Bosch oxygen sensor. While these sensors are usually thought of as being expensive, ours was only $21!
It's no surprise that twenty-year-old plastic that's been heat-cycled a zillion times is brittle. The lock tab broke off this O2 sensor wire connector when we disassembled it, so we used a plastic tie to hold the connection together to prevent future problems.
You can see that the hose from the oil filter is just too close to the header tube on the driver side. We ended up using several 90-degree adapters and hose clamps to position the hose away from the header tube until we decide on a more professional-looking solution.
In the course of our work, we found the speedometer sensor at the rear of the transmission was leaking. With the exhaust system removed, this was the logical time to repair this simple problem.
Just one bolt holds the clamp on the speedo sensor. With the clamp out of the way, the sensor pulls right out.
The fix was as simple as replacing the O-ring on the sensor. Three cautions here: lube the new O-ring so it slides into the transmission more easily; be careful not to nick the O-ring; and be careful when removing the unit so the speedometer gear does not fall off inside the transmission.
We found we had to bend this lower heat shield on the passenger side in order to keep it from vibrating against the header.
This is the functional, but not very pretty, temporary solution to the interference problem with the hose on the driver side that carries coolant from the engine block to the oil cooler, which is part of the oil filter adapter. A more sanitary solution is in the works.
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