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New C4 Exhaust System - More Bark With Your Bite, Part 2 - Tech
Our Project '87 Gets A New Set Of Vocal Cords
Sep 29, 2008
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New C4 Exhaust System - More Bark With Your Bite, Part 2 - Tech
Picking up where we left off last month, we removed the heat shield on the passenger side to allow for installation of the right-side header. This shield keeps exhaust heat away from fuel lines and filters. It required a little cutting after the header was installed in order to allow a sufficient air gap between the header and the shield.
Two of the three manifold nuts were so heavily rusted that the studs broke off, even though we had sprayed them liberally with penetrant. if we were going to re-use these manifolds, we would have replaced the studs and also used extra-long brass nuts made specifically for use on exhaust manifold studs.
We marked the underside of the car at the rear edge of the catalytic converter flange. This allowed us to be sure the new system was in the proper fore-and-aft position to ensure proper alignment and positioning. Here, barely visible, is the hose clamp that holds the A.I.R. tube in place on the passenger side as seen from below. We're not sure when this clamp might have been installed when the car was built, but there's surely no way to get any kind of screwdriver on it or even a 1/4-inch drive socket, so we used a small box wrench to loosen it.
On the driver side is a coolant temperature sensor located between the two front spark plugs. this must be disconnected very carefully since this-like all the other plastic connectors in the engine compartment-have grown brittle with age and break easily. Happily, ours did not, but we were very gentle with it. The left-side exhaust manifold lifted out easily without the need to remove the alternator, just the rear support bracket. 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.
No, we're not trying out for the Olympic pole-vaulting competition; this was the only way we were able to remove the A.I.R. tube that runs back to the catalytic converter. Reinstallation was similarly awkward.
As shown in the previous photo, we had to disconnect the ESC knock sensor in order to gain clearance to put the right-side header up into place.
We were surprised to find that the right-side header was such a snug fit that we had to remove the torque converter inspection cover and just about everything else in sight to find enough room to squeeze the header up into place. Yes, the starter had to come out as well. Since we knew this was going to be a pretty ambitious project, we had disconnected the battery at the beginning of the job so sparks wouldn't fly when we were working around electrical connections.
Trial and error taught us that we would not be able to install the upper bolt of the starter support bracket once the header was in place. we left it in place, but loose, so we could pivot the bracket as needed when sliding the header into place.
Here's something else we didn't expect. There's no way the right-side header would go in without removing the engine's oil dipstick tube. We tried a mechanic's trick of using hose clamps, a piece of coat hanger, and a slide hammer with gripping pliers to try to extract the tube from above without damaging it, but to no avail. After several tries, we ended up using locking pliers and a hammer, knowing we'd ruin the tube in the process. We ordered up a new dipstick tube from our local Chevy dealer for $37.
The right-side exhaust manifold is just about ready to come out. Notice the routing of the original engine oil dipstick tube. That will end up being well in the way of the new header.
The wiring harness clip must be removed before unbolting the right-side frame reinforcement bracket. The bracket had to come out in order to gain additional clearance.
We even had to remove this small wiring harness bracket that lives above where the starter used to be. Note the band-aid that covers just one of the many cuts and scratches this job produced.
We found that the fuel filter heat shield touched the header tube on the right side, so we elected to modify the shield slightly.
Likewise, it was necessary to remove this coolant temperature sensor from the right-side cylinder head. Many of the interference points were very subtle and could only be identified by trial and error.
We probably attempted this twenty times, each time finding some other part that had to be moved or removed to allow the header to fit.
This was, by far, the trickiest part of the job-getting the right-side header into position.
The mark at the upper left shows how much we had to trim the heat shield in order to provide adequate clearance with the header.
Here's how we cut and spliced the A.I.R. tube so it would fit around the header. We used special high-temp hose to make the installation easier, safer, and more reliable.
Finally! With both headers bolted firmly into place, we could move on to the part that is fast, fun, and easy. Here, we're installing the front Y-pipe to the headers.
Supplied with our Random Technologies converter is a machined plug to block off whichever A.I.R. input tube will not be used. It's precisely made and fits snugly with a few taps of a hammer. an elbow is also supplied, along with the previously mentioned high-temp hose, to facilitate installation.installation.
The original front Y-pipe ran straight down the middle of the tunnel. Our new headers and Y-pipe are slightly offset to the left, so we added a few washers at the bracket mounting point to align the bracket to the pipe.
You'll recall that when we started this job, we had marked the frame of the car to identify the rearmost point of the catalytic converter outlet pipe. Since we were working with parts from multiple suppliers, we wanted to ensure a proper fit; we found that we needed to trim about a half-inch off the front Y-pipe to achieve alignment with our mark.
This is the original design metal support strap as used with the original mufflers. We removed these from both sides since our new Corsa mufflers are already fitted with "tongues" that slide through the mounts in place of these brackets.
The 90-degree elbow supplied with the new converter allowed for a simple connection using the high-temp hose that was also supplied.
This view from below shows how we spliced in a piece of the high-temp hose from Mid America Motorworks in order to allow us to properly position the A.I.R tube.
With the rear Y-pipe in position, we could now install the extension pipes that go back to the new Corsa mufflers. Note the gorgeous finish on these pipes, courtesy of Classic Coatings.
This is the tool we had to make in order to tighten the front and rear spark plugs on the passenger side. The header tube passes so close to these plugs that you can't fit a deep-well socket over the plug, and the plug is recessed so far into the head that you can't fit a box or open-end wrench on it either.
We really like the band-type clamps from Stainless Works. They're beefy, tighten superbly, and secure well. We especially like the fact that they don't crimp the pipes, which can make for a very difficult disassembly down the road.
We used a tubing cutter to shorten the original A.I.R. tube after the cat converter was bolted firmly in place.
We sacrificed a 5/8-inch box wrench, cutting the handle off short. We also sliced off half of a 5/8-inch, 12-point socket, indexed them so the points aligned, and welded the socket to the shortened box wrench.
The finished job is as pretty as it was difficult. After all the tweaking, the installation looks great, fits well, and doesn't have a single leak or rattle.
Note that the band-type clamps actually conform to the size and shape of the smaller diameter pipe to ensure a positive seal between the two different diameter pipes. We were impressed with this clamping capability.
Bolted up, the Corsa mufflers and pipes are a perfect fit. The entire new system snugs up to the underside of the car so no noticeable ground clearance is lost.
The chrome exhaust tips exit right where the factory tips did. They sit just far enough back to tell folks we have a custom system without being too obvious. The sound is just right, too.
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