The Fifth came with a 2.2:1...
The Fifth came with a 2.2:1 geared 7 1/4-inch rear, too weak and with the wrong gears for the modified car. An ex-police Diplomat had the 2.71:1 8 1/4-inch rear I wanted, plus the stout police package rear suspension. The entire rear and suspension was dropped out as a unit by just backing out 12 bolts. The toughest part was unhooking the parking brake cables.
Cold Air Induction
Collecting dust in my garage was an old asymmetrical dual-snorkel air cleaner off a mid '70s 440 C-Body. It was one of those wrecking-yard finds that was snagged for no particular reason other than it was unusual, kind of cool, and cheap. The Fifth originally had a small two-barrel-sized air cleaner with a single cold-air induction snorkel feeding from a duct behind the battery. The dual-snorkel piece had a single cold-air primary snorkel in the same general orientation as the stocker, but also had a secondary snorkel feeding from under the hood that tipped into action at wide open throttle.
Perching the odd dual snorkel on top of the 360's ThermoQuad carb, it fit like a glove, lining up perfectly towards the cold-air duct on the primary snorkel. The secondary snorkel cleared the A/C and heater hoses to the rear, and the oil filler to the front. It was even notched to clear the late model axial A/C compressor, a perfect fit.
There was no doubt the 360 would need more than a single snorkel to breathe, and this unit had the stock looks that would pass a casual visual smog equipment inspection. It seemed odd, though, that the secondary snorkel would draw hot underhood air. To give the 360 cold air from both snorkels, a hole was cut into the right side inner fender apron, and a duct was made from a cut-down air duct culled from another junkyard M-Body. Installed, it looks like it could have been stock.
To clear the exhaust, the...
To clear the exhaust, the sway bar had to go in first. All M-Body frames are pre-drilled for the bar.
Exhaust Upgrade
With the engine in and the induction side done, the exhaust system was next on the list. The stock 318 system is a tortured example of inefficiency, starting with two mini-catalysts bolted right to the restricted manifold exits. From there, the pipes neck out at a strange angle from the primary cats to a single 2-inch main cat, through a muffler, then a resonator, and out the back. Yikes. To the letter of the law, this is the smog legal system, but this machine wasn't going together to the fine points of the code. Making the visual grade in a smog check might just mean that the inspector pokes his head under the car, spies a cat, and moves on. Headers were out on two counts: making the inspection, and my wife's single request that the car wouldn't be loud.
M-Bodies always had a single tail pipe from the factory because of the offset gas tank which leaves exhaust clearance for the tailpipe on only one side. There was a factory "dual exhaust" system available on earlier cars, which used separate pipes off each manifold feeding into two cats, followed by dual mufflers, but after the mufflers the system merged in front of the rear axle out a single resonator and tailpipe. A true dual system can be installed by moving over the gas tank, but that wasn't the plan.
The Fifth would need a cat, but I decided to cut down to just a single cat, a massive high-flow single 3-inch unit. For manifolds, the skinny 318 units were tossed for a set of factory 360 pieces, with the heat riser valve cut out. From there the system feeds into 2 1/4-inch pipes merging to a 3-inch pipe to join the large cat. From the cat back, a single 3-inch pipe carries the exhaust through a short Walker DynoMax turbo muffler and out the back. The system showed minimal back pressure, but is kind of loud. (Sorry, dear.)
With the rear in, the rear...
With the rear in, the rear suspension was finished with a set of KYB gas shocks from PST.
Here's the important hardware...
Here's the important hardware up front, a pair of special police-only transverse torsion bars and the huge cop sway bar. The critical part is the pivot bushing at the bend-it has to be in good shape.
The cop front suspension drastically...
The cop front suspension drastically alters the character of the car. It's not harsh, but the improvement in handling is unreal. As with the rear set of PST's KYB gas shocks finished off the front.