1965 Plymouth Belvedere - Turbo Action!

The pair of Majestic customs were positioned into the inner fenders on opposite sides of the car, taking air into the compressors via filters mounted directly to the compressor inlet from the front of the wheelwell. A set of beat-up Hooker headers were butchered and rewelded to funnel exhaust pressure back to the turbines, which then routed it out to the mufflers under the car. The boost is controlled by a pair of Tial wastegates. The diaphragm inside the wastegate is fed boost pressure. When the pressure builds high enough to overcome the spring pressure on the diaphragm, it pushes open a valve in the header. This allows the exhaust gases to bypass the turbine and to maintain the desired pressure. Without them, the turbos would probably boost the engine into oblivion. Once the compressor side is finished pressurizing the fresh air as a result, the charge funnels to a reverse Y-pipe mounted in front of the radiator, then the single tube runs up to the K&N Filtercharger bonnet atop the carburetor. A pair of pressure bypass, or blow-off, valves on this inlet pipe make sure rampant boost doesn't cause damage when the throttle is closed. These came from junkyard 2.2 turbo cars, cost a couple of bucks at the boneyard, and are mounted about a foot before the carb inlet facing downward; Kevin says they'll blow your hat off if they open at full boost. An oxygen sensor from an '87 Gran Fury was also put to use to monitor the process.

Next was the carburetor problem. Metering fuel/air for forced induction into the carb throat can be a little trickier than having a blower draw air from below the carb. Kevin tried several different carbs, with a modified 650 Holley being the best so far. The fuel metering system needs to react quickly to changes in air pressure, and a vacuum line is routed directly to a diaphragm-type Mallory fuel regulator on the firewall, increasing fuel pressure as the boost increases. Kevin says he is still experimenting to find the best solution in this area and fuel injection would be a much easier way to run turbos in many regards.

A few additional modifications include stainless oil lines coming from the two oil-sending unit holes in the block that now route engine oil into the turbos, returning it to the oil pan when finished. Without lubrication at high rpm, these units are capable of explosive problems. The air plumbing for both the compressor side (up to the carb) and the turbine side (exhaust gases from the headers, through the turbine, and out to the mufflers) is bulky, but was installed in a few days by a local muffler shop. Auto Meter gauges allow Kevin to watch air/fuel ratios, oil pressure, and other vital signs. On the dyno, even this early in the experiment, the engine made 359 horses at the rear tires with only 6 pounds of boost.

This is Kevin's first project involving turbochargers; he had a turbo-equipped Shelby Charger a decade ago, but little of that science will platform directly to the big-inch V8 environment. The photos show this car is no trailer rig; still in progress, it doesn't even have the replacement hump for the new four-speed trans welded to the tunnel yet. However, Kevin gets an A+ for ingenuity; he invested less than $6,000 in the entire project, and the engine program set him back a mere $3,500, including a bucks-down rebuild on the 440 mill.

The engine is a .030-over '68 block with 8.7:1 pistons installed. A set of later -452 heads were used, including a custom-ground Comp Cams bumpstick with .488 lift and 10 degrees of overlap. For timing accuracy, a Pete Jackson geardrive was added. A pair of twin electric fans round out the package. Kevin, who has a '92 Cummins D250 pickup that makes 527 lbs.-ft. of torque at the rear tires, plans to add an intercooler to the '65 as soon as possible. This is an air-to-air type unit, which routes the incoming charge from the compressor into the carburetor and produces power by reducing the charge air temperature.