Fueling Sixes - Jeep 258 Turbo Engine Kit

The first hour or two of the install is spent removing the carb, the old intake, and the exhaust manifold along with everything attached to them. This Jeep had an AIR pump, which complicates things a little but can be made to work with the new system. It's helpful to clean the engine at a coin-op car wash before beginning the swap, and to soak the manifold and exhaust bolts with WD-40 or another penetrating oil. The intake and exhaust manifolds are bolted together and are easiest to take out as a unit.

On the other side of the engine, the distributor must be removed. Mark the location of the rotor so you can install the new distributor in roughly the same position. If you're having to update to a later distributor, your original plug wires will still fit.

When your engine looks like this, you're nearly ready to start adding new components. Inspect the freeze plugs in the block. If they're hashed, you can easily change them now that the manifolds are removed. This is also a good time to consider changing radiator and heater hoses.

This Jeep is a 1977, a model that used a Prestolite ignition. The Turbo City computer will now control the timing curve, so a magnetic-pickup distributor (right) from an 1981-or-later 258 is needed. You'll need to gut the distributor of its mechanical and vacuum advance mechanism.

To disable the mechanical advance, you must remove the distributor shaft and weld the weights in place. The shaft can be slid out of the housing after the roll pin retaining the timing gear is removed. If you're not comfortable doing this, most automotive repair shops can do it.

The Turbo City kit is one of the few TBI retrofit systems that can legitimately claim a power gain in addition to the benefits of fuel injection. The gain comes from the Offenhauser intake manifold included in the kit. The plenum is much larger, as are the runners. Even on our well-worn engine we noticed a big difference in power, especially at part-throttle.

If you use the stock exhaust manifold, it must be bolted to the bottom of the new intake manifold. You may use a header with this system

This is the hardest part: swinging the intake and exhaust manifolds over the fender, lining them up with the dowel pins, and getting all the bolts in. The AIR line made this even more challenging on this Jeep.

The throttle body is a two-injector GM unit that Turbo City reconditioned. Which accelerator cable bracket you need depends on the year of your Jeep. In this case, the original cable connected with an S-10 bracket, leaving a loop in the cable.

Fuel injection requires steady fuel pressure in order to function properly. The Turbo City system uses relatively low pressure (about 9-13 psi), and an electric, inline fuel pump gets the job done. The pump is spliced into the stock 5/16-inch fuel line and must be mounted lower than the fuel tank to make priming the pump easier.

A block-off plate is installed where the factory mechanical pump was. The plate has a threaded hole in the center to accept the knock sensor for the ECM. This detects engine knock and automatically retards the ignition timing.

Other sensors used on this system include the MAP sensor, which along with the O sensor determines how much fuel to add relative to the throttle opening. The opening is measured by the throttle-position sensor. The system also includes its own fuse-block and fuel-pump relay.

The throttle-body has a return outlet that needs to be connected to the stock 1/4-inch fuel-return line to the fuel tank. The AIR pump was retained on this Jeep and was in the way several times.

The ECM should be mounted under the dash, where it'll be relatively protected from the elements. Because it's based on the GM TBI system, there is a diagnostic port and a check-engine light. Custom chips can be burned to create the perfect fuel and spark curves for your modified Jeep. We snapped the check-engine light into a hole in the dash.

You should perform a couple of prestart checks, such as making sure the fuel pump runs for 2-6 seconds when the key is turned on and that the engine light comes on for a second to verify that power is reaching the ECM. Also, check for fuel leaks. Then you're ready to start the engine. Our initial testdrive indicated that the exhaust was completely clogged, so Turbo City installed a Car Sound catalytic converter and a DynoMax performance muffler. Turbo City offers complete high-flow exhaust systems for YJs and TJs and the parts you'll need to piece together a similar system for CJs.