Replace Your Carburetor With A Multi-Point Injection System From Holley

Carburetors have been around for what seems like centuries. They did a great job supplying fuel to Corvettes up until ´81, when performance took on another consideration: efficiency.

Andy Bolig Nov 1, 2000 0 Comment(s)

Step By Step

The first step was to get rid of the carb and intake. The MPI's 1,000-cfm capabilities will easily flow enough to equal this carb.

Disconnect the fuel line, drain the water from the engine, and remove the upper water hose and distributor. After that, remove the entire carb/intake assembly.

Before you go any further, make sure the machined surfaces on the head and the top of the block are clean. There should be no old gasket material on either surface. Don't let any material fall into the intake ports, and put a rag or a towel in the lifter valley to keep foreign material out of the engine. Make sure that the ports and lifter valley are clean before you install the intake gaskets.

For the front and rear gaskets, Chris at Corvette Clinic uses Permatex Hot Oil Resistant Silicone Sealer. Make sure to overlap the corners of the side gaskets so you don't get an oil leak later.

When it's time to install the MPI unit, make sure to place it as square as possible so you don't disturb the gasket surfaces. Note that we removed the fuel rails. This makes it easier to reach the intake bolts.

We used ARP bolts to hold the intake in place. When you install them you should take the time to treat the threads to prevent any leaks.

The outer bolts on each side get an antiseize; the four inner bolts get thread antiseize/sealant because they protrude into galleys inside the head.

Snug the bolts evenly and then torque them in steps, alternating side to side, and starting from the middle and working your way to the outer bolts. Torque the bolts to a final setting of 30 lb-ft.

With the intake bolted on, you can reinstall the fuel rails and tubes that unite the two fuel rails together. Apply light oil on the O-rings and be careful installing the injectors into the intake; they fit tight, but you shouldn't have to stand on them to insert them. Don't forget to hook up the vacuum line that operates the fuel-pressure regulator.

Using the old brackets and the parts supplied in the kit, hooking up the throttle and kick-down linkage is a clean and easy operation.

The injectors are numbered, so there's no question which injector lead goes where.

Next, hook up the idle air control and the intake air-temp sensor (located right below the IAC).

Chris then hooked up the manifold absolute pressure sensor. This sensor helps the computer determine how much fuel is required.

The water temperature sensor was next. Use thread sealer, and remember, the intake is aluminum so it's much easier to tighten the sensor a little more than to have to rethread it.

We used a set of headers that were already equipped to use an oxygen sensor. If you don't have provision for an oxygen sensor, you'll have to modify your exhaust to accept one. This sensor is not an option.

The last sensor we installed was the oil-pressure sensor. The computer needs to know that the engine has oil before it will allow the rpm to increase.

Chris had to bend up a new fuel line because the MPI unit comes with an electric fuel pump and uses the pressure regulator with a return line to keep the pressure at usable levels.

While we were working on the top of the engine, we decided to install a Pertronix ignition.

Only the most keen-eyed observer will be able to tell that you're not running the original set of points. This will bring your once point-operated distributor into the dependability of today's electronic distributors while retaining the look of originality. This is also a benefit if your distributor has a tach drive.

We opted to go with the Strip Annihilator Ignition system...

...coupled with the Laser Shot Pro Coil...

...and 90-degree, heavy-duty plug wires for a trouble-free ignition.

The Laser Shot coil was mounted on the firewall.

While we were cutting and trimming the spark plug wires, we put on Holley's heat shrink numbers so we'd never have to guess which wire goes where.

With the addition of a PCV tube in the driver-side valve cover and a new upper radiator hose, all we needed to do was add water and the underhood portion of the install was complete.

Chris decided that the best place to install the computer to run the system was upside down in the passenger side of the dash.

Chris decided to use an internal fuel pump. To do this, he modified an original ´73 sending unit by replacing the 1/4-inch return line with a 5/16-inch line. A fuel-pump power wire was installed in the sending unit. Any pre-´77 GM fuel-tank sending unit has a removable power lead connector. A hole must be drilled to install the connector for pump power. Solder the ground wire to the sending unit and make sure that the sending unit has an external ground to the frame. The fuel-pump power and ground wires must be fuel resistant, and can be obtained from any ´87 or newer GM product located in a salvage yard.

Corvette Central supplied us with new rubber tank straps and inlet seal.

With the modified tank receiver installed, all we needed to do was run another wire for the fuel pump and install the tank again, and our installation of Holley's MPI fuel injection is complete. Sort of.

When fuel efficiency became the watchword, It was no longer enough to supply horsepower-producing fuel and air ratios; now the Corvette's fuel system was required to do that and be fuel-efficient and more environmentally friendly at the same time. Those standards simply could not be met with a carburetor mentality. Evidence of the benefits to changing to a fuel-injection system is revealed in aftermarket manufacturers' systems designed to fit on applications where for years a carburetor had been the only choice. Corvette Fever had an opportunity to install Holley's Multi-Point Injection onto a previously carbureted ´71 Corvette. Here's what it takes to ditch the carb and make your engine run lean and mean.

COMMENTS

subscribe to the magazine

get digital get print
TO TOP