Typically you can expect to see the following engine/horsepower combinations while taking into account your cubic inches versus horsepower: 305 ci should require 19.9lb injectors; 350-inch with 225-275 hp can use 21.9lb injectors; while 300-375 hp (ZZ4, 350 Ram Jet, LT1, and LS1) utilize 24.9lb injectors. The 405hp LS6 uses a 28lb injector and big-blocks (425-550 hp) use a 30lb injector, while the 502 Ram Jet uses a 38lb injector. (Word to the wise, use new injectors or have them cleaned with an ultrasound injector cleaner on a flow bench by a professional before firing your engine.)
Camshaft
Fuel-injected engines have significantly different demands than their carbureted brethren and as such, to achieve optimum performance you may wish to look at a camshaft swap. (Plans call for us to make this camshaft swap and we will publish the results.) We visited COMP Cams after the NSRA Nats in Louisville and gathered great info on this conversion.
COMP Cams has specifically designed for electronically controlled fuel-injected engines a new line of XFI camshafts. A carbureted engine requires a strong signal or airflow at the carburetor booster to draw the correct fuel into the engine. Since that excess flow is not required in a fuel-injected engine, overlap and low lift flow requirements are not as critical. You will need a cam with wider lobe separations and higher lift. This also takes advantage of the newer-style intake ports, manifolds, and combustion chamber designs. Both intake and exhaust lobes feature increased area, which equates to higher airflow and horsepower.
Ram Jet Fuel
Injection Kit
While there are many ways to go when converting from carburetion to fuel injection, we are particularly fond of the GM Performance Parts Ram Jet Fuel Injection Kit (PN 12498032). It comes with all the hard parts minus the electronics. It's intended to be used with steel or aluminum Vortec heads.
Engine Control Unit
FAST stands for Fuel Air Spark Technology-or as I like to call it, "the brain behind the brawn." The FAST XFI system (computer) is intended to balance fuel, air, and spark, allowing.
Your engine to be fine-tuned as you drive. FAST XFI software will download to your computer (in our case a laptop), allowing you the advantage of tuning for performance or economy in a fraction of the time with no additional tools. The XFI system comes with easy-to-navigate software that's completely configurable and allows you to set the priorities. This is what makes the fuel injection work as it monitors timing, manifold pressure, air/fuel ratios, coolant and air temps, throttle position, and idle air control.
Next Month
In part two we will get into many of the particulars, such as part numbers and the whys and wherefores of the installation. I can tell you this: After the installation, which took one (very long) day, I jumped on the road from COMP Cams in Memphis, Tennessee, and drove the 1,900 miles home (alone!) and the car didn't miss a beat. I became a bit tired and thrashed from the late-August 104 degree heat, but the car ran flawlessly. Wait until next month.
The days of electronic fuel injection referred to as Black Magic are over. It has taken hot rodders long enough to figure out carburetion, and with the advent of EFI, the fear of "something new" struck deep. That isn't the case any longer.
The movement in the world of street rods toward technology is accelerating faster and faster. Rodding has long been the bearer of "things old," but technology is currently embraced in both its "natural" and "altered" states. Techno rodders are split into two groups: those who embrace technology and its appearance and those who embrace it but want the vintage look. The rush toward technology started slow enough; first there was electronic cruise control, power windows and antennas, digital gauges, electronic ignitions, and then came the computer. It wasn't long before electronics "slipped" into our world of engines, transmissions, and all matters mechanical.
And that brings us to the first of a multi-part series on the whys and wherefores of converting from carburetion to modern electronic fuel injection. To gather the background info, we worked with COMP Cams (fuel injection camshafts), FAST (Fuel Air Spark Technology on computers for engine management), Tanks Inc. (fuel injection gas tanks), Street & Performance (complete EFI engines and accessories), Pure Choice (plumbing), and Lokar (cables).
When entertaining the idea of converting from carburetion to fuel injection, an old axiom comes to mind: "Plan your work, work your plan." Aside from removing the carburetor(s), we will give consideration as to what type of fuel injection, throttle body (atop a carb intake), or a plenum chamber/throttle body style we will want to run. Each has its advantage, whether it's initial cost, ease of installation, and/or which will work best with the engine management system you select. Next up is the gas tank, which now requires a return line; the fuel pump-no longer will your mechanical pump be sufficient-and then there's the matter of an external pump (typically mounted to the frame) or an internal pump (such as an OEM submersible); plumbing, remember you will need a feed line (which you have), but you will require a return line to bring back unused fuel to the tank; revamped throttle cable and at least the upper radiator hose (and possibly rework the water inlet), this isn't difficult as there are components on the market to achieve this goal.
There are a number of minor to major adjustments such as the possibility of finding a new location for your alternator, new air cleaner positioning, and finding a home for the engine control unit (CPU, computer) and the wiring loom (more wires for a complement of sensors).
Fuel Delivery System
Let's begin this project at the back and work our way to the front. The gas tank and the fuel pump are important decisions to be made before you purchase any of the fuel injection components. The gas tank will require a feed and a return line. Always use fuel line that is rated for fuel injection use as the pressure with this system is greater than that of a carburetor-equipped engine. Hard line, rated rubber, or stainless steel braided line will work with a 3/8-inch supply side hose and a 5/16-inch return hose.
You will have to make a decision on external or internal (submersible gas tank) fuel pumps. There are things to take into consideration with both, but we will get more into that in part two. However, two experts in the field, Mark Campbell of S&P and John Pazik of Tanks Inc., prefer the in-tank fuel pump for several noteworthy points: smooth and quiet operation, fuel pump is cooled (helps to eliminate vapor lock) by the very gas it resides within, and much longer pump life expectancy.
You will need to replace your fuel lines within the engine compartment as well as come up with fittings that get the job done and look good as well. We dropped by Pure Choice at the Nats and picked up some fittings, fuel filter, and bracket as well as some good info.
Injector Size
This is a tough one for street rodders since we all think our engines produce gobs more horsepower than they really do. Just as in carburetors, oftentimes smaller is better.
