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.