At GMHTP, we cater to all years of GM EFI muscle, and the LT1-powered GMs are no exception. Though today overshadowed by the much-adored LS1 and LS6, the LT1 can be made to run with many of the newer cars with just a few relatively straightforward modifications. A prime example is that while the LS1 ignition system is hot right off of the showroom floor, the LT1 can benefit from a little help, thanks to its old-fashioned single coil and dreaded Opti-Spark distributor. The stage is set; here come the goods.
A plethora of ignition systems are available on the market, but few pack as many features as Crane Cams' FireBall HI-6. This fully digital, multi-spark, capacitive discharge ignition is designed for both street and strip use. Crane's box is literally a plug-and-play deal, and offers up to 12 sparks per firing event below 3000 rpm. This means better torque, fuel economy, and throttle response thanks to a more efficient burn of the air-fuel mixture. At the high end, you get a single high-intensity spark for maximum power output--even with nitrous, blowers, turbos, and up to 14.5:1 compression ratios. The box will supply a spark up to 12000 rpm, though your LT1 will likely not need this (And if it does, we'd really like to hear about it!). Just beginning the buildup of his 1997 Z28, Jason Becker of Bergenfield, New Jersey was eager to volunteer for a test of Crane's system. His 101,000-mile car will soon be receiving shorty headers and a cat-back exhaust system, among other go-fast goodies, and the Crane FireBall will be an integral part of the power package. Follow along in the photos as we go through the installation of the Crane box on Jason's car.
As any owner knows, "cramped" is not a harsh enough word to describe the engine compartment of a fourth-generation F-car. Hence, one of the main holdups on this install was finding a place to mount the FireBall box. While measuring only 8 inches long, 4.5 inches wide, and 2 inches high, this still posed a challenge to the installers. While we tried hard to fit the box in various other places in the engine compartment, we ended up going with the driver's side fenderwell adjacent to the fuse box. Others have mounted ignition boxes inside the interior of the car, but that involved too much running of wires for us, not to mention possibilities of wire chafing on holes drilled in the firewall, improper wire lengthening, and further cramping of the passenger footwell.
Also needed to complete the installation was Crane's Single Channel Electronic Trigger, necessary for 1996 and later OBD-II vehicles. This device prevents the triggering of diagnostic fault codes and that pesky check engine light. Finally, we also required Crane's LT1 Adapter Harness, which makes installing the HI-6 a literal plug-in to the factory weather pack connectors. Note that non-OBD-II LT1s (in general, 1995 and earlier) won't need the Electronic Trigger, and will also use a different Adapter Harness (part No. 6000-6708) since the coil on those cars is of the two-plug HEI type and not the single-harness plug of later cars. Check which coil your car has before ordering.
Believe it or not, there is a chance that some OBD-II cars will not need the Electronic Trigger, but this will depend on your individual application's OE computer and any aftermarket programming. According to Terry Johnson at Crane, "This has been a source of headaches for not only Crane, but the rest of the electronics industry. In fact, computers that are identical save for a slight difference in build date may differ in their need for the Electronic Trigger. But the odds are that you will need this item for your OBD-II car, and it is not worth risking the triggering of engine codes. It is just one of those things where there is no way to know until an ignition system is installed."
Though Jason's car didn't get it, an optional Timing Retard Control is available that plugs right into the HI-6 via a separate "weather pack" connector--unused in our application and simply capped off. This nifty module involves a knob that mounts inside the cabin in order to deliver user-selectable amounts of timing retard. This module can be connected to a MAP sensor for boost-proportional retard (such as 4 degrees per psi), can be wired into a nitrous system for instant retard as the nitrous solenoid opens, or can simply be left active all the time so that the driver can dial in exactly the amount of retard desired at any given moment. This option may prove particularly useful should Jason decide on a power adder of some sort down the road.
As is customary at GMHTP, we were planning on giving you a dyno test of this system to get some real numbers, but due to unforeseen circumstances we couldn't do it in time to make it to print. We apologize and hate printing an article without horsepower numbers as much as you hate reading one. Rest assured, however, we will have the full results for you in an upcoming issue. Keep it here.
The Crane Difference
There are quite a few ignition manufacturers out there, so why Crane? First of all, remember that Crane's HI-6 is a digital system, and has been so since 1995. Other manufacturers continue to offer less expensive analog units and have only recently started offering digital boxes.
While there is no true apples-to-apples comparison between one manufacturer's box and the next, since no two manufacturers offer boxes with identical features, several generalizations can be made about Crane's advantage. Terry Johnson of Crane says, "One of the things that really sets Crane apart is the attention to quality that goes into our boxes, and this starts with our surface mount board construction. Crane's boxes are robot-manufactured and tested during each step of manufacture. The machines actually test each component as it is attached to the board! Having no humans with soldering irons involved not only minimizes the chance for mistakes, it also allows miniaturization of the board components. This allows the parts on the board to be not as tall and thus far less susceptible to cracking under temperature extremes and intense vibration. Every unit is also fully sealed with soft urethane for the ultimate in component protection."
The HI-6 comes with a built-in digital sequential rev limiter that is accurate to plus or minus 30 rpm. Sequential firing minimizes stress on the engine while the rev limiter is active by firing all cylinders equally in rotation, while keeping the rpm within a narrow band. Unlike other companies' limiters, Crane's system never drops the same cylinder twice in a row, and hence the limiting action is almost seamless, with none of the harmful popping and banging often heard at drag strip starting lines. Crane makes limiter adjustment easy with little rotary dials that are built into the side of the box.
On a similar note, Crane's box offers "cross-fire" protection. According to Terry, "This phenomenon occurs when distributor-type ignitions actually end up firing the wrong cylinder due to there being an easier current path to simply jump to the next prong inside the distributor instead of firing the cylinder that is ready for an ignition event. This is a particular problem under the high cylinder pressures of forced induction. The HI-6 unit can actually sense if the spark is jumping to the wrong cylinder and will instantly take steps to stop it; for example, it can go into single-strike mode instead of multi-strike mode if the rpm is below 3000." The result is more power and less danger to the engine.
For those of you who enjoy monster tachs staring you in the face, Crane makes it easy to hook them up through the built-in tach output "weather pack" connector. No more pulling the instrument cluster and staring in disbelief that the gauges are all computer controlled and you can't jerry-rig in a tach or shift light! Plus, turning the rev limiter rotary switches to either 03 or 04 enables either a step or ramp tach test feature so you can make sure you have it all hooked up right.
Another cool feature of the HI-6 is the LED status/diagnosis light located on the left side of the HI-6 box, near the rpm limiter dials. Normally, this light will blink rapidly to indicate a valid trigger signal when the engine is cranked. If something goes wrong, the LED will blink a certain number of times to tell you what is wrong. For example, 3 blinks followed by a short pause indicates that the ignition coil has shorted to ground.
These are just a few of the things that help set Crane's ignition systems apart.