Take a quick look at the specs and the e.t.'s attached to Jeff Green's '96 Impala SS and there is whole lot that (seemingly) doesn't make sense. However, this is clearly just a testament to Jeff's character, the sort of rare breed that bucks convention and popular opinion—defying the odds to make what many would say is impossible, possible. Fueled on disbelief and pump gas, Jeff's Impala runs a stout 9.5 at 153 mph without even the slightest attempt at weight savings, which is quite a feat in itself for a lead sled like his B-body that can be driven to and from the track. Couple that with the fact that he does it using a factory computer, Optispark distributor, 4L60E trans, and 8.5-inch 10-bolt—and this Impy is quite the head scratcher.
Clearly accomplishing this task takes quite a few tricks and lots of trial and error. Establishing a reliable and potent powerplant was the first and possibly most crucial step, it takes a lot of power to move over 4,500-pounds into the single digits. At around the 10.30 mark, Jeff no longer felt confident in the factory block, which, keep in mind, needs water pumping through it since it's a streetcar. Jeff's solution was to make his own “LTX” block–starting with the small-block style aluminum Donovan 400, which has been extensively machined and welded to accept all of the LT1 sensors and accessories including the factory water pump and Optispark. Besides internal strength, the aftermarket block had several advantages such as splayed main caps and a larger bore—try building a 434-cube motor with a stock LT1 block! The cog-driven Paxton Novi 2000 supercharger has played havoc on the bottom-end while driven up to 19 psi, so a top-of-the-line Bryant crank is used to swing the Oliver NASCAR-style rods and Wiseco slugs. For streetability, a hydraulic roller cam was the natural choice, spec'ing 248/258 in duration. The top-end consists of a factory LT1 intake manifold, Holley 58mm throttle body, and AirFlow Research's 227cc LT4 heads, which have been worked over by Indy Cylinder Head to include Manley 2.10 and 1.60 Titanium valves.
Utilizing the factory intake proved to be a very challenging move, especially in combination with a factory PCM. Without the ability to change fueling on each cylinder, Jeff found that changing the intake rocker arm ratios and fuel injector sizes helped him achieve the proper air/fuel that would keep him from burning up pistons. An 8-channel wideband O2 was crucial in diagnosing this problem and dialing it in. Jeff also utilizes a low-impedence injector driver for the 96 and 110 lb/hr squirters, an Accel in-line pump for the street, and then a second big-boy Weldon pump that is only active at wide-open throttle. The induction system is equally as trick, using a modified bracket from Paxton (for one of its smaller blowers), a Novi 2000 race blower sucks through an LS1 F-body MAF, which has been recalibrated to work in this extreme application. To keep the MAF happy, a Paxton bypass valve recirculates excess boost to the charge tube, however, at the track a second bypass vents to the atmosphere. In lieu of an intercooler, a small shot of nitrous chills the charged air.
Also helping to relieve pressure is a beefy exhaust system, which actually runs all the way to the back bumper (thanks to BC Race Cars). A custom set of stepped headers measure 2-inches in diameter at the exhaust flange then increases to 21⁄8 and then 21⁄4 before terminating in a whopping 4-inch collector. The 4-inch pipe follows its way all the way to the back, using a balance pipe to equalize pressure and Flowmaster mufflers to quiet the ruckus. The overall combination provides plenty of low-end grunt that shatters 8.5-inch ring gears at will, yet somehow the Rossler-built 4L60E keeps living. When launching on a set of Hoosier 28x11.5 slicks, Jeff has even bent a rear sway bar. The more substantial Competition Engineering anti-roll bar seems to provide enough rigidity, however, if Jeff is going to break into the 8s he is going to need to keep the ring gear in one piece. Though the obvious solution would be to add a 9-inch, his insistence on keeping the 10-bolt has led Green to start adding more top-end power at the expense of torque. A larger cam, intercooler, NANO pusher system, and an Arizona Speed & Marine 1,300-cfm throttle body are just a few of his latest changes.
Building a streetable 9-second car with air conditioning, power steering, power windows, and all the amenities has become so easy these days that it is almost unremarkable until someone like Jeff Green chooses to do it in a 4,500-pound B-body with as many factory components as possible. Clearly Jeff is just the sort that thrives on this sort of challenge—he did teach himself tuning once some of the best in the business threw up their arms over this beast. Green took the road less traveled and triumphed. It is an old story that is constantly retold with more remarkable examples every time, which serves to give us all hope.