Ditching the Opti-Spark on a Gen II LT1 and installing it into a B-body

I thought this day would never come. The joys of doing something no one has before, or that there are no plug-and-play kits for, is that it often takes a great deal longer than you can imagine. Whereas someone like myself has a panic attack when looking at more than two wires that must be soldered and reconnected, Greg Lovell at AntiVenom dove right into wiring up a custom harness for an EFI Connection 58x conversion on his 1996 Impala SS. If you recall from the 396ci LT1 buildup a few eons ago, Greg installed all the mechanical parts when assembling the bottom-end. We strapped the solid roller, 13:1-compression beast to the dyno with a carburetor and it made 576 hp. The eventual goal is to hit that magical 600hp mark, which we may do with more testing. The immediate goal, however, is to get the B-body back on the road. It’s been far too long.

The EFI Connection 58x is a universal kit of sorts for the LT1, which will allow you to convert any Gen II to a Gen IV ECM with individual coils, electronic throttle body, Flex Fuel capability, and compatibility with a 6L80E automatic. Greg planned to take advantage of these added features to get the most out of the stroker LT1 in the heavy B-body. For the time being, though, the transmission of choice is a 4L80E, which will bolt right in using a crossmember from Clear Image Automotive. The crossmember was designed to work with Clear Image’s stainless steel headers and exhaust, which we were happy to use, as well. Frankly, there are very few exhaust options for the B-body that can really take advantage of such a stout engine combination. Past experience has shown that stock manifolds or shorties would seriously choke this engine. The stepped 1 7/8- to 2-inch primary Pro Series headers are made of 304 stainless steel and boast aircraft style V-band flanges on the 3-inch collectors. Normally, an adapter flange is needed with headers this large (on an LT1), but Clear Image started with a clean sheet on these headers. The rest of the exhaust is made of aluminized 3-inch tubing with SpinTech Street XL mufflers. After all, it is still a “street car.”

Some of the finishing touches to this combination include an intake elbow from Edelbrock to mount an LS3 throttle body and a Hawks Motorsports alternator relocation bracket. Greg has been working on a custom electric power steering setup and a way to mount an A/C compressor. For the time being, no accessories will be dragging this raunchy engine down as it finally starts singing on the Dynojet at AntiVenom.

1.To handle 600 hp, you can certainly shell out some bucks for a top-of-the-line 4L60E, but a junkyard 4L80E serves as a nice budget alternative. There was no sense investing big money into a 4L60E since Greg already has a 6L80E waiting. All three can easily be wired in and tuned to a Gen IV ECM.

2.To help a serious solid roller engine breathe, you need a serious set of headers. The Clear Image Automotive Pro Series Headers are available in a few sizes, including 1 7/8- to 2-inch stepped primary with a 3-inch collector. These are ideal for a wild street setup like this. The Clear Image headers are one of the only long-tubes on the market for B-bodies, let alone in this size. The Pro Series headers are made out of 304 stainless steel and feature V-band style collectors.

3.The beefy, proprietary flanges are what really set these headers apart and the key to having such a larger primary. Normally, LT1 guys are forced to run 1 3/4-inch headers or 1 7/8-inch with an adapter.

4.To get started on installing our “Penultimate LT1,” AntiVenom’s crack technician Kyle Miller put the Impala on the lift and supported the 4L60E with a trans jack. After removing the exhaust and crossmember the stock 4L60E was lowered down. The Impala had an upgraded torque converter, which will not be compatible with the 4L80E.

5.Kyle had already drained the radiator, so he got to work at unhooking all the electrical connections and unbolting the PCM. The ’96 Impala SS had an OBD-II PCM, but it is not as easy to tune and doesn’t offer the level of features of a Gen IV (or even Gen III). Plus, in utilizing an EFI Connection kit, you also do away with the dreaded Opti-Spark in favor of individual coils.

6.Thanks to the Impy’s roomy engine bay the stock LT1 was able to come out the top. To make things easier Kyle and Greg Lovell removed the exhaust manifolds.

7.Aside from the block itself and the dipstick, not a single thing on the new 396ci LT1 is shared with the stocker. Not even the fasteners (ARP) or the oil pan (Canton Racing) are carried over.

8.The Impala has so much room in the engine bay that you can leave the radiator and fans in place during R&R with the accessory drive setup installed. After slowly dropping it on to the K-member, the motor mounts were secured.

9.While on the dyno we were forced to use a carb, the plan was to run this Edelbrock elbow (PN 3848) along with the spacer and an LS3 throttle body in the Impala.

10.The Clear Image headers are installed from the bottom with the O2 sensors screwed into the bungs.

11.The 4L80E and converter were then lifted into place using a trans jack.

12.Once the converter and trans were bolted up, Greg and Kyle installed the Clear Image tubular trans crossmember. Four different versions are offered for the Impy (4L60E, 4L80E, TH400 and T-56). The 1 3/4-inch tubular steel piece is a few pounds lighter than the factory one, and is essential to running the Clear Image 3-inch exhaust that tucks tightly to the floor. Notice the round piece on the driver side?

13.This is where the installation got tricky, which caused our installation delay. The original plan was to use an E38 ECM from a 2010-’15 Camaro SS. After making a custom wiring harness, Greg discovered that only the E67 (from the 2012-’15 Camaro ZL1) with a Trailblazer SS operating system and accelerator pedal would allow complete functionality of the Impy’s factory equipment like the ABS module (by accessing serial data) and have cruise control. Of course, re-writing the operating system on a Gen IV with a new VIN isn’t as simple as plugging in HP Tuners. AntiVenom now has all of these capabilities and can build any custom Gen IV ECM or engine swap in-house.

14.With virtually no stock parts left on the engine, there was no point in using the ugly OEM accessory brackets so we called Hawks Motorsports (formerly Hawks Third Gen) for a set of alternator relocation brackets. The kit was designed mostly for race-only setups, but Greg has plans to keep A/C and power steering. The side benefit is that you can run normal SBC valve covers instead of having that massive notch on the passenger side.

15.Greg meticulously assembled the wiring harness to hide as much as possible. You’ll also notice the -AN fittings and braided lines in lieu of rubber and worm clamps. To finish off the install, Greg went with a C6 Corvette’s cartridge style MAF in a 102mm Halltech housing with a C6 air filter. The injectors are Siemens 60 lb/hr squirters from Accel.

16.The E67 is easy to differentiate by its three plugs. Greg mounted it on the driver side, by the master cylinder. It has many features that the E38 (and its predecessors) do not, including injector tables with a larger range to support more power.

17.Greg used electric fans from a 2010 Camaro SS along with an aftermarket radiator to replace the crusty stock parts that were in the engine bay.

18.With the Clear Image X-pipe installed, you can see how it threads through the crossmember and stays tight to the floorpan.

19.Clear Image offers full stainless steel exhaust as well, but we opted for aluminized 3-inch tubing so we could spend the cash elsewhere. All tubing is mandrel bent in-house. Louder mufflers are also available but the SpinTech Street XL is an ideal choice for the street.

20.Since Clear Image makes this exhaust for several B-body variations and various chassis differences can make the length tricky, some tubing is needed to mate to the tips. The over-axle pipes and all the bends were in the right place; it was just a matter of adding this short straight piece to mate to the polished tips.

21.In case you are wondering, the LS1 coils were mounted along the frame well out of view. Plug wires were cut to length.

22.Running on mere 93-octane pump gas, the 13:1-compression LT1 made 509 rwhp at peak and 475 lb-ft of torque. The eventual goal is to switch to pump E85 with a Flex Fuel conversion to push a few more degrees of timing. It is already seeing 34 degrees full advance. Greg has a few other tricks up his sleeve to push this combo even harder.