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Force-Fed 383

Who Says Late-Model LT1s Aren't Hot?

Barry Kluczyk Dec 19, 2005

If your memory stretches back to when the Spice Girls were hot, when eBay was used for swapping Beanie Babies, and when cars still came with cassette players, you might recall that our editor, Terry Cole, had been messing around with a much-modified, LT1-era Z28 convertible around that same time.

Among its many aftermarket accoutrements has been an ATI ProCharger-huffed stock-blocked engine. It certainly ran well, but a few too many overly enthusiastic commutes to the office took their toll. Awhile back, the head gaskets went the way of Macarena--downward.

Tired of mopping up the puddles on the garage floor, Mr. Cole decided to have the small-block rebuilt--and in the true hot-rodding spirit, he followed the if-it-blows-up, rebuild-it-bigger mantra. The question then arose: where do you go with a combination that already was supercharged?

The answer was pretty easy: keep the supercharger and add more displacement. With that, the Camaro project was reborn. Here are the points to the basic plan:

* Yank the worn-out factory 350.
* Replace the engine with a 383ci short-block from Scoggin-Dickey.* Install one of Pace Performance Warehouse's LT4 conversion kits (heads, intake, etc.).
* Bolt-on a new ATI ProCharger P-1SC supercharger and intercooler system.
* Run the combination on an engine dyno in both normally aspirated and supercharged configurations.
* Shove the works back into the Camaro and run it on a chassis.
* Sweet talk Flint, Michigan's Hardcore Racing into doing all the work and dyno tuning.
* Bring the car home and reintroduce it to neighbors who had thought they'd seen and heard the last of that "damn white Camaro."

As is the case with all projects of this magnitude, logistics were more difficult than collecting the parts for the job. The project would require an extended stay at the host shop while all the work was performed. It would also require some expertise in engine building and dyno tuning.

The basics
Dropping the old engine out of the car wasn't a chore. The engine was then removed from the crossmember, as some of the parts would be needed on the assembly of the new engine.

Rather than build a 383 from the original 350, we let our fingers do the walking and ordered a 383 short-block assembly from Scoggin-Dickey Parts Center (SDPC). The engine was one of its custom-built kits, rather than one of the GM Performance Parts assemblies with which it is more commonly associated. We elected the custom engine, as it features more heavy-duty components that we knew our supercharged combination would need.

Some of the parts in the 383 short-block include splayed four-bolt mains, a Lunati 4340 forged crank, and Lunati Pro Mod 5.850-inch rods. The rotating assembly also is internally balanced. There was an issue, however, when the short-block arrived at Hardcore Racing--it was equipped with Scoggin-Dickey's spec 10.4:1 pistons. That would be too much squeeze for our supercharged aspirations. "No sweat," Hardcore's Eric von Hentschel told us. "We'll pop them out and slip in some low-compression pistons." Von Hentschel handled all of the engine work for this project.

LT4 on top
Riding atop our 383 will be a complete LT4 conversion kit from Pace Performance Warehouse--at least, all the parts that would jive with our 383 and supercharger. This kit, which sells for about $2,400, is a terrific way to get optimal performance from a stock-type LT1 engine. The kit is based, of course, on the LT4 engines found in a couple of limited-edition '96 Corvette models. The upgrades include the famed higher-lift "Hot" camshaft, 1.6-ratio roller rockers, high-flow aluminum cylinder heads, springs, and an instantly recognizable red-painted intake manifold with raised intake runners. The LT4 kit also requires a new throttle body and computer reprogramming, but on an otherwise stock LT1, it's good for about 425 hp--a 50-horse jump over early LT1 output. Think about that for a moment: factory-matched heads, intake, cam, and all the details that go with the swap for about $2,400. That's a hard deal to beat.

On our supercharged 383, we are hoping to make the most of the LT4's increased airflow characteristics to help flow more pressurized air through the engine. As was the case with the 383 short-block, a few changes were required to accommodate the supercharger and large-displacement specs of the engine. For one thing, the camshaft was swapped for something more appropriate for the blower with a wider lobe separation. That required some valvespring mods, too--all of which were handled by Crane Cams.

The blower and beyond
With explosive performance generated by the ATI ProCharger on the original 350 engine, we decided to keep on keeping on with a ProCharger. For this project, a P-1SC blower and two-core intercooler system were chosen. The system should make 8-12 pounds of boost, while allowing the engine to be tuned for pump gas. Installing the supercharger will be a multifaceted affair, as it will be temporarily installed on Hardcore Racing's engine dyno for preliminary testing, then disassembled while the engine is hoisted back into the Camaro. All that will be covered in the next installment of this build-up series. On these pages, you'll see how the old engine was removed and the new 383 was built up just prior to the supercharger's installation.

Yes, it's kind of a tease, but if you want to know what a fresh, 383-cube LT1 runs after being topped off with an LT4 kit and force-fed from a ProCharger P-1SC, you'll have to wait until the next issue. We've seen the dyno numbers already. Believe us, you'll want to check them out.


It's a long way from Southern California to mid-Michigan, but Flint is the headquarters for Hardcore Racing and that's where the Camaro was sent for its new engine combination. Once at Hardcore, the guys wasted little time before hiking up the car and getting to work.

Engine removal of Fourth-Generation F-cars involves dropping the front subframe and engine as a single assembly, so much has to be disconnected from the top to provide a free and clear drop, especially the struts and front suspension components.

With the front subframe unbolted and the engine disconnected from everything in the engine compartment, the body is raised slowly and carefully--a job made much easier with a two-post lift.

Here's the nearly 10-year-old powertrain, which is removed with the transmission attached--it's just easier that way.

The 383 short-block was put together by Scoggin-Dickey, but the assembly wasn't originally designed for the lower-compression needs of a supercharged application. So, at Hardcore Racing, the short was disassembled so that new, lower-compression pistons could be inserted.

Scoggin-Dickey's assembly includes a sturdy 4340 forged steel crankshaft from Lunati and it went right back into the block when the reassembly started.

Part of the Scoggin-Dickey 383 kit are forged 5.850-inch Lunati rods. Luckily, the size was right for the new pistons.

The pistons of the Scoggin-Dickey short-block would have delivered too much compression for our street-intended, super-charged combo, so they were swapped for these forged aluminum JE slugs. With the LT4 heads, they should provide about a 9.1:1 compression ratio.

Fortunately, the new pistons' pin-height position was just right for the 5.850-inch rods. Supercharger-friendly rings were added, too.

Before the rod-and-piston assemblies were assembled, the crank was secured via splayed four-bolt main bearing caps--a special feature of the Scoggin-Dickey kit.

With the pistons pinned to the rods, the assemblies were carefully tapped into their respective bores.

The connecting rods were cinched down and torqued to spec. The short-block assembly, so far, is straightforward.

Building a long-stroke 383 requires notching the pan rail to make room for the connecting rods. This photo clearly shows why the notches are needed.

We ordered an LT4 conversion kit from Pace Performance Warehouse, which included GM's famed "Hot" camshaft, but like the 383's original pistons, the Hot cam isn't really suited to a supercharged setup. According to engine builder Eric von Hentschel, the Hot cam's exhaust ramps are long and the lobe separation is too narrow. "Most of the mixture would be burned in the headers with a blower and the Hot cam," he said.

A call to Crane Cams got a blower-friendly camshaft with wider lobe separation. Lift specs are 0.540/0.555 and duration is 213/224 @ 0.050.

If you're not familiar with building LT1/LT4 engines, then this piece will look foreign--it's the water pump geardrive for the reverse-flow cooling system.

Because there aren't many choices in aftermarket timing sets for LT1 engines, this stock-type set was slipped on.

With the camshaft installed, it was carefully degreed by builder von Hentschel.

At the halfway point, the short-block is back together, including a shiny replacement timing cover. As is the case with timing chain set, there aren't really any aftermarket alternatives for the cover, so a stock GM cover was installed.

LT4 Kit at a Glance
As we mentioned in the primary story, the LT4 conversion kit available from Pace Performance Warehouse is a complete system that can pump a stock LT1 to about 425 normally aspirated horsepower. The kit retails for about $2,400 and includes the following components:

* Fully assembled LT4 aluminum heads (2.00-in. intake/1.55-in. exhaust valves)
* Red-painted LT4 raised-runner intake manifold* LT4 "Hot" camshaft (0.525/0.525 lift; 218/228 duration; 110-deg. lobe centerline)
* Aluminum roller rocker arms with 1.6 ratio
* Head gaskets and intake gaskets
* Bleed pipe seals
* EGR gasket and EGR pipe gasket
* Throttle body gasket
* Miscellaneous additional gaskets
What the kit doesn't include is the necessary upgraded throttle body, which maxes the performance of the combination. Computer tuning also is required, as the stock LT1 program won't dig what the LT4 parts are trying to tell it. In all, it's a thorough kit that gives LT1 owners a leg up on the LS1 competition. Check out for more information.

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Scoggin-Dickey Parts Center
Lubbock, TX 79424
Crane Cams
Daytona Beach, FL 32117
JE Pistons
Huntington Beach, CA 92649
Hardcore Racing
Montclair, CA
ATI ProCharger
Lenexa, KS 66215
Tuned Port Induction Specialties
Chaska, MN 55318
Pace Performance Warehouse
Niles, OH 44446

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