Metal Works Classics

LS Conversions

LSX 454 LS CONVERSION: GM Performance LSX 454 Chevy Crate Engine

1978 Pontiac Trans Am with a Pontiac 400 motor converted to a GM Performance LSX 454 Chevy Crate engine:
  • LSX 454 620hp by GM Performance
  • Heidts 4 Link Rear Suspension
  • Wilwood 14" Brakes
  • Tremic TKO Transmission
  • Holley Ultra HP Carburetor
  • LSX Camaro Headers
  • LSX Ignition Controller
  • Ford 9" Rearend
  • Heidts Tubular Control Arms
  • LSX Intake Manifold

LSX 454 GM Performance Engine

  • LSX 454 620 hp Crate Engine
  • Displacement: 454 CID, 7.4L
  • Bore & Stroke: 4.185" x 4.125"
  • Compression Ratio: 11:1
  • Block: LSX Cast Iron w/ 6 bolt cross bolted main caps
  • Crankshaft: 4340 Forged Steel, with 8 bolt flange
  • Cylinder Heads: Aluminum LSX LS7 Rectangular style ports
  • Vintage Air Front Runner Kit

Wilwood Brakes

  • Wilwood 14" Rotors Front & Rear
  • Wilwood Calipers 6 Piston Front / 4 Piston Rear
  • Wilwood Brake Master Cylinder
  • Wilwood Clutch Master Cylinder


  • LSX Carbureted Intake Manifold
  • Holley Ultra HP Carburetor
  • LSX Ignition controller
  • Dynatech MuscleMAXX LSX Camaro headers


  • Ford 9" Rearend
  • 3.50 Posi
  • Tremic TKO 600 Transmission
  • Heidts Tubular Control Arms
  • Heidts Rear 4 Link
  • Quicktime Bell Housing
  • 18" Billet Honeycomb Wheels

The Story Behind the Car:

1978 Pontiac Trans AM LS Conversion: this car was brought to us by local owner from right here in the Eugene, Oregon area. When he first came to talk about it he wasn't totally sure what kinds of performance upgrades he wanted to do. He had recently purchased the car in the Phoenix, Arizona area. This 78 Trans AM had already been through a restoration prior to his purchasing the vehicle. The owner was looking for MetalWorks Classic Auto Restoration to take it from good to great!!

After some discussion and looking at options the owner quickly decided he wanted a lot more power under the hood. The current Pontiac 400 6.6L was doing fine but he wanted to blow away the old Smokey and the Bandit days with a new LSX 454 620hp GM Performance Crate Engine. LS Conversion it is!! The owner knew we had recently completed a few other LS Conversions and wanted his on the list.

Once he made the commitment to this kind of serious horsepower it made the rest of the upgrade decisions pretty easy. Upgraded to Wilwood Racing Brakes, upgrade the suspension to Heidts front and rear, and add on some new wheels and tires. We made these suggestions, discussed the details involved with doing an LS Conversion, showed him some visual concepts to see what things should look like, and put some numbers to the project. Even though he had just spent $20,000 on the purchase of the car he was all in and ready to go!!

The first step for this LS Conversion was the suspension upgrades. We started with the Heidts suspension parts front and rear. Heidts 4 Link in the rear with a new 60" wide, 31 spline Ford 9" rearend. Heidts tubular control A arms on the front end. Next was the brake upgrades, and LS Conversion ads so much more power we have to know the driver can slow down and stop the vehicle. As much as we love the power of an LS Engine, safety is first. From the braking standpoint this means a call to Wilwood Engineering for brakes. Wilwood 14" brake rotors front and rear, 6 piston calipers on the front, 4 piston calipers in the rear. We also used Wilwood Brakes brake master cylinder & Wilwood Brakes clutch master cylinder.

For wheels we wanted to give this bad boy a bitchin new look but keep some of the original Smokey and the Bandit at the same time. We opted for new 18" Billet Honeycomb wheels. As you can see they really added to the look while keeping the retro touch at the same time. A 1978 Trans Am with an LS Conversion is way too cool to not have killer new wheels like these.

Next was the engine and drive train. We've done many other LS Conversions but none before came even close to the horsepower of this one. LSX 454 Crate Engine by GM Performance. With 620 horsepower packed into this LS Engine leaves no worries about not having enough power. Every other LS Conversion we've done we used a computer controlled, fuel injection system. However, this LS Conversion it was decided that, to keep costs down, we would go the carbureted route. We used a Holley Ultra HP Carburetor to mix the fuel for this GM Performance LSX 454. To go with the Holley Ultra HP Carb we used an LSX Carbureted Intake Manifold & LSX ignition controller. While we were shopping for the Holley intake parts we picked up a Holley LS retro fit engine oil pan to fit the underside of this LS Conversion project.

To dress up the front of the engine we chose a Vintage Air Front Runner System. Vintage Air makes a beautiful Front Runner system for the LSX 454 engine. For the exhaust side of the engine we went with Dynatech MuscleMAXX LSX Camaro Headers. These were just the right fit for the tight area we had in the engine bay. We went through several sets of headers trying to find a pair that fit correctly before we landing with these LSX Camaro Headers.

Last thing was getting the power from the engine to the rearend and wheels. The transmission of choice was a Tremic TKO 600. With the Tremic TKO trans we used a Quicktime bell housing.

With this project being the only LS Conversion we've done using a carbureted intake we couldn't wait to see how the initial firing of the engine when. When the time was right to fire it up it started right up and ran perfectly just like every other LS Conversion we've done. It's truly amazing what quality of engines Chevy / GM Performance offers. Power, Performance, Durability, and Fuel Efficiency!! That's what makes the Chevy / GM Performance LS line of Engines our choice for engine Conversions.




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