Jeff Smith: We're about to embark on a buildup series on a 5.3L GM LS-series engine, since it is by far the most prevalent of the LS engines. According to one GM source, an unofficial estimate places 5.3L production numbers at more than 14 million just since 1990. The 5.3 uses a 3.78-inch bore and a 3.62-inch stroke, creating a displacement of 326 ci. The obvious comparison is with the original '62 to '69 327 small-block Chevy, but that early motor used a larger 4.00-inch bore and a 3.25-inch stroke. The 5.3L suffers from a smaller bore, yet still offers excellent overall power and torque. You should be able to wrangle 310 to 320 hp out of a stock engine equipped with headers, which is close to 1 hp per ci. To bolt it into your Firebird, you could eliminate the EFI and swap on an Edelbrock carbureted-style dual-plane intake manifold and ignition conversion box that's all under one part number (7118, $649.95). The timing control module drives the distributorless igni-tion with interchangeable chips that establish the timing curve, so no laptop is required. Using a carburetor instead of EFI might add another 10 to 15 hp with the stock cam, and it will probably make around 350 lb-ft. With a little carb tuning, you should be able to pull down decent fuel mileage. Swapping the 5.3L motor into your Firebird isn't difficult but will require a different oil pan, headers, and motor mounts, which are available from companies such as Hedman or Hooker. Stay tuned for a complete story on those swap details. Also be aware that the truck accessory drive will work, but it's a bit clunky. If you want to convert to a better-looking system that retains the factory alternator and truck harmonic balancer, take a look at the Kwik Performance swap kit-it's inexpensive and will get the job done. We've used the Kwik Performance kits in the past, and they work very well.
Even if you don't go with that 5.3L right away, definitely dump that frumpy two-speed Powerslide. There are several paths to swapping in a manual five-speed, which would be an excellent combination with the 5.3L motor. We won't go into all the details on the swap ideas, but Keisler has a system as does Hurst Driveline Conversion (it used to be called Classic Motorsports Group). If you don't think you can handle the swap by yourself, Hurst is located just up the freeway from you in Carlsbad, California, and can do it for you. Both companies offer complete conversions with the trans, shifter, bellhousing, clutch, crossmember, and driveshaft. Both use the Tremec TKO five-speed-either the TKO-500 or TKO-600. Choose the TKO-600 because it offers a more ideal 2.87:1 First gear ratio combined with a tall 0.64:1 Overdrive. This overdrive ratio means that if your Firebird's cruise rpm at 70 mph is currently 3,000, the 0.64:1 Overdrive will knock down that rpm to 1,920. This will be worth roughly 2 mpg or more over that Powerglide. These overdrive trans conversions are somewhat pricey-more than $3,000 for an entire kit depending on which options you choose. The Tremec TKO-600 is a great transmission that is light and compact for its strength (rated at 600 lb-ft), and for an early Firebird, it requires no floorpan butchery except the hole for the shifter.
If you've ever seen the movie Ben Hur with Charlton Heston, the bad guy in the chariot race had a set of hubcaps just like these, except the blades were bigger and nastier.