Before we begin, let us recap the premise of this story. In our October 2008 issue, we did a story called "Generation Gap." In it, we took a stock 5.3L LS1 engine from a wrecked '02 Suburban, then dyno'd it. It made 340 hp and 370 lb-ft of torque. After that, we added a Comp cam, Edelbrock cylinder heads, and long-tube headers and made another pull on the dyno. This time the numbers were 441 hp and 410 lb-ft.
Alas, when we last left the little 5.3L engine, it still had the OE truck intake and Summit 80mm throttle body. Believe it or not, that truck intake is pretty decent for torque and hp, but is that the be-all, end all? Obviously, the answer is no. FAST (Fuel Air Spark Technology) has a new LSX 92mm intake on the market made of stronger composite materials than the OE manifolds. FAST claims the new LSX 92mm intake will add 20-plus horsepower to the Gen-III LS1, LS2, LS6, and LS7 engines. Since we are using a 92mm intake, we thought it prudent to upgrade the throttle body from the 80mm unit to the FAST Big Mouth 92mm throttle body engineered specifically for this intake. We also opted to ditch the OE 24-pound fuel injectors and upgrade to FAST 36-pound fuel injectors.
Once everything was said and done, we were quite surprised at how much horsepower we picked up. The former peak number was 441 hp at 6,200 rpm. The new number now stood at 475 hp at 6,400 rpm. That is a gain of 34 hp. We did, however, lose small amounts of torque at the bottom end of the rpm chart.
Better airflow than 80mm units due to enlarged throttleopening and refined internal designDual-throttle spring mechanism and beefed-up throttle linkage for total throttle controlIncreased thickness, throttle blade and shaft resistsdeflection, especially in boosted appsSmoother operating, offset blade pivot for improved throttle response
Bolt-on performance gain for Gen-III applications (LS 1, 2 and 6)Longer, tapered runners increase high-rpm hp, yet retain torqueLighter & stronger polymer construction avoids heat sink effectThree-piece design allows easy access for porting & modifications25 percent increased plenum volume for less intake chargeturbulenceOptional burst panels for increased safety with nitrous or forced inductionMolded-in bosses support machining for direct-port nitrousinjection nozzlesThree-piece design allows easy access for porting and custom modifications
Now it is time for some prices. We searched the Summit website to get our dollar figures.
FAST LSX 92mm intake: $879.95
FAST Big Mouth Throttle Body: $474.99
FAST 36-lb Fuel Injectors: $339.95
FAST billet aluminum fuel rails: $209.95 (even though we didn't have these for the build, we should have)
For a total of $1,904.84 we gained an extra 34 horses and slightly increased the engine's rpm and torque. Is it worth it? It depends on whom you ask and what they intended to do with their engine. All we know is that we gained more than the advertised 20-plus horsepower and it works.