LS1 Carburetor V.S. Computer Performance Test - Retro Modern Motivation

The Eternal Fight: Carbs vs. Computers.

Richard Holdener Apr 1, 2011 0 Comment(s)
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With our heads, cam, and intake needs met, all we had to do was install everything onto the awaiting 5.3L short-block and run it in anger on the dyno. Installation went smoothly and required only new Fel Pro head gaskets (5.7L bore size for use with the Trick Flow heads) and ARP head studs. The factory O-ring intake gaskets were swapped over from the truck manifold to the Edelbrock intake and in no time our modified 5.3L was up and running. It should be noted that we used the factory rockers in lieu of a set of aftermarket roller rockers and retained the 1 3/4-inch long tube headers and Meziere electric water run on the stock 5.3L.

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Equipped thusly, the output of the 5.3L jumped to an impressive 462 hp at 6,600 rpm, while torque production now stood at 413 lb-ft at 5,200 rpm. The little 5.3L belted out over 400 lb-ft from 3,900-5,900 rpm, making for one heck of a solid street performer. The healthy Comp cam made itself known by allowing the motor to produce peak power fairly high in the rev range, but even down at 3,200 rpm, the 5.3L still offered 330 lb-ft of torque. It should also be noted that this carbureted 5.3L fired up on the first attempt after hooking up the Edelbrock conversion, an indication that ease of installation was high on the list when developing this system.

With our carbureted combo tested, it was time to swap over to fuel injection. To that end we replaced the Edelbrock intake and Holley carburetor with a 90mm FAST LSX intake and matching 90mm MSD throttle body. The FAST LSX intake was run with a set of 36-lb injectors and a Wilson billet fuel rail, though the stock rail would be more than sufficient at this power level. Naturally, the FAST LSX induction system was run with a FAST XFI management system. Westech's Ernie Mena had the system up and running in record time and after a few quick power pulls, we were rewarded with impressive peak power numbers. Obviously the 5.3L combination responded well to the FAST LSX intake combination, as the little LS motor thumped out 482 hp at 6,600 rpm and 436 lb-ft of torque at 5,300 rpm. The FAST intake improved the power output everywhere compared to the carbureted combination, but the EFI combination would require an expensive management system or its stock or other aftermarket equivalent. From a cost standpoint, the carbureted combination would ultimately be less expensive, but it is hard to argue with the extra horsepower and torque offered by the FAST LSX combo.

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Normally the story would end here with our carb vs. computer comparison, but 482 hp seemed ever so close to the magical 500-hp mark. Looking down into our bag of tricks, we found a few that might help us at least get closer to the elusive 500hp number. Remember, the 5.3L short-block was bone stock, which meant we were still running a static compression ratio of roughly 9.5:1. A bump up to 10.5:1 would likely get us to 500 hp or at least very close, but a compression hike was not in the cards. With all of our hard parts and tune previously optimized, we turned to a trio of tried and true racing tricks, namely cooling the water temperature, lightweight oil, and some VP Q16 (oxygenated) fuel. Motors always make more power when the oil is hot and the water temperature is cold. Lightweight oil helps minimize frictional losses and the power required to drive the oil pump, while the Q16 race fuel increased the number of oxygen molecules to the motor. More oxygen equals more power. With minimal dyno time available, we threw everything we had at the motor at one time and were rewarded with (drum roll) 501 hp and 452 ft-lb of torque. Imagine a stock short-block 5.3L producing 500 hp with just a set of off-the-shelf Trick Flow 205 heads, a streetable hydraulic roller Comp cam, and FAST LSX intake (and a few strip tricks).

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Trick Flow Specialties
Tallmadge, OH 44278
Comp Cams
Memphis, TN 38118
Demon Engines
Sante Fe Springs, CA
L&R Automotive
Sante Fe Springs, CA 90670
Holley Performance Products
Bowling Green, KY 42101