440hp Budget-Built Vortec Small-Block

07. We've found the 750-cfm... 

   

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07. We've found the 750-cfm Edelbrock Performer to be an excellent fuel-metering system for high-performance street use. Although it's ultimately not as tunable as a modular-style carb, ours ran great right out of the box on this relatively mild motor. Should you need to tweak the mixture, the metering rods are readily accessible and available from Edelbrock. The carb's $219.95 price tag (Summit Racing) kept within our budget.

Although we'd already eclipsed the $2,000 mark, we still needed a carburetor and distributor. Edelbrock's 750-cfm square-bore Performer carb set us back a little over $200, and a stock HEI we had lying around filled the hole out back (new GM HEIs are about $200). Our dyno-test exhaust consisted of 13/4-inch long-tube headers with 31/2-inch collectors emptied into 3-inch pipes, terminated with three-chamber Flowmaster mufflers. It's probably overkill for this motor, but we used what we had.

Dyno-op Steve Brule strapped the Mouse onto Westech's Superflow dynamometer, hooked up the vitals, and fired it up. We were rewarded with good oil pressure, a lumpy, controlled 850-rpm idle, and snappy throttle response from the box-fresh Edelbrock carb. After a merciless afternoon of flogging, we'd richened up the metering rods, swapped to 1.6 rockers, and installed a 1-inch open spacer for a cumulative gain of 14 peak horsepower (442 hp at 5,900 rpm) and a couple lb-ft of peak torque (452 lb-ft at 4,400 rpm). Dollar for dollar, it's the bargain of the century that retains enough tire-shredding cojones to surely elevate your status at the cruise-in.

08. The initial dyno-testing...        read full caption 08. The initial dyno-testing revealed that the Edelbrock carb was a little lean, so Brule swapped out the stock 7147 metering rods for a thinner-tipped 6842 set, and we gained a little power and torque from optimizing the air/fuel ratio. The numbering convention is easy to understand: Take our original 7147 rods as an example. The end of each metering rod is tapered, so the numbers reflect the dimensions of the tip from its thickest to thinnest point. The "71" refers to the 0.071-inch diameter of the shank of the tip, and the "47" means it tapers down to 0.047 inch at the very end.

09. In the never-ending quest...        read full caption 09. In the never-ending quest for power, we swapped the stamped-steel 1.5:1 rockers for full 1.6:1 aluminum rollers. Original equipment on the limited-run LT4 engine, these rockers utilize the self-aligning design required for the Vortec heads. As shown on the dyno graph, the 1.6 rockers really let the engine breathe at high rpm, and we saw impressive gains in power and torque.

Dyno Results
Don't be swayed by the stingy budget; this Vortec-headed Mouse cranks out enough power and torque to be right at home between the framerails of a stout street machine. We didn't want to dig into the engine too deeply, and concentrated on making cost-effective improvements to the combination. Although we witnessed a notable increase in power after swapping to 1.6 roller rockers and adding the Wilson Manifolds 1-inch open spacer, the mill is plenty capable (and several hundred dollars cheaper) in baseline tune.