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Edelbrock Heads - 467 Hp With A 425ci Olds

Who Needs A Long Stroke When You Can Have 540 lb-ft Of Torque And Make

Photography by Terry McGean

After the cam was sufficiently run in, Westech's Steve Brul took the 425 to 5,500 rpm several times as he and White figured the tune. Total timing seemed sweetest at 34 degrees, and once the air/fuel was dialed, the 425 made 444 hp at an even 5,000 rpm. The 516 lb-ft maximum torque reading seemed to be on the downslope of torque curve, but it's a safe bet that the peak happened just prior to 3,500 based on the 5,000-rpm horsepower peak. We wondered what a traditional-style square-bore carb would do, so the Q-Jet was swapped for a 750-cfm Speed Demon. After minor tuning, the 425 responded with 456 hp at 5,100 rpm and 526 lb-ft at 3,600.

The Edelbrock Performer manifold is a nice unit but a bit closer to stock than we'd like to see for this combination. A Performer RPM would have been perfect, since they almost always boost upper rpm power without sacrificing anything, but for some reason, Edelbrock doesn't make one for the big Olds. A Torker would be a good alternative; we ran one on our 455 and squeezed out another 20 hp, but we couldn't lay our hands on one in time for this session. Instead, we tried a one-inch carb spacer-one of Wilson's tapered-combo designs that uses a four-hole configuration topside that blends into an open plenum underneath. It was good for five additional horsepower and pound-feet of torque. Swapping for a traditional open spacer reduced these gains by about half.

Westech has a set of Hooker Super Comp headers in its arsenal that feature 2-inch primaries, so we figured they were worth a try. We swapped them on along with a pair of 311/42-inch straight-through Race Magnum mufflers, but power gains were a mere 2 hp, and torque barely nudged up by a similar amount. Apparently, this engine didn't need bigger headers.

Any Regrets?When it was over, the Westside crew was pretty stoked with their Olds. It did what it was supposed to, making a hearty horsepower number at an rpm level that didn't jeopardize the hardware, and it had a mega-fat torque curve. Even with the 108-degree lobe separation on the cam, the idle-vacuum readings at 850 rpm were in the range of 16.5 inches-plenty for a street machine. We wished we'd had another intake-there's almost definitely more power in there, but that'll have to wait. One area that will be addressed before the engine is run again is oil control, as our test revealed that the stock pan was allowing the crank to whip the oil into a froth, sapping power and compromising oil pressure in the upper rpm range. We'll revisit the 425 once it's installed in the Cutlass for evaluation and to watch Navid deal with his newfound traction deficiency.

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