L84 Fuelie Motor On Engine Dyno - Fuelie Fisticuffs

The Carbed L76 Takes On The Injected L84 On An Engine Dyno

Richard Holdener Nov 1, 2009 0 Comment(s)
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When was the last time you saw a Rochester fuel-injection system on an engine dyno?

Just a few short years after Chevy introduced the original 265 small-block, the company followed up by offering a true legend in the form of the fuel-injected 283. Often touted as the first mass-produced motor to offer 1 horsepower per cubic inch, the fuelie 283 started a small-block Chevy performance trend that would continue for decades. The 283hp 283 of 1957 was eventually replaced with Chevy's new wonder motor, the 327. Compared with the 283, the 327 offered an increase in both bore (from 3.875 to 4.00 inches) and stroke (from 3.00 to 3.25 inches). Continuing the performance trend started a few years earlier, Chevy topped the hot 327 with the latest version of its mechanical FI setup. The pinnacle of this combination was the famous L84 fuelie motor that offered no fewer than 375 hp in 1964 and 1965.

Whereas the fuelie 283 offered 1 hp/ci, the L84 sported an amazing 1.146 hp per cube. In fact, until the release of the quad-cam LT5 in the ZR1, the L84 was the highest-rated production small-block ever offered by Chevrolet. Of course, there's a major difference between the gross power numbers of the muscle-car era and the modern net-rated versions. Gross ratings were obtained on an engine dyno under ideal conditions and without accessories. The current net ratings comply with SAE standards and are taken at operating temperature, using the factory tune, and with full accessories, induction, and exhaust (including catalytic converters). Thus the 375hp L84 is likely closer to 325 hp by today's more exacting standards.

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Though the L76/L84 engines were originally equipped with two-bolt blocks, our test 327 started out with a four-bolt piece courtesy of L&R Machine. L&R honed and bored it 0.030 over to make way for a new set of forged pistons.

Looking at the specs of the L84, you can see that the 327's power came courtesy of an elevated compression ratio, a set of high-performance heads, and aggressive cam timing. Back in the days of high-test fuel, factory motors could get away with a combination of iron heads and the 11.0:1 compression offered in the L84. Similarly, the L84's hairy solid-lifter cam yielded a crotchety low-speed idle that wouldn't be tolerated in the modern era. Whereas lesser motors offered 1.94/1.50 valves, the "double hump" fuelie heads (461 castings) sported a larger 2.02/1.60 combination. Of course, the main reason anyone purchased the L84 was the Rochester FI system. Interestingly, other than the fuelie induction system, the L84 was the same motor as the carbureted, 365hp L76.

Sales figures indicate that the L76 was much more popular than the L84. There are two distinct reasons for this, the first being price. While the L76 cost just $129 more than the base engine, the fuelie motor tacked on a whopping $538, or $246 more than the 425hp 396! Another factor was that fuel injection was completely foreign to most enthusiasts at the time. In fact, a great many fuelie owners removed the injection setup altogether and replaced it with a single- or dual-quad combo for street/strip racing.

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Sorting through their many available cores, the L&R crew were able to locate a suitable 3.25-inch 327 crank to fit our large-journal block.

The popularity of the carbureted engine and the general inaccuracy of the output ratings of the time gave rise to an interesting question: What was the real difference in power between these legendary small-blocks? Did the L84 really produce 10 more peak horses than its carbureted sibling? If so, what was the difference in power elsewhere along the curve? And what about fuel metering? Did the injected combination improve the air/fuel curve compared with carburetion?

The Hardware
To accurately answer these questions, we needed to first build a suitable test motor. We decided to assemble not just a small-block, but something that would replicate the original 327 combinations of 1965. This meant an 11.0:1 327 equipped with period-correct cylinder heads, a reproduction of the original solid-lifter cam, and the factory high-rise intake. Obviously we also had to have an original Rochester FI system on hand to compare to the carbureted combo.




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