During the '60s and very early '70s, Chevrolet had free reign over the performance of its muscle mouse motors. The high output 302, 327 and 350 small-blocks were all sporting 11.0:1 compression, big-valve heads and aggressive, solid-lifter cams. In short, they were serious performers that packed a powerful punch.
Loyal Super Chevy readers can verify this by referencing our Legendary Small-Blocks series, where we compared the powerful L76 327, the DZ302 and the LT-1 (September 2009), followed by the an article dedicated to the hydraulic-cammed powerhouses, namely the L79, the L46 and the L82 (March 2010). The L79, L46 and L82 all featured hydraulic-lifter cams, but what really separated the L82 from the other five performance small-blocks was the serious drop in static compression ratio. The pre-smog engines tested were offered with 11.0:1 compression, but the L82 made due with just 9.0:1.
The sizable drop came from a combination of flat-top pistons and large-chamber heads. A drop in compression from 11.0:1 to 9.0:1 will reduce the power output by eight percent or more, and the drop occurs across the rev range, not just at the power peak. This represented a serious kick in the teeth for Chevy enthusiasts looking for a performance machine during the disco era.
Naturally, things were much worse for owners of the lesser base model small-blocks, and the L82 was eventually killed off, signaling and end of the carbureted small-block performance era. Unfortunately for Chevy enthusiasts, you are unlikely to drop by your local wrecking yard nowadays and find an original motor from an LT-1 Z/28, L79 Chevy II or even an L46 Corvette begging for a home. In fact, you'd be hard pressed just to find a good set of high-compression performance cylinder heads, let alone a suitable short-block bolted under them. The rows and rows of Chevys not occupied by late-model four- and six-cylinder commuter cars might feature a handful of computer-controlled, carbureted small-blocks. If you can't find any small-blocks in the passenger cars, check out the section dedicated to full-size trucks. Carbureted small-blocks will be a dime a dozen there.
None of the car or truck engines will be of the legendary caliber, but don't be so quick to discount them. We're going to show you how to get muscle car-era performance from these smoggy small-blocks. Like our L82, the low-compression mills will respond just as well to some simple performance upgrades. Since we changed the heads, cam and intake on our L82, your starting point can be just about any low-compression mouse (meaning flat-top or slight dish pistons).
The upgrades we performed on this L82 test mule can be applied to any low-compression smog motor (including those using throttle body or tuned port injection). The reason we chose the L82 as our starting point is that we felt sorry for this much-maligned combo. After all, the L82 was saddled with just 9.0:1 compression and expected to perform against a pack of 11.0:1 motors. Now toss in the 882 heads (unfortunately notorious not for poor flow but for cracking), the cast-iron Q-Jet intake and matching carb and you have all the elements of a serious Cindefella story. All we needed was a hairy, fairy godfather sporting the latest performance hardware to transform the L82 into a serious baller. Glass slipper? Not this girl. Try Doc Martens, tribal tattoos and a tongue piercing.
Loyal readers will remember that the low-compression L82 was equipped with 882 heads, L46 hydraulic cam (0.450/0.460 lift, 222 duration) and an induction system consisting of a cast-iron intake and Q-Jet carb. The Q-Jet was actually less of a hindrance than you might suspect as the 750 cfm rating was more than adequate for the needs of the 250hp L82. In stock trim on our dyno, the 9.0:1 L82 produced 313 flywheel (gross) horsepower at 5,500 rpm and 355 lb-ft of torque at 3,800 rpm. The engine produced adequate torque relative to the horsepower rating, but it wasn't exactly what you'd describe as earth-shattering.
Replacing the stock 882 iron heads with 200cc RHS aluminum heads, an XE274H hydraulic flat-tappet cam and Pro Comp dual-plane, aluminum intake resulted in some serious power. Fed by a Holley 750 HP series carb (we should have tried a test with the stock Q-Jet-sorry), the upgraded L82 produced 414 hp at a slightly higher 5,900 rpm and 415 lb-ft of torque at 4,100 rpm. The upgrades to the L82 improved power throughout the rev range, from 3,000 rpm all the way to 6,500. The gains would be even greater on a milder small-block (from, say a truck) since the stock cam timing would be even milder than the L46 cam used in the L82.