Chevy Small-Block 327 Outputting 462 Horsepower
The Other Small-Block
Richard HoldenerWriter
Jan 1, 2013
In a world of small-blocks where bigger is better, the 327 still gets a lot of respect. Compared to the original 265, the 327 was obviously larger and more powerful, but where the 327 fell short was after the introduction of the larger 350. The 350 had more torque and a production lifespan that endured for decades until the end of the Gen 1 SBC.
Despite being down on inches to the 350, the 327 Chevy still lays claim to the most powerful production conventional small-block ever produced, the L84. Rated at 375 hp, the fuel-injected 327 was a high-winding screamer, as satisfying to drive as any big-block. At the other end of the spectrum, the 327 was also offered at much more pedestrian power levels, as low as 210 hp (gross). Regardless of the original output, the 327 (like any small-block), is a solid foundation for a performance build up. Like many of you, we still love the 327 and wanted to do a quick buildup with one.
Loyal readers will remember that some time back, we included the 327 in our salute to the legendary small-blocks. Taking a look back through the pages of history, we built and tested a number of the most popular and powerful small-blocks from yesteryear, including the DZ302, the LT-1 350 and the L76 327. Those of you who didn't catch the results can look online at superchevy.com—it makes for good reading.
The borrowed fuelie heads and expensive factory dual-plane, high-rise intake were all returned, but the upshot of all that testing was that we were left with a healthy 327 short- block just begging for upgrades. For those just tuning in, the short block used to simulate the 365hp L76, included a four-bolt block, a 3.25-inch (cast) crank and forged domed pistons that produced the requisite 11.0:1 compression ratio with 64cc chamber heads.
The idea behind this story is to provide a route for increased performance for 327 owners. The best way to demonstrate the merits of our modifications was to compare them to a known baseline. Given the vast number of different 327 configurations available over the years, it was difficult to pinpoint the ideal candidate. For this test, we simply relied on the L76 numbers generated previously for our legendary small-block series.
The 365hp 327 configuration served as a high water mark for factory motors, so our baseline motor was best case scenario. With the exception of the injected L84, every other factory 327 would start out producing less power than the L76, making the gains offered by our proposed modifications that much more impressive. Equipped with the legendary fuelie heads, hot Duntov cam and aluminum high-rise intake, you might think this combination would be tough to beat.
Well, time and technology have marched on since the introduction of the L76 and though it was certainly hot for its day, modern cams, intakes and (especially) cylinder heads offer huge power gains over their factory counterparts. Despite the 365hp rating offered by Chevy, run on the dyno, our L76 327 reproduction produced peak numbers of 353 hp and 368 lb-ft of torque.
As mentioned, our 327 featured domed pistons designed to produce a static compression ratio of 11.0:1. For our build we took full advantage of the elevated compression, but know that the heads, cam and intake package described here work equally well on any low-compression 327-equipped with flat-top pistons. The pistons will require valve reliefs to work with the Comp solid lifter cam.
With a healthy short-block at our disposal, we set off to improve the power output by making changes to those components most responsible for power production, namely the heads, can and intake. As good as the factory components were back in the day, the new stuff is so much better. Off came the L76 heads, cam and intake, replaced by components from AFR, Comp Cams and Procomp Electronics. The key to the success of any build up is to make sure the components were all designed to produce power in the same rpm range. Only working together will they optimize power production. Miss with just one component and the combination will suffer.
We started off with the cylinder heads. Compared to modern heads, the original fuelie heads were both down on flow and up on weight. Chevy never successfully offered aluminum heads on any of the small-block motors back in the day, but they are certainly the hot ticket for performance now. Our heads came from AFR, and where the stock heads had trouble exceeding 210 cfm on the flow bench, the AFR heads flowed 100 cfm more. In fact, the exhaust ports of the heads flow more than the intake on the factory fuelie heads.
What the massive head flow did for our combination was allow us to produce exceptional power without resorting to wild (unstreetable) cam timing. The heads featured full CNC porting, a 2.08/1.60-inch valve package and 66cc combustion chambers to slightly lower the static compression ratio.
In addition to a significant drop in weight and tremendous flow, the aluminum heads also reduced the chance of harmful detonation. Capable of supporting over 600 hp in normally aspirated trim, our relatively mild 327 was not taking full advantage of what they had to offer. These heads were chosen as much for what the 327 might become in the future (think stroker) as its current configuration.
Next on the list was cam timing, and here we actually took a step backward, at least in total duration. In truth, our cam selection from Comp Cams was significantly more powerful than the Duntov 30-30 cam, despite a drop in duration at 0.050. Though hydraulic roller cams are all the rage, in keeping with the old-school nature of the 327, we stuck with a solid flat-tappet grind. Compared to the 254 degrees of duration offered by the Duntov cam, the still healthy 236/242-degrees offered by the Xtreme Energy grind seems tame, but there is much more to cam than simple numbers. The Comp cam also offered a 0.501/0.510 lift split, a 110-degree LSA and a recommended lash adjustment of 0.016.
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