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It's All In Your Heads
It's always nice when you can rely on your neighbors for a helping hand-especially when you're shooting for a big hairy horsepower number and your neighbor just happens to be cylinder head maestro Air Flow Research. Add in the success that Latimer had with his first 327, and it was a given that AFR would get the call for this project. AFR's Tony Mamo suggested a set of the company's 195cc Competition Ported Eliminator heads. That's right, even though emphasis here was on high-rpm horsepower, the parties involved weren't willing to entirely kiss off the lower end and wanted a better balance. And that's where the Competition porting job comes into play. Most of us hear "competition porting" and think WOT, max-rpm power. But a motor is never just at its peak. It's always moving through the rpm range, even when it's at full throttle. In that case, ultimate high-end performance is not necessarily the main reason for choosing Comp porting. "It's always best to run a smaller head that reaches your CFM target or goals, especially in any application that spends a fair amount of time on the street," explained Mamo. "When you have the same airflow through a more conservatively sized port, the torque and the low/midrange power is a lot stronger, and the snap and crispness in part-throttle operation is vastly improved, a factor you will never see measured or quantified on a dyno, but that's very welcome once you experience it." Well, couldn't they just have put a bigger head on it? Negative, said Mamo. With the 210 street heads, you'd save $500 but end up with a lazier engine and without the linear power curve. "I always recommend Comp porting to anyone who's serious about what they're doing," Mamo elaborated. "It does it all better: It has higher airspeed for better cylinder fill, it improves low/midrange torque and power output, it has better throttle response, and it improves fuel economy-it's just more efficient."  Although headers with larger-diameter...  Although headers with larger-diameter tubes were tried, best results were achieved with Hooker 1 3/4-inch Super Comp long-tubes, fitted with 18-inch extensions.  A peek down the valley during...  A peek down the valley during an intake change revealed the Comp solid-roller lifters, as well as the Manley 5/16-inch pushrods. These pieces have a 0.080-inch-thick wall for improved valvetrain stability. And while many 195cc runner heads match up to a Fel-Pro 1205 intake gasket, AFR's Mamo pointed out that the Comp ported head is closer to the larger 1206 gasket.  We already mentioned that...  We already mentioned that best power numbers were obtained with the black ported intake-fitted with a stack of phenolic spacers. The four-hole spacer was added first to add to the plenum volume; the potent 327 picked up about 6 hp.  A tapered combo spacer was...  A tapered combo spacer was then added to this intake sandwich. This type of spacer helps get the mixture flow out of the carb, filling in dead air spots and eliminating backswirl, according to Mamo. This one picked up another 2 hp. Latimer's Chevy II has a cowl hood on it, so he can actually fit these spacers underneath if he chooses to.  Two carbs were used on this...  Two carbs were used on this 327, and the highest horsepower number was obtained with this AED Performance 950 HO carb. AED buys unmachined castings from Holley, then does all its machining in-house, does precise parts matching, and installs its own fuel curve and calibration, among other features. The 950 HO actually uses a 750-cfm HP body combined with an 850-cfm baseplate. Real-world flow, according to AED, is 825 cfm. The larger baseplate allows airflow for power up top, while the smaller body enhances responsiveness since the venturi controls the signal to the boosters.  The AED mixer came out of...  The AED mixer came out of the box with 78 primary jets and 86 secondaries-this 327 liked things on the lean side for its most powerful dyno pulls, so the front side was pulled back four sizes to 74, while the secondary side was cut back two sizes to 84.  To obtain a compression ratio...  To obtain a compression ratio in the 11.5:1 range, the heads were milled down 0.030 inch, reducing the chamber size from 65 cc to an even 60 cc. About the chamber: Mamo called it an "efficient heart-shaped design that helps low and midlift flow." Below about 0.400-inch lift, the chamber is more important than the port in promoting flow, since the mixture must get past the valve. After that, the valve is farther away, and the chamber is less critical.  According to AFR, its Comp...  According to AFR, its Comp ported heads feature a finer level of CNC work, allowing for entirely accurate reproduction of the original port design. This is evident in the intake ports, which also feature a ramp or air dam of sorts in the intake bowls, which Mamo said "does some very beneficial things for the airflow curve in general." Never one to mince words, he added, "It's the most efficient port design out there in a medium-sized 23-degree cylinder head."  The exhaust ports also receive...  The exhaust ports also receive the same precise CNC treatment as the rest of the head, but lack the wings found on the intake side. They do, however, have a generous short term to allow the burnt junk an unhindered exit path.
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