In the magazine industry, when we look back at past tech articles, we usually find something new we need to do, either to fix a mistake we made or just improve an existing great combination. Usually, we hope the latter applies, but it doesn't always work out that way. In our January 2004 issue, we changed from a mildly ported set of 906 heads with 2.14/1.81-inch valves to the Indy SR 295s on a 10.0:1 compression 440. We definitely experienced an increase in peak power at 5,600 rpm, 67 to be exact. During our baseline dyno pulls with the 906 heads, we observed power gradually dropping off after 5,600 rpm, and rapidly dropping when valve float occurred at 6,150 rpm. At 6,000 rpm, the Indy's were worth 90 rwhp over the 906s. We soon realized the particular flat-tappet hydraulic cam we used for the head-swap shootout wasn't a good match for the high-flow/high-rpm capabilities of the Indy heads. It was time to revisit the engine and step up to the next level of performance-a solid street roller cam.
Though it is more expensive to upgrade the valvetrain with a new cam, lifters, springs, different length/stronger pushrods, timing set, bronze distributor gear, cam button, and possibly rockers for a roller cam, a roller cam will add air velocity through larger-than-stock-size ports like those in our Indy's. The roller cam's lobes have more area under the curve and are beneficial to broaden the power band on a street-driven car. Looking through the Comp Cams catalog, we decided on an Extreme Energy solid street roller cam kit. For the sake of comparison, the hydraulic flat tappet was a decent stick (.533 lift w/1.6 rockers, 244 duration at .050-inch, and 110-degree lobe separation) next to the roller cam. Speaking of the roller, the cam we chose has some extra lift and duration, .576/582 lift w/1.5 rockers, and 248/254-degrees of duration at .050-inch on a 110-degree lobe separation to be exact. We feel this will add the high-rpm power the Indy heads are known to make. by going to a roller cam, an added bonus is duration at .050-inch lift can be increased by as much as 8 degrees, yet you can still expect similar idle and drivability characteristics-as long as the lobe separation is the same.
In an effort to keep all things as basic as the typical do-it-yourself cam swap, we didn't degree-in the roller cam to the cam card (though we should have). once the rocker arm geometry was confirmed, we ordered the proper length pushrods from Comp Cams. After the new valvetrain was installed, we set the cold lash .002-inch tighter than specifications. After 100 miles of break-in time with two oil changes and dyno testing, the hot lash was checked, and we were good to go. This same type of Comp Cams solid street roller valvetrain has been in our '67 R/T test mule for over 10,000 miles and eight years. the lash is checked every 1,500 to 2,000 miles, but the settings don't change. We live in good times today with the availability of high-quality valvetrain components compared to the stuff from over 25 years ago.
The Roller To The Rollers
Thanks to SLP Performance Parts owner and founder Ed Hamburger (Hamburger's oil pans), a date was set at their state-of-the-art Superflow SF840 chassis dynamometer. Our hydraulic cam baseline was previously recorded on their dyno (this means the numbers are in their computer system). For a fair cam test, no changes were done to the 440 or the drivetrain, except for the cam and components. We reused all the same parts- heads, intake, carb, ignition, tuning, converter, gearing, and so on. We only wanted to see the bump in power the new bumpstick would demonstrate.