Swapping the cam means freshening the remainder of the valvetrain as well.
The new cam better matches our new heads, EFI, and goals.
The old cam served us well for almost eight years.
A hydraulic roller offers a broader power curve than a comparable flat tappet profile due to faster valve opening and closing rates.
With engine components from diverse brands, degreeing our cam is wise.
Crane's Tune-A-Cam kit includes a dial indicator, stand, piston stop, lightweight checking springs and more.
Next up, we'll drop in the engine and mock up the Holley HP EFI system. We're ditching the return style regulator.
Here’s a useful exercise: Consider how a cam swap might address a specific performance flaw such as poor mid-range torque.
Everyone’s getting in on the track day craze. Hotrodders are even migrating from the street and strip to road courses across the nation. There’s strong evidence of the shift here at Grassroots Motorsports as our staffer Camaro morphs from street machine to track day toy. It will still be street legal, but we’re tuning the combination to improve off-corner acceleration at the track instead of cruising. We’re also switching from a carburetor to electronic fuel injection. For many reasons, camshaft specs need to be reviewed. Rather than simply picking the largest, meanest, fire breathing camshaft available, we decided to bone up on the subject of cam specs. We won’t bore you with obvious parameters such as lobe lift. Instead we hope to help you carry an intelligent conversation with your cam grinder or engine builder.
Armed with a goal and vehicle specs, we turned to camshaft specialist Chase Knight at Crane Cams for a recommendation. The man has an ungodly grasp of engine tuning. Here’s a useful exercise: Consider how a cam swap might address a specific performance flaw such as poor mid-range torque. You might seek better idle quality for the street, or more peak horsepower. Is your engine running out of steam at the end of a straight? Is your engine bogging off a corner? The most valuable tuning tool is your current baseline combination. Regardless of what you drive on track, a simple cam change could be worth half a second per lap.
We presented Crane Cams with the following baseline specifications:
1968 Chevy Camaro
3330 lbs
406 gen 1 small block Chevy
4.155” bore x 3.750” stroke
10.5:1 compression ratio
Dart Pro 1 Platinum 200cc aluminum cylinder heads
2.020” x 1.600” valves
64cc combustion chambers
3.73:1 differential gears
25.5” diameter rear tire
Tach indicated RPM range (using Gingerman Raceway in South Haven MI): 2600 to 6600 rpm
Here’s the old and new cam specs for comparison:
——————
OLD CAM: Crower Hydraulic Roller
230°/236° @ .050”, .545”/.555” 110° LSA
NEW CAM: Crane Hydraulic Roller
232°/236° @ .050”, .539”/.548” 108° LSA
——————
Before you bust out your best Keyboard Kung Fu, remember that these two camshafts are supposed to be similar. We’re tuning. The old cam worked well enough. A big change, therefore, would make us feel sad. Furthermore, the subtle cam change is in conjunction with other new components like better flowing Dart Pro 1 Platinum aluminum heads and Holley HP Series EFI. The sum yields a net dynamic effect comparable to even more duration, but without the pesky side effects at low revs.
According to Chase, With the wide lobe separation angle: Intake event starts later / Exhaust event starts earlier. The result is less overlap. With a narrow lobe separation angle: Intake event starts earlier / Exhaust event starts later. The effect is more overlap.
We’re expecting about 510 horsepower from this combination. That’s 1.25 horsepower per cube. We can’t wait to fire up our freshly rebuilt small block Chevy and measure results in the real world.
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