The design of the 280 lift cam is presented in Table 5 and Figs. 12 through 15. In all respects, this camshaft is intermediate between the improved stock and Laurel-Roof camshafts. The intake and exhaust centerline angles and the angle between the lobes is the same as a stock cam. The duration of the intake and exhaust valve openings is intermediate between the other two cams. The intake valve opens at the same angle as the Laurel-Roof cam and two degrees before the improved stock cam. The intake closes one degree before the Laurel-Roof cam and two degrees after the improved stock cam. The exhaust valve opens six degrees before the improved stock cam and ten degrees after the Laurel-Roof cam. The exhaust valve closes six degrees after the improved stock cam and three degrees before the Laurel-Roof cam. The ramp velocity is relatively mild, i.e. similar to that for a stock cam at a valve lash of 0.013. The maximum velocity in this design is restricted to 0.0083 in/deg (0.475 lifter radius) to insure that stock Model T lifters can be used. The value of R_b + L_max = 0.682 for the exhaust lobe and 0.737 for the intake lobe. The exhaust lobes will pass freely through the holes in the block. The intake lobes are 0.050 inches larger than the holes in the block, but will install without requiring notches. This cam should produce excellent performance for stock and slightly warmed engines.

Table 5

280 Lift Camshaft Specifications

Intake Duration and Ramp Velocity

Exhaust Duration and Ramp Velocity

Figure 12. Comparison of 280 cam intake (thick lines) with stock cam

Figure 13. Comparison of 280 cam exhaust (thick lines) with stock cam

Figure 14. Shape of 280 cam intake lobe

Figure 15. Shape of 280 cam exhaust lobe