After two years of testing and development, Andrews Products is offering cams for S&S gear drives for Twin Cam. The primary advantage is that the gear drives use less engine power to operate than stock chain drives. Dynamometer comparisons show gains of 4 horsepower over similar engines with chain driven cams. When less power is needed to turn the camshafts, more power gets to the rear wheel. For all out drag motors, there is also an additional advantage with gear drive cams. Simply stated, higher lift cams can be used with the gear drive setup. The reason for this requires some explanation. With chain drive 88 cams, valve lifts of .600 or higher will result in interference between front and rear cam lobes. With the gear drive cams, lobe top angles are different so lobe to lobe interference cannot occur. These cams are for use with S&S cam gear drive kit (fmc-721948).
| |
Open |
Close |
Duration@.053" Lift |
Valve Lift |
Lift@TDC |
Springs |
| 21G |
|
|
|
|
|
|
| Intake |
10° |
30° |
220° |
.498" |
.134" |
Stock |
| Exhaust |
40° |
08° |
228° |
.498" |
.121" |
|
| 26G |
|
|
|
|
|
|
| Intake |
11° |
35° |
226° |
.490" |
.138" |
Stock |
| Exhaust |
41° |
09° |
230° |
.490" |
.112" |
|
| 31G |
|
|
|
|
|
|
| Intake |
10° |
46° |
236° |
.510" |
.131" |
Stock |
| Exhaust |
52° |
08° |
240° |
.510" |
.120" |
|
| 37G |
|
|
|
|
|
|
| Intake |
14° |
42° |
236° |
.510" |
.151" |
Stock |
| Exhaust |
48° |
12° |
240° |
.510" |
.140" |
|
| 50G |
|
|
|
|
|
|
| Intake |
20° |
48° |
248° |
.510" |
.184" |
Stock |
| Exhaust |
54° |
18° |
252° |
.510" |
.168" |
|
| 55G |
|
|
|
|
|
|
| Intake |
22° |
46° |
248° |
.550" |
.197" |
Stock |
| Exhaust |
52° |
20° |
252° |
.550" |
.181" |
|
| 59G |
|
|
|
|
|
|
| Intake |
29° |
57° |
266° |
.590" |
.238" |
Hi-Lift |
| Exhaust |
63° |
27° |
270° |
.590" |
.218" |
|
