Godbold thinks it would be revealing to do the same test with a much smaller set of three cams in the same application. "Then I think you would see a wider power range on the wider separation cam," he observed. "I still think 107 would give you the best peak numbers, but the wider separation cams tend to fall off less beyond peak power." With smaller cams running at a lower rpm, we'd probably be able to see that. But for now, we've got a very clear demonstration of the advantages-namely a more usable powerband-of running a narrower LSA.
Dual Plane
Because we were in effect...
Because we were in effect testing bigger and smaller camshafts by changing the lobe separation angle, we wanted to see how our trio would work with both single- and dual-plane intakes. We tabbed Dart for both models, and both preferred the 107-degree LSA camshaft.
The Holley 950 Ultra HP we...
The Holley 950 Ultra HP we used for our dyno sessions at Westech had no provision for taking a vacuum reading, so we installed a 1-inch spacer with a port so we could measure vacuum for each cam. The differences were minimal. The three cams were separated by 3 inches of vacuum.
| LOBE SEPARATION ANGLE EFFECTS |
| NARROWER LSA | WIDER LSA |
| Increased overlap | Reduced overlap |
| Increased low-rpm torque | Improved top-end power |
| Narrower powerband | Wider powerband |
| Reduced idle quality | Improved idle quality |
| Increased cranking compression | Reduced cranking compression |
| Decreased piston-to-valve clearance | Increased piston-to-valve clearance |
| 406 STROKER SPECS |
| Displacement | 406.0 ci |
| Bore x stroke | 4.155 x 3.750 |
| Rotating assembly | Probe forged steel crank |
| | and rods |
| Pistons | Probe forged |
| Heads | Dart Pro 1 227 CNC |
| Compression | 11.1:1 |
| CAMSHAFT 1 |
| 107º LSA Comp Cams Hydraulic Roller |
| PN | 12-000-8 |
| Grind No. | CS 3318S/3319S HR107+4 |
| Gross valve lift | 0.562/0.580 intake/exhaust |
| Valve lift w/ 1.6 rockers | 0.600/0.619 intake/exhaust |
| Duration at 0.050 | 248/254 intake/exhaust |
| Valve timing (@ 0.050 lift) | Open | Close |
| Intake | 21 BTDC | 47º ABDC |
| Exhaust | 58 BBDC | 16º ATDC |
| Vacuum at 1,000 rpm | 6 in |
| CAMSHAFT 2 |
| 110º LSA Comp Cams Hydraulic Roller |
| PN | 12-444-8 |
| Grind No. | XR300HR |
| Gross valve lift | 0.562/0.580 intake/exhaust |
| Valve lift w/ 1.6 rockers | 0.600/0.619 intake/exhaust |
| Duration at 0.050 | 248/254 intake/exhaust |
| Valve timing (@ 0.050 lift) | Open | Close |
| Intake | 18 BTDC | 50º ABDC |
| Exhaust | 61 BBDC | 13º ATDC |
| Vacuum at 1,000 rpm | 7 in |
| CAMSHAFT 3 |
| 113º LSA Comp Cams Hydraulic Roller |
| PN | 12-000-8 |
| Grind No. | CS 3318S/3319 HR113+4 |
| Gross valve lift | 0.562/0.580 intake/exhaust |
| Valve lift w/ 1.6 rockers | 0.600/0.619 intake/exhaust |
| Duration at 0.050 | 248/254 intake/exhaust |
| Valve timing (@ 0.050 lift) | Open | Close |
| Intake | 15 BTDC | 53º ABDC |
| Exhaust | 64 BBDC | 10º ATDC |
| Vacuum at 1,000 rpm | 8 in |