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With nearly 750 normally aspirated horsepower from their 427-cube Arias/Shelby combination, LTR’s team (from left to right) of Joe Felciano, John Garrison, and team leader Lanny Trefz are justifiably proud of their first effort at the Engine Masters Challenge competition.
By The Numbers
427ci Windsor Ford
Arias Hemispherical Head Conversion |
| Bore: |
4.125 inches |
| Stroke: |
4.00 inches |
| Displacement: |
427 ci |
| Compression ratio: |
14.4:1 |
| Camshaft: |
Contreras solid roller |
| Camshaft duration: |
268 degrees at .050-inch tappet rise |
| Valve lift: |
.810 inch |
| Rocker ratio: |
Arias rockers; 1.82/1.75:1 ratio |
| Piston rings: |
Total Seal |
| Piston: |
Arias |
| Block: |
Shelby Aluminum Windsor |
| Crankshaft: |
Scat |
| Rods: |
Carrillo |
| Cylinder head: |
Arias Windsor Hemispherical |
| Intake valve diameter: |
2.250 inches |
| Exhaust valve diameter: |
1.600 inches |
| Intake manifold |
Edelbrock |
| Carburetor: |
Holley 1,150-cfm Dominator |
| Header: |
SPD 2-inch primary |
| Ignition: |
MSD Digital 7 and crank trigger |
| Damper: |
ATI |
| Fuel: |
VP Q16 |
| RPM |
TQ |
HP |
| 3,500 |
445.3 |
296.7 |
| 3,700 |
485.7 |
342.2 |
| 3,900 |
509.8 |
378.5 |
| 4,100 |
529.2 |
413.1 |
| 4,300 |
540.7 |
442.7 |
| 4,500 |
543.1 |
465.3 |
| 4,700 |
550.0 |
492.1 |
| 4,900 |
567.6 |
529.6 |
| 5,100 |
584.4 |
567.4 |
| 5,300 |
598.6 |
604.0 |
| 5,500 |
606.7 |
635.4 |
| 5,700 |
609.1 |
661.1 |
| 5,900 |
608.3 |
683.3 |
| 6,100 |
605.7 |
703.5 |
| 6,300 |
601.9 |
722.0 |
| 6,500 |
593.6 |
734.7 |
| 6,700 |
584.3 |
745.4 |
| 6,900 |
569.3 |
747.9 |
| 7,100 |
551.5 |
745.6 |
| 7,300 |
532.1 |
739.5 |
| 7,500 |
516.4 |
737.4 |
 Looking at the head from the...  Looking at the head from the chamber side, the true hemispherical shape of the Arias/Shelby heads is revealed. The relatively shallow 74cc chamber is achieved by using a valve angle of 15 degrees (intake), and 16 degrees (exhaust). An alternate chamber design, the Arias/Shelby “Pro Stock” style chamber, is available at 67 cc, and features filled-in quench areas at each side of a figure eight chamber configuration.  LTR originally built the engine...  LTR originally built the engine with a custom sheetmetal intake manifold. To meet the Engine Masters Challenge requirement for a cast intake, an Edelbrock 2961 Yates manifold was reworked, but power was well below that of the custom intake. Fuel is supplied via a BRE custom 1150 Holley Dominator.  With a custom Contreras cam...  With a custom Contreras cam measuring .810-inch lift, the valvetrain must be made up of top quality parts. The valves are Ferrea and measure 2.250 inches (intake) and 1.600 inches (exhaust). Beefy Manton pushrods are moved by Isky solid-roller lifters, while the PSI valvesprings deliver 380/1,010 pounds of closed/open load. The cam features 268 degrees duration at .050 inch, and a lobe separation angle of 112 degrees.  The manifold received epoxy...  The manifold received epoxy filler in the runners to help reduce the cross-sectional area for more port velocity. Trefz tells us the stepped mismatch (where the runner meets the large intake ports of the head) does not represent a problem, and even helps reduce intake tract reversion.  To provide an unwavering spark,...  To provide an unwavering spark, the engine is equipped with an MSD crank trigger to generate the ignition signal, while an MSD Digital 7 ignition provides the spark. The MSD Pro Billet distributor serves only to deliver the secondary voltage to the appropriate plug.  A beautiful set of stainless...  A beautiful set of stainless steel headers from SPD handles the exhaust via a 2-inch primary tube diameter and a tri-Y collector configuration. For the Engine Masters Challenge competition, these headers were routed to a pair of Flowmaster mufflers.
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