With a cylinder head mounted to the block, the scale of the Arias/Shelby conversion heads
Up top, Trefz originally built the engine with a custom sheetmetal intake manifold, however the AMSOIL Engine Masters Challenge competition requires a cast intake manifold. To fulfill this requirement, an Edelbrock Yates single-plane was substituted. Trefz tells us, “I had to make a last-minute change to the cast manifold to meet the event rules, and it definitely showed a loss of power. The intake swap cost us about 100 hp in testing, so that was disappointing. With more development time on the manifold, the question is just how many of those horsepower we could have gained back. I literally got the manifold bolted on and tested the day before leaving for the event, and was disappointed by the power loss, but loaded up and went to the competition.” The crew at LTR did have some time to mildly modify the intake, reducing the cross-sectional area with epoxy filler added to the floor to improve velocity, and mildly massaging the plenum area. An open adapter spacer mates the intake’s 4150 flange with a BRE-modified Holley 1150 Dominator carb.
Oil drain back from the top end is assisted by a pair of drain provisions in the cylinder
Rounding out the engine combination, a CRS electric water pump circulates the coolant without paying a tariff in power, while an ATI Superdamper is mounted to the nose of the crank just below to keep crank harmonics in check. Ignition is provided by all MSD components, centering on a deadly accurate MSD crank trigger signaling an MSD Digital 7 ignition, with the HVC II coil, ProBillet distributor, and wires all also from MSD. Handling the exhaust are stainless steel headers from SPD, using 2-inch primary tubes and a tri-Y–style collector. The bottom end is sealed by a custom full-length Stef’s oil pan holding just 7 quarts of AMSOIL 0-20 synthetic motor oil. As Trefz tells us, “I decided that a big deep oil pan would keep the oil away from the crank and had the idea of using a big, deep, full-length pan. I called Stef’s to have it built, thinking I was onto something, and as soon as I began explaining what I wanted, they said they had already built a dozen pans just like that for the Engine Masters Challenge.”
The Arias rocker arrangement is a work of art, with bulletproof investment-cast 4340 steel
The engine certainly garnered the attention of everyone in attendance at the 2011 AMSOIL Engine Masters Challenge on looks alone. The Arias/Shelby conversion heads and aluminum Shelby block gave the engine a captivating exotic look that emphasized the engine’s performance potential. Despite outright peak power that was well down on the more developed combination using the custom sheetmetal intake manifold, the 427-cube Shelby effortlessly ran through the rigors of the Challenge, while delivering a peak output of 748 hp. That’s exotic output for any naturally breathing 427-cube engine.
“You can make a great street engine from a race engine, but you can’t make a great race engine from a street engine.” —Nick Arias Jr.
“Capping the cylinders is the crowning jewel of the combination, the Arias/Shelby cylinder heads.”
“The valve angles allow for a much smaller chamber volume than older Hemi designs…”
Looking at the head from the chamber side, the true hemispherical shape of the Arias/Shelb
LTR originally built the engine with a custom sheetmetal intake manifold. To meet the Engi
With a custom Contreras cam measuring .810-inch lift, the valvetrain must be made up of to