The block was machined so the piston was right at the top of the cylinder. dish pistons we
After carefully considering the parameters of our contest and the specifics of his combina
While a windage tray wasn't utilized, Scott did control oil return by routing oil away fro
Schurbon manufactured a stud girdle for the rockers in-house, keeping the valves under con
Tightening the valve lash freed up a few horsepower, indicating this engine could have mad
Since each engine was filled to the pan's capacity with Amsoil, engine builders couldn't r
Upon inspecting this engine after its dyno pulls, its durability was apparent. The bearing
Like most competitors, Schurbon relied on an accurate MSD distributor to ignite the fires, and he also kept costs down by using a Pioneer harmonic balancer. For induction, a Mopar single-plane intake manifold was matched with a 750-cfm 4150 series Holley that was modified by AED. When asked about porting the intake manifold, Scott states, "We didn't go crazy. we just used masking tape to keep the gaskets in place and port matched the intake to the heads." While we have a feeling Scott had more than just masking tape in his bag of tricks, this is a good example of how the proper combination can be just as effective as exotic parts and machine work. This engine is a proven performer, and we'd love to have it in one of our cars.
We congratulate Schurbon Engine and Machine on their second place finish in the '07 Engine Challenge.
Dyno Testing and Correction Factors
When testing engines on a dyno, there are several things to keep in mind. First, a dyno is a manufactured piece of equipment, so no two are identical. This inconsistency is minimal, however, as most dyno manufacturers claim no more than a one-percent difference between any two of their machines. Next, an engine on a dyno is subject to the same environmental inconsistencies as an engine in a car, so if the weather is hot and the barometric pressure is low, the engine will make less power. For this reason, dyno manufacturers utilize sophisticated software to monitor atmospheric conditions and correct for them so that each engine is measured to the same standard, regardless of the weather. The dyno software will apply a correction factor to the measured power numbers, adjusting them accordingly for non-standard weather conditions.
There are several correction factor standards commonly used by dyno software, and these too can be inconsistent. Correction factors can vary as much as four-percent between the correction factor that gives the most power versus the correction factor that is stingiest. For this reason, engine builders commonly dyno and rate their engines based on the correction factor that shows the most power, while research facilities are more worried about consistency. Comp's research facility uses the latest SAE (Society of Automotive Engineers) correction factor, which is considered stingy by most. So while all the engines in our contest would have likely shown more power if a more generous correction factor were used, using the SAE correction factor for all the engines made the playing field even and the contest fair.
Regardless of the weather or the correction factor used, there are other important considerations when dynoing an engine or a car. Each dyno cell is also different, and these differences aren't easily corrected for. Turbulent air, exhaust leaking into the cell, and other factors can make dyno readings between dynos somewhat ambiguous. So the moral of the story is this: Dyno numbers are really only valid when compared to numbers from the same dyno.