A combination of solid engine building and creative interpretation of the rules landed Ind
We all know that an engine dyno can be a useful tool for finding horsepower while tuning a performance engine. Let's face it though, engines don't propel dynos, they propel cars. Since the rules of our Engine Challenge require a minimum of three qualifying pulls through the full 3,000- to 7,000-rpm range, followed by a minimum of three judged pulls, we ensure the contest engines aren't just dyno mules built only to last a couple of pulls, but real engines that can survive the abuses of cruising around town, highway driving, and making passes at the dragstrip. Because we also wanted to make certain the engines in our challenge are typical of engines our readers can afford to run in their cars, we factor the cost of the parts that went into the engine into the power the engine produces for a power-per-dollar rating.
This year, our Engine Challenge featured the small-block Mopar powerplant and displacement was limited to 410 ci. We were certainly impressed by the diversity of these potent small-blocks, and even more impressed by the power they made running on 93-octane Rockett Brand pump gas. These engines proved to be durable, powerful, and economically built, epitomizing the intent of our competition.
This month, we'll take a look at the first place engine of Indy Cylinder Head and the second place engine of Schurbon Engine and machine to see what parts and techniques each of these builders utilized to finish well.
Indy Cylinder Head
It takes power, durability, and a cost-effective combination to be competitive in our Engine Challenge, and Indy Cylinder Head had just the right mixture of the three to score a win this year. Though better known for their high-flowing, aluminum cylinder heads and big, cubic-inch race and street engines, engine builder Ken Lazzeri stated that the way our contest rules factor costs, building an economically priced, cast-iron-headed engine just made more sense than going for all-out power. Earning a win in this year's challenge proved his theory right-the Indy entry made just enough power to finish decimals ahead of the second place engine.
In our closest competition to date, Indy Cylinder Head scored a win with their powerful, e
Using conventional tuning techniques, engine builders Ken Lazzeri and Russ Flagle carefull
Wiseco pistons, Eagle I-beam connecting rods, and Clevite rod bearings formed a solid foun
While externally, the Indy entry looked just like any other Magnum-headed small-block, internally these guys pulled out all the stops. A factory 360 block was bored .030-inch oversize, and then filled with an Eagle cast crankshaft, Eagle I-beam connecting rods, and Wiseco Pro True flat-top pistons for a displacement of 408 ci. A factory Mopar oil pan was utilized in conjunction with a Milodon windage tray and Sealed Power oil pump to ensure everything stayed lubricated during the dyno pulls. The parts they selected worked well as the engine performed flawlessly while on the dyno, and the bearings looked like new after multiple pulls to 7,000 rpm.
A Milodon windage tray was utilized to keep oil off the rotating assembly, and a factory p
Atop their engine's solid bottom end, Indy resisted the urge to utilize a set of their aluminum race heads, using Magnum R/T cast-iron cylinder heads instead. Stating that the Magnum head is hard to beat for the cost, these heads were treated to some very cool in-house tricks, which greatly added to the power this engine produced. To keep the valvetrain light, hollow/sodium-filled intake and exhaust valves from the new-generation Hemi engine were utilized. Since these valves have a shorter stem length than factory Magnum head valves, the crew at Indy actually remachined the combustion chamber of the head so the valves would work. Since they were machining the combustion chamber anyway, they CNC machined the head's combustion chambers to the chamber found on their popular 572-13 cylinder head. Knowing our rules prohibited welding or epoxy modifying the cylinder head, they machined the pushrod "pinch" area of the port to a larger size, and then pressed in a brass sleeve to seal the pushrod area and increase the width of the intake port for improved flow. Hand porting was then performed in-house to optimize the flow characteristics of the cylinder heads.
Since the rules prohibited welding or epoxy modifying their heads, Indy pressed in brass s
Using lighter valves from the new Chrysler Hemi meant the combustion chambers had to be re
Port shape was optimized in-house by good old-fashioned manual porting with the help of a
Indy used several tricks to find incremental horsepower gains, including under-driving the
Multi-layer steel head gaskets were used to keep the combustion chambers sealed. We've fou
Indy used their own rocker arms with Comp "beehive" valvesprings to keep the valve gear un
To optimize power from this potent small-block, the Indy crew used a Comp solid flat-tappet camshaft and Indy rocker arms to actuate the valve gear. Comp "beehive" springs kept the valves under control at rpm, and an MSD distributor fired the cylinders. An Indy single-plane aluminum intake matched with a Demon 850 four-barrel carburetor took care of induction, and Schoenfeld headers expended the burnt gasses. To save costs, factory valve covers were used, along with a factory timing cover and oil pan. Overall, this engine made great power from economical hardware, and we really enjoyed seeing the crew from Indy optimize an engine that didn't wear Indy heads. We congratulate Indy Cylinder Head for winning the '07 Amsoil/Mopar Muscle engine challenge.
|Diamondback Engines||Indy Cylinder Head|
|7723 FM 723||8621 Southeastern Ave.|
|Richmond, TX 77469||Indianapolis, IN 46239|
|Mid America Racing Engines||MRL Performance|
|1945 W. 18th St.||4651 Culley Ln.|
|Washington, IA 52353||Jackson, MI 49201|
|Muscle Motors||R.M. Competition|
|2085 Glenn St.||28648 Maple|
|Lansing, MI 48906||Roseville, MI 48066|
|Schurbon Engine and Machine||Speed-O-Motive|
|203 S. Clark St.||131 W. Lang Ave.|
|Maquoketa, IA 52060||West Covina, CA 91790|
Narrowly missing a first place finish, the Schurbon Engine and Machine entry made nearly 5
Schurbon Engine And Machine
When we spoke with Scott Schurbon of Schurbon Engine and Machine at the beginning of our contest, he stated he would bring a strong engine, but wouldn't sacrifice reliability for power. Scott said his engine would be one just like he would sell his customers, and he wouldn't use cheap parts simply to place better in the contest. During the dyno portion of the challenge, it was apparent this engine was not only a strong performer, but also had the potential to place very well in the contest. Scott and his crew effectively tuned their entry to more power on each pull, even swapping to a smaller, less expensive carburetor without losing power. This engine sounded strong and smooth, and performed flawlessly allowing Scott plenty of time to tune his engine to nearly 500 hp and a stump-pulling 460 lb-ft of torque!
Everyone agreed that the Schurbon entry looked great wearing its Plum Crazy purple paint job, and it performed as good as it looked once on Comp's dyno. Inside their factory 360 block, Scott utilized an Eagle cast-crankshaft, RPM connecting rods, and Probe pistons to net a displacement of 410 ci. A standard volume Melling oil pump was matched with a Moroso oil pan, but we noticed the absence of a windage tray in this engine. When asked why, he stated the windage tray would have to be modified to work properly, and he simply ran out of time before the engine had to be delivered to the Mopar Nationals so he welded baffles into his oil pan instead. Even with no windage tray, this engine performed flawlessly and had no oil-related issues while making its dyno pulls.
To top his short-block, Scott used cast-iron Magnum cylinder heads that were ported in-house for optimal flow. Since this is a street engine, Scott decided not to overdo it when it came to port volume and camshaft. He says he likely left a little on the table as a larger cam would have made more power, but at 460 lb-ft of torque, this engine would perform great in a street car. Inside his cylinder heads, Scott used extreme-duty, stainless steel valves and Comp springs. A Comp solid flat-tappet camshaft actuated the valve gear through Scorpion roller rocker arms. Scott manufactured a stud girdle for the rockers in-house and had no problems spinning his engine to the required 7,000 rpm. A factory Mopar timing cover and Mopar aluminum valve covers were used to keep costs down.
The Schurbon entry performed flawlessly, allowing the crew to try multiple tuning techniqu
During his qualifying pulls, engine builder Scott Schurbon sensed something just wasn't ri
Probe pistons and RPM connecting rods, along with an Eagle crankshaft, formed the foundati
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.