When it came to choosing a camshaft for this engine, Mike and Dale Chenoweth decided to be somewhat conservative. Knowing this engine would run on pump gas and likely end up in a street car, they decided to sacrifice peak numbers slightly to broaden the power and torque curves of their engine. Though not small by any means, the Comp .660-inch lift solid roller cam had 252/263 degrees of intake and exhaust duration respectively. Installed at a 108 centerline and spun by a Pro-Gear double roller timing set, this cam did make peak power right at the contest limit of 7,000 rpm. To finish off their short-block, the Chenoweths used a stock timing cover and ATI balancer. To keep everything lubricated, a Melling standard volume oil pump was combined with a Milodon PN 30931 oil pan, a custom made crank scraper, and a Milodon single-line external pickup and oil pump cover.
Since this year's Engine Challenge featured spec engines, all the competitors were required to use the same Indy SR cylinder head. Starting with a level playing field, each engine builder had to look for incremental gains through porting and valve work to gain an advantage. Chenoweth Speed and Machine utilized Indy's CNC ported version of the SR head and did additional port work in-house to optimize flow. Manly stainless steel valves, PN 11380 intake and PN 11381 exhaust, were utilized and the valves and seats were treated to a custom valve job. Comp PN 947-16 valvesprings were utilized, and Harland Sharp rocker arms with a 1.7 intake and 1.6 exhaust ratio actuated the valves. Since their Comp cam was .660 inch valve lift based on a 1.5 rocker ratio, the 1.6 and 1.7 ratio rockers actually made valve lift .748 inch on the intake side and .704 on the exhaust side. Smith Brothers custom pushrods combined with Comp solid roller lifters were used for their durability. For induction, the Chenoweths chose an Edelbrock PN 2893 Super-Victor intake, topped with a Quick Fuel prepped 1050 Dominator carburetor. During their dyno pulls, however, they changed to an 1150 Dominator carb and gained a few horsepower. To ignite the mixture, an MSD PH 8546 Pro-Billet distributor was utilized along with a modified intermediate shaft with a Torrington-style bearing. Hooker PN 5209-1HKR headers handled expelling the spent gasses.
|Indy Cylinder Head||Chenoweth Speed and Machine|
|Indianapolis, IN 46239||Morton, IL, 61550|
|Schurbon Engine and Machine||Cederstrand Racing Engines|
|Maquoketa, IA, 52060||Brea, CA, 92821|
|JMS Racing Engines||Promax|
|El Monte, CA, 91732||Indianapolis, IN 46222|
|JD Engine and Machine|
|Columbia, MO, 65203|
A Milodon PN 30931 oil pan...
A Milodon PN 30931 oil pan was utilized and modified with an additional baffle to keep the oil in the pan and off the rotating assembly.
The Indy SR heads require...
The Indy SR heads require external oiling provisions from the back of the block. This allows bigger intake ports and more flow.
For a lifter valley cover,...
For a lifter valley cover, the Chenoweths fabricated their own from clear polycarbonate. While it didn't add any power, it sure was cool to watch the lifters and pushrods doing their thing while the engine made its dyno pulls.
We noticed that the Chenoweths...
We noticed that the Chenoweths not only under-drove their water pump, but had a loose belt on it as well. By not spinning the pump as fast, there was less parasitic loss of horsepower.
Cometic multi-layer-steel (MLS) head gaskets were utilized in this engine. We've used these ourselves and found them to seal the cylinder as well as O-ringing the heads and using copper gaskets, but without the extra machining expense.
Since this year's rules allowed...
Since this year's rules allowed only one cylinder head, Chenoweth Speed and Machine used the same Indy SR head as the rest of the competitors, treating them to custom port and valve work before bolting them in place.
By modifying an intermediate...
By modifying an intermediate shaft, the Chenoweths installed a Torrington-style bearing where the shaft touches the bushing in the block. Since the shaft also runs the oil pump, they state this bearing helps stabilize the shaft and distributor for more accurate ignition timing.
The Chenoweths chose Harland...
The Chenoweths chose Harland Sharp rockers with a 1.7 intake and 1.6 exhaust ratio to get more lift from their somewhat mild Comp roller camshaft.
Is Scott Schurbon sabotaging...
Is Scott Schurbon sabotaging the Chenoweth engine? Actually, he pitched in to help and offered his 1150 Dominator carb to gain the Chenoweths a few additional horsepower. Here he's using water to clean the combustion chambers while the engine runs before a pull, an old trick to gain a slight advantage.
This overlay shows the first...
This overlay shows the first and best pulls on the Chenoweth engine. As you can see, the torque curve is very broad and the engine peaked precisely at the 7,000 rpm limit of the contest.
To top their 440, an Edelbrock...
To top their 440, an Edelbrock Super Victor single-plane aluminum intake manifold was port-matched to the Indy heads and bolted in place.
At 695.8 hp and 567.3 lb/ft...
At 695.8 hp and 567.3 lb/ft of torque, Chenoweth Speed and Machine earned the top numbers until the final day of this year's competition. We congratulate them on their third place overall finish and thank them for participating in the 2008 Amsoil/Mopar Muscle Engine Challenge.