The Amsoil/Mopar Muscle Engine Challenge - Chenoweth Speed And Machine

To see video of Chenoweth's dyno run click here.

The annual Amsoil/Mopar Muscle Engine Challenge is a favorite subject here at Mopar Muscle because it gives us a chance to share so much great information with our readers. Since this year's contest featured a 440 spec motor, all of the builders had to use the same Indy SR cylinder heads, and their 440s were limited to a maximum .060 inch overbore and stock stroke. Additionally, all the engines had to run on the same Rockett Brand 93 octane pump fuel while on Comp's dyno, limiting the compression of most engines to around eleven to one. With rules such as these, our top finishers had to find incremental ways to optimize their engines' power and were forced to get pretty creative. This month, we'll go inside Chenoweth Speed and Machine's engine and show you just how they achieved their 695.8 hp and 567.3 lb/ft of torque for a combined score of 1263.1 and a third place finish in the Amsoil/Mopar Muscle Engine Challenge.

Known for their expert machine shop service, and for products such as their big-block main stud girdle and block-in-a-bag service, Chenoweth was expected to perform well during our competition. Engine builders Dale and Mike Chenoweth stated that they treated this engine like any other leaving their shop, using all new top quality parts and precise machining techniques, and didn't cut any corners simply because it was a dyno contest engine. They also didn't choose to bore their engine to the maximum size allowed by the rules. Since their block cleaned up at .030 inch oversize, they decided to stop there rather than boring to .060 inch over just to net a few additional cubic inches. This will allow the block to be taken to the next oversize if necessary during a future rebuild.

So how did Chenoweth Speed and Machine achieve nearly 700 hp from their pump gas 440? Starting with a factory block with a casting date of April 1977, they treated their block to Chenoweth's full "block-in-a-bag" machining service which includes completely cleaning the block, boring and honing the block with plates, decking and squaring all surfaces, bushing the lifter bores, and line boring the main journals. Once the machining was complete, a 440 Source 3.75 stroke forged crank and H-beam connecting rods were matched with a set of Diamond forged flat-top pistons, and the entire rotating assembly was precision balanced. Diamond moly piston rings were utilized and the Chenoweths used Clevite bearings throughout their engine. To keep the crank solidly in place and to prevent the main caps from "walking" during high-rpm operation, the Chenoweths bolted on one of their CRE Main Stud Girdle kits with a dipstick and pickup provision. We've used the main stud girdle kit before and have found it's a great way to tie the main caps to the oil pan rail, giving the mains an additional plane of support in high-horsepower applications.

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.