Muscle Motors 431Temp: 51 degrees; humidity: 39 percent; barometer: 30.18Car and driver pounds: 3,780
Note: 28-inch slicks were mounted on 15x7 Centerline rims, reducing weight 40 pounds; 26-inch slicks were on 15x7 cop rims.
Yes, that's air under the left front tire.The borrowed pair of 28x9s helped us get our 431 stroker to hook up at the track. | 
We wanted a stronger street-and-strip combination to replace the outdated 383. We updated with a Muscle Motors 383/431 stroker kit. We topped it off with Edelbrock Performer RPM heads and intake. | 
Our 383 was sitting in R/T Dan's basement for the last 15 years. Our planned 383/431 will make more power than the typical 383-to-440 swap of 10-plus years ago. There are still plenty of inexpensive 383s (the most mass produced big-block) out there waiting for a buildup. |
Here's the 383/431 rotating assembly from Muscle Motors. The big arm of the kit is the 3.750-inch stroke, 4340-chromemoly steel crankshaft. It features 383 main journals, chamfered oiling holes, micro-polishing, and is precision balanced to the reciprocating assembly by Muscle Motors. I-beam steel rods (good for 600 hp) swing the forged aluminum Ross pistons (MM also balance equalizes the rods and pistons). High-quality Childs and Albert rings and Clevite 77 bearings round off this package. | 
We flowed the out-of-the-box Edelbrock heads before we touched-up the ports. At .600-inch lift, the aluminum castings flowed an average of 284 cfm through all eight ports. After porting and polishing, they flowed 301 cfm at .600-lift. | 
Here's an obstruction in the intake port that only needs .040 inch removed. Be careful not to remove too much metal-the head bolt hole is right behind there! We gained 3-4 cfm just by grinding half of that lump away. |
On the exhaust port (shown here), we blended farther in the bowl area and the CNC gasket matching (at the exit end) Edelbrock had already performed. We straightened and blended the CNC exit by going in another inch. Then we polished the entire port. A gain of 13-14 cfm at .600-lift made the work worth it. | 
We used the closed chamber (84cc) Eddy heads instead of the open chamber-type (88cc) heads. We thinned down the diameter of the valveguide boss (right), and bowl blended farther into the port. Here we picked up roughly 5 cfm at .600 lift. | 
On the (left) port, we removed about .080-inch from the pushrod pinch area. We also straightened the CNC gasket matching area. Notice how you can see more of the valveguide boss on the left port. This handiwork rewarded us with another 4-5 cfm at .600-lift. |
We polished both the intake and exhaust ports with extra attention at the short turn. We left the floor of the intake ports rough so the fuel droplets could tumble and atomize before entering the combustion chamber. |  | 
Edelbrock's Performer RPM intake is a proven-power-producer for both street and dual-purpose machines. It provides plenty of torque, throttle response, and power up top. We couldn't leave ours alone and went to work on it. We smoothed out the plenum entrance to the runners, all the dividers, turns, port roofs, and walls. The plenum waffles and the floor of the runners were left as cast to promote efficient fuel atomization. Otherwise, all else was polished for added velocity and throttle response. No port matching was done. |
The block was square decked to provide a piston-to-deck height of only .005 inch. The boring process and then honing with deck plates brought the holes to .030-inch over for a final bore diameter of 4.280 inches. The static compression ratio is right at 10.0:1 with the 84cc heads for pump gas compatibility. The Ross pistons feature deep valve reliefs for clearance of high-lift cams (over .600-inch lift). Notice the nice crosshatch pattern in the bores from the final honing-that promotes good ring seal for power production. | 
We used Milodon's high-volume pickup (PN 18325), windage tray (PN 32000), and popular 7-quart, low-profile oil pan (PN 30930). We prefer Fel-Pro's pan gaskets (Summit PN FPP-1834) to prevent pesky oil pan leaks. A Mopar Performance high-volume oil pump (Summit PN DCC-4286590) completed the lubrication system. | 
It wasn't necessary for our particular build to clearance-grind the bottom of the cylinder bores for rod-bolt clearance (we had over .150-inch clearance). The block was line-bored, and the rods checked for size to ensure proper clearances for the bearings. Notice the ARP main studs and the rods feature ARP fasteners for a reliable bottom end. |
For a maintenance-free valvetrain, we chose a hydraulic cam. It's a roller-type stick with a faster valve lift curve than a flat-tappet cam. This allows more air and fuel to enter the cylinder to make more power. Crane's PowerMax cam (PN 689531) and roller lifters fit the intended power range (2,200-6,400 rpm) for the build. The bumpstick features .528/.539-inch lift and 230/236 degrees of duration at .050 inch, with a 112-degree LSA (lobe separation angle). The interior of the block was coated with Glyptal (Eastwood PN 46001Z) to aid in oil drain back. | 
We set the hydraulic lifter preload at a 11/42-turn past zero lash. The entire valvetrain and timing set was from Crane Cams. Our B-motor used the roller tip rocker assembly (PN 64790), pushrods (PN 64628), and valvesprings (PN 99890-16). During dyno and strip testing, we didn't experience any valve float revving the engine to 6,500 rpm. | 
Be sure there's enough oil pressure (see the gauge at rear of motor), and you can visually see the oil flowing out of each rocker onto the valve tips and pushrods. While pre-lubing, it's best to turn the engine over (socket and breaker bar attached to the crank bolt) to fully lube the rod, main, and cam bearings. |
On the left is the bronze distributor gear with the hardened oil pump driveshaft (Milodon P21525). A bronze gear must be used with a roller camshaft. The steel gear/shaft (right) is used with flat-tappet cams. Fast revving motors with a high-volume oil pump require the hardened shaft. Did you ever experience a stock shaft snapping, causing a total loss of oil pressure? On a street-driven car, it's also good to check the bronze distributor gear for wear every few thousand miles. We've seen them wear out completely. | 
Up top is the Holley 950HP and Wilson Manifolds carb spacer. We couldn't use the spacer due to hood clearance. We mounted the tti 131/44-inch headers and the no-name chrome valve covers (Summit PN SPE-5277) so we could custom make the length of the Pertronix 8mm Flame Thrower ignition wires (straight and angle boot). We also trial fitted the fuel line and coil relocation bracket (from Fabulous Fabrications) to mount the Pertronix Flame Thrower coil. The balancer is an indexed, SFI-approved damper from Summit (PN SUM-B64279). |  |
Anticipating over 100 more horsepower, there's no way we would expect the stock rubber engine mounts to hold up to the tremendous torque. We ordered Schumacher Creative Services new Poly Loc mounts (left). See the cut-away mount (center). The Magnum Poly Loc mount contains a unique internal interlock mechanism that prevents mount blow out. | 
The original throttle cable (top) was too short to work with the Holley 950HP carb (the 383 had an 800-cfm Edelbrock) and taller than stock intake. Imperial Services hooked us up with the longer throttle cable (bottom). It's actually a reproduction for the '63-'64 Max-Wedge. | 
The tti headers bolted right up to the 8-year-old, 3-inch exhaust. These tubes (PN tti 838440-134C5) feature a polished ceramic outside coating with a thermal barrier inside for many years of service. |
When we began dyno testing, we were happy to gain a 100 rwhp over the old 383 (see charts). That was at only 32-degrees total timing. Next, we advanced the timing to 36 degrees to realize 2 hp and a bunch more torque (29 lb-ft). At 39 degrees, we lost a few horses so we went back to 36 degrees. All in all, we gained 102 rwhp and 133 rwtq. | 
At the track, the old load-leveler shocks worked fine with the less torquey 383. Baseline 60-foot times with the 431 showed us a slightly spinning, 1.67-second, 60-foot time. We bolted on the new QA1s, set them at 6 clicks, and saw the 60-foot drop to 1.64 seconds with no spin. On the front, the QA1s were set at zero clicks for the full 90/10 feature. For the ride home, the fronts and the rears were set 8 clicks and 2 clicks, respectively. | |