431 Stroker Buildup
The 431 Stroker Project came about through the decision to restore my Father-In-Law's 1968 Road Runner. It is numbers matching, so we didn't want to do a engine swap. But we wanted more torque and horsepower, without the loss of drivability. So the 431 Stroker Project was born. I immediately sent out a flurry of emails to the major piston manufactures. Only one came back with a positive response. Ron at Diamond Racing was eager to help us design a piston for our application.
The next step was to find out if other people are interested in doing this buildup. I started a Topic on Moparts.com to discuss the idea. There has been a lot of interest in the idea and a lot of great posts. Mopar people are very helpful. We were told about an article called the 451 Manifesto on www.arengineering.com. After studying it, I wrote an article on building the 431 Stroker. It can be viewed here. Building the 431 Stroker
Next we established our design parameters. We wanted a daily driver engine that produces good torque and mild performance, but look stock. Looks can be deceiving. Desktop Dyno put the Horsepower and Torque number at the HP440 level.
See the DESKTOP DYNO results.
Here is a list of the parts we have specified.
The Bottom End
The block is a 1968 HP 383, bored .030 with torque plate.
The crankshaft is a 1967 HP 440 forged unit that has had the mains cut down to 2.625 and the total diameter cut to 7.25". For added strength, a set of ARP main Studs were installed. For added oil leakage protection, an Indy Rear Main Seal was installed (the best $50 you can spend).
The rods are the OEM 383 Rods with ARP rod bolts.
The pistons are Diamond Racing Pistons for the Short Rod 383/431. They came with the 1.094" Piston Pins and Moly Rings.
A Mellings HV oil pump M63HV handles the lubrication.
The entire rotating assembly was balanced to 2348 grams.
The Valvetrain
Because this is a torque application and after comparing a bunch of camshafts on Desktop Dyno, we decided to use the Mopar Performance OEM Magnum camshaft (P4452783). It produced the largest Torque Number at a useable RPM range.
A Cloyes Double Roller Timing Chain was set to 4 degrees advanced to move the Peak HP down a little in the RPM Band.
440Source.com Chrome Moly Pushrods connect to new Mopar Performance Rocker Arms (P4529743) on 440Source.com Chrome Moly Rocker Arm Shafts.
The Top End
The Heads are the original 1968 "906" pieces. The exhaust guides were replaced. A set of Manley Race-Flo 1.81" Exhaust valves were installed.
The Valve Springs are Mopar Performance (P3690933)
ARP Head Bolts were installed.
The factory HP Exhaust Manifolds have been blasted and ceramic coated.
The factory HP intake manifold was not modified.
A vintage 1968 HP440 Carter Carb 4429S (750cfm) was rebuilt and installed on a 1/2" phenolic spacer.
Other Parts
A Mopar Performace Electronic Ignition will light the fire.
While a Flo-Kooler Water Pump will help with the cooling.
The entire engine was painted with Bill Hirsch - Turquoise engine paint. http://www.hirschauto.com/
Then it was topped off with the OEM Air Cleaner and a new "Red" 383 Road Runner Pie Tin.