A top view of the short-block...
A top view of the short-block shows the Diamond flat-top pistons in position. The block was decked until the pistons were almost flush with the top of the block. we left the slugs .005-inch down in the cylinder. Having the pistons at zero deck puts the compression ratio at 10.0:1 with the Edelbrock heads and a standard .030-inch thick gasket.
Switch To Edelbrock Heads, A Victor Intake, And Racer Brown Rocker Arms
The dyno results with the 906 heads were decent for such a simple combination, but we felt the need to bolt-on a few more modern parts in search of even more power. We had a set of Edelbrock aluminum heads that were last used in the Jan. '05 article titled "Manifold Power." The heads had been lightly ported by Dwayne Porter at Porter Racing Heads for that article. After his rework, the heads flowed 290/220 cfm at .600-inch lift. These Edelbrock heads have beehive springs from Competition Cams installed on them, and we installed a set of 1.6/1.5 rocker arms from Racer Brown to pump up the power a little more. While we were at it, we also bolted on a Victor 383 manifold to replace the M1 manifold from the previous tests. The short-block remained identical between the head tests as did the headers, carb, oil system, and ignition.
Since the camshaft has already been broken in, we were able to get right back to testing once the head swap was complete. The head swap was fairly easy to accomplish on the dyno since all of the parts other than the head gaskets were re-used. The Edelbrock heads are stock replacement heads, so the same head bolts, pushrods, rocker arms, and so on will swap directly across.
Once we had the bolts all tight, the little 432 responded by cranking out 507 lb-ft of torque at 5,100 rpm and 545 hp at 6,200 rpm. So the peak torque stayed about the same between the two different heads, but the Edelbrock combination allowed us to carry the torque curve higher for an additional 45 peak horsepower. In a bracket car, that extra power on the top end would be very noticeable, and the reduced weight on the front of the car would just be icing on the cake.
Conclusion...For now
Overall, we're happy with how this little 432-inch motor turned out. These new Diamond Racing pistons seem just the ticket to get some new life out of an older 383 block that might be sitting neglected in the corner. If a person really wanted to make a stock-looking, big-block A-Body, we bet a set of cast-iron heads could be ported to flow well enough to make a real stock-looking powerhouse. If you went down that path you could have a healthy 550 horse big-block that looked stone stock. Now that would be fun!
 We tried both the cast-iron...  We tried both the cast-iron 906 heads, as well as aluminum Edelbrocks on our 432. The 906 heads had Isky 1.50-ratio nodular-iron rocker arms, while the Edelbrock heads used the new 1.6/1.5 ratio setup from Racer Brown. |  We wanted to make sure the...  We wanted to make sure the cam timing stayed where we set it and still be adjustable when needed. We installed the cam with a Cloyes Hex-a-just timing set. The billet timing chain cover allows us to easily adjust the cam timing without having to remove the damper. |  One trick Super Stock racers...  One trick Super Stock racers employ are these Schubeck lifters. They are expensive, but when used on the dyno, if you need to test a bunch of different cams, they really pay off. There is no break-in required, and you can re-use them over and over again on different cams. |
 With the cast-iron heads and...  With the cast-iron heads and M1 intake manifold bolted-on, we're ready to head to the dyno. We used a Milodon cover on the stock oil pump, so we can run a remote screen type oil filter. We use the electric water pump for dyno sessions since it's quick and easy to hook up. |  The Edelbrock heads are ready...  The Edelbrock heads are ready to bolt-on right out of the box. They are a closed-chamber design, which provides a quench area for improved combustion. We outfitted our heads with beehive valvesprings (PN 26120) from Comp Cams, as well as Racer Brown rocker arms. |  This close-up shows the combustion...  This close-up shows the combustion chamber of the 906 head (right) and the Edelbrock chamber (left). Much of the Edelbrock chamber is flush with the surface of the head since it is a "closed" chamber design, while the 906 head shows a recessed or "open" combustion chamber. Closed, or quench-type, combustion chambers are designed to improve power and efficiency due to an increase of turbulence within the chamber. |
 We also used a standard tin-type...  We also used a standard tin-type intake manifold gasket with the Eddy heads and Victor manifold. The angled spark plugs on these heads didn't cause any problems with our dyno headers, but they can interfere with some passenger car headers, so check it out before you buy. |  Here is a sneak preview of...  Here is a sneak preview of what we'll be doing next with this 383 stroker. The 545 hp just wasn't enough, so we headed back to the dyno with a set of Indy EZ heads and a big Comp Cams bumpstick. Stay tuned, because it's going to be interesting. | |