Mopar Performance Engine - Building A 383 Stroker Part 2

Porting the Heads and Intake
We originally ordered the unported version of the EZ heads with the standard size ports so we could run the motor with a standard port Victor manifold. We had run the Victor intake manifold with the Edelbrock heads in the last dyno test and were quite happy with the results. But some discussions with different engine builders, combined with a few quick dyno pulls, convinced us the standard port heads and intake were not going to be happy with our big cam. The big cam killed the torque at lower speeds, while the smallish heads and intake manifold didn't allow the motor to come alive on the top end. We've since learned our lesson. It was a classic case of mismatched components, so we pulled the heads off and sent them to Jeff Kobyiski at Modern Cylinder Head (MCH). Jeff is well known in SS/AA circles as the guy who makes Hemi heads and intakes really work, but he also has CNC porting programs for Indy and Edelbrock wedge heads.

The CNC program that Modern Cylinder Head uses for the EZ heads resulted in a finished intake volume of 308 cc on our heads, which made it about halfway in between the Indy choices of 295 cc and 325 cc. But the MCH version does not require external oiling or the use of offset rocker arms so it is a little easier to install. The CNC machining of the combustion chambers makes them slightly larger, but after a quick cut of the deck they are back to 75 cc, so the compression ratio stays the same. Final flow-bench numbers after the heads were finished up showed them flowing 340 cfm at .600-inch valve lift on the intakes, and 224 cfm on the exhaust side at the same .600 lift. This is about 50 cfm more than the Edelbrock heads flowed the last time we tested, so the potential to pick up some power was there.

With the heads opened up to Max Wedge size, we needed an intake manifold to match. There aren't a lot of choices for a low-deck Max Wedge intake since this was never a factory option, but Indy has tooled up a manifold to cover this option. PN 400-2 is one we purchased since we were planning on running a 950 Ultra HP Holley carb. Indy also has a version of this manifold with the big Dominator carb flange for you drag race guys. Since any intake manifold can always use a little help, we sent the brand-new manifold to MCH, along with the heads, for some plenum blending and port matching.

Valvetrain
We ordered our EZ heads from Indy without springs since we had a complete top end kit from Competition Cams ready to put to work. Comp provided us with a set of their premium flat-tappet cam valvesprings, as well as titanium retainers, 10-degree Super Locks, and assorted spring cups and shims. The valvesprings were the top-of-the-line springs designed for flat-tappet cams in the .600- to .650-inch lift range. Since we were planning on running our cam with both 1.50- and 1.60-ratio rocker arms, these springs were a perfect match for us. The springs were installed in our heads at 200 pounds of seat load, which is quite high for a flat-tappet cam, but that is exactly what the folks at Schubeck recommended.

While we were on the phone with Comp, we also ordered a set of their Pro Magnum roller rocker arms. These Comp rocker arms have been around for several years and have proven to be tough enough to handle most big flat-tappet cams as well as many roller springs. They are made from 8650 chrome-moly steel, which is significantly stronger and tougher than aluminum. The Comp arms do not have a bushing at the shaft, but this doesn't seem to be a problem if the maximum spring pressure is kept below 500 pounds. If you're going to put the rocker arms under loads higher than that, you may wish to talk to the engineers at Comp to see what they recommend.